chemistry...the total mark for this paper is 70. questions 1 and 2 are practical exercises each...

71

Centre Number

Candidate Number

6620.07R

TIME

2 hours 30 minutes.

INSTRUCTIONS TO CANDIDATES

Write your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all three questions.Write your answers in the spaces provided.

INFORMATION FOR CANDIDATES

The total mark for this paper is 70.Questions 1 and 2 are practical exercises each worth 25 marks.Question 3 is a planning exercise worth 20 marks.Quality of written communication will be assessed in Question 3.You may not have access to notes, textbooks and other material to assist you.A Periodic Table of elements (including some data) is provided.

For Examiner’s use only

QuestionNumber Marks

Modera-tionMark

1

2

3

TotalMarks

ADVANCEDGeneral Certificate of Education

2011

Chemistry

Assessment Unit A2 3Internal Assessment

Practical Examination 1

[AC231]

TUESDAY 17 MAY, MORNING

6620.07R 2 [Turn over

Teacher Examiner Remark

Mark Check1 Titration exercise

Crystalline ammonium iron(II) sulfate has the formula Fe(NH4)2(SO4)2.nH2O. The symbol n represents the number of molecules of water of crystallisation.

You are provided with:

A solution of ammonium iron(II) sulfate of concentration 31.4 g dm23.

A solution of potassium permanganate of concentration 0.02 mol dm23.

Solutions of 2 mol dm23 sulfuric acid.

Assuming that all the apparatus is clean and dry, you are required to carry out a titration and use your results to determine the value of n.

(a) Give details of the procedure you intend to use. The potassium permanganate solution should be placed in a burette.

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

_____________________________________________________ [6]



Mark Check (b) Carry out your procedure. Present your results in a suitable

table and calculate the average titre.

[10]

(c) State the colour change at the end point of your titration.

_________________________ to _________________________ [2]

(d) Write the equation for the reaction of iron(II) ions (Fe21) with acidified permanganate ions (H1/MnO4

2).

_____________________________________________________ [2]



Mark Check (e) Calculate the molarity of the ammonium iron(II) sulfate solution.

________________________________________________________

________________________________________________________

_____________________________________________________ [2]

(f) Determine the molar mass of the ammonium iron(II) sulfate and deduce the value of n.

________________________________________________________

________________________________________________________

________________________________________________________

_____________________________________________________ [3]



Mark Check2 Observation/deduction

Safety goggles must be worn at all times and care should be exercised during this investigation.

(a) You are provided with a salt, labelled A. Carry out the following tests.

Record your observations in the spaces below.

Test Observation Deduction

1 Describe the appearance of A.

[1] [1]

2 Add a spatula measure of A to approximately 50 cm3 of water and stir.

[2] [1]

3 Add 10 drops of silver nitrate solution to 2 cm3 of the solution of A in a test tube. Allow to stand. [2] [1]

4 Add 5 drops of sodium hydroxide solution to 2 cm3 of the solution of A in a test tube. [1] [1]

5 In a fume cupboard, add 6 cm3 of concentrated ammonia, slowly, to 2 cm3 of the solution of A in a test tube. [3]

No deduction required

6 Add 4 cm3 of concentrated hydrochloric acid to 2 cm3 of the solution of A in a test tube.

[1]


Deduce the name of compound A ______________________ [1]



Mark Check (b) Substance B is an organic compound with two functional

groups. Carry out the following tests on B and complete the table.


1 Describe the appearance of B.

[1] [1]

Below is a description of test 2. Please read this but do not carry out this test.

2 Heat one spatula measure of B in a test tube. Heat gently at first and then more strongly. Test any fumes with a glass rod dipped in concentrated hydrochloric acid.

White smoke

[1]

3 (i) Dissolve 2 spatula measures of B in approximately 20 cm3 of water.

(ii) Use Universal Indicator paper to determine the pH of the solution of B. [1] [1]

4 Add 6 drops of copper(II) sulfate solution, dropwise, to a test tube half-full of a solution of B.

[1] [1]

5 To 3 cm3 of acidified potassium dichromate solution add one spatula measure of B and warm gently.

[1] [1]



Mark Check


The infra-red and n.m.r. spectra of B are shown below. Note that the molecule of B has made an internal structural rearrangement. Use these spectra and the practical tests to suggest the identity of B.

Infra-red Spectrum

0.75

0.6

0.45

0.3

0.15

4000 3000 2000 1000

Wavenumber (cm�1)

Tra

nsm

ittan

ce

Hydrogen atoms attached to electronegative atoms such as N or O absorb in the region above 3000 cm21. The actual absorption region is affected by acidity and whether the IR spectrum is obtained for the solid or a solution of the substance.

The carbonyl group in ketones absorbs at 1720 cm21. All other compounds containing C=O groups absorb from 1580 to 1800 cm21.

N.m.r. spectrum

8 7 6 5 4 3 2 1 0

Identity of B __________________________________________ [1]

Maximum [25]



Mark CheckPlanning exercise

3 Preparation of sodium peroxide, Na2O2.

Sodium peroxide may be prepared by passing dry oxygen over sodium in a “boat” made of aluminium foil which is placed in a combustion tube. The tube is heated until the sodium melts. It is further heated until the sodium burns.

At this stage the heating can be turned down.

After reaction a stream of dry air is passed through the combustion tube. The resulting sodium peroxide is placed in a stoppered bottle and weighed.

The sodium peroxide is obtained as a white solid with a slightly yellow appearance. It reacts readily with water to produce hydrogen peroxide or oxygen depending on the temperature at which the reaction is carried out.

You are required to prepare 1.3 g of sodium peroxide based on the mass of sodium used.

(a) Write an equation, including state symbols, for the reaction of sodium with oxygen to produce sodium peroxide.

_____________________________________________________ [2]

(b) Calculate the mass of sodium needed assuming an 80% yield.

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

_____________________________________________________ [4]

(c) Explain why it is essential that the oxygen, which is passed over the sodium, is dry.

________________________________________________________

_____________________________________________________ [2]



Mark Check (d) Draw a labelled diagram of the apparatus used to prepare

sodium peroxide, showing how the oxygen gas may be dried.

[4]

(e) The sodium peroxide may be used to prepare hydrogen peroxide by reacting it with acids at low temperatures. Adding phosphoric (V) acid to sodium peroxide produces disodium hydrogenphosphate, Na2HPO4, which crystallises with twelve molecules of water.

(i) Write an equation for the reaction of phosphoric (V) acid with sodium peroxide.

_________________________________________________ [2]

(ii) Suggest why this method is better than using hydrochloric acid producing sodium chloride, which crystallises without molecules of water, to prepare a concentrated solution of hydrogen peroxide.

____________________________________________________

_________________________________________________ [2]

(f) Sodium peroxide reacts with water at higher temperatures to form sodium hydroxide and oxygen. Describe how you would use GLC to show that oxygen was given off.

________________________________________________________

________________________________________________________

_____________________________________________________ [2]

Quality of written communication [2]

THIS IS THE END OF THE QUESTION PAPER

Permission to reproduce all copyright material has been applied for.In some cases, efforts to contact copyright holders may have been unsuccessful and CCEAwill be happy to rectify any omissions of acknowledgement in future if notified.

111279

6620.06

General Certificate of Education2011

Chemistry



[AC231]


MARKSCHEME

6620.06 2 [Turn over

AVAILABLEMARKS

Annotation1. Please do all marking in red ink.2. All scripts are checked for mathematical errors. Please adopt the system

of one tick () equals [1] mark e.g. if you have awarded 4 marks for part of a question then 4 ticks () should be on this candidate’s answer.

3. As candidates have access to scripts please do not write any inappropriate comments on their scripts.

1 (a) Rinse burette and pipette with appropriate solution [1] place 25.0 cm3 (or specified volume) in conical flask using a pipette filler [1]

add acid (20 cm3 of dilute sulfuric acid) [1] swirl flask during test [1]add permanganate solution quickly at first [1] then dropwise [1]do a rough titration [1]do 2(3) accurate titrations/until concordant/60.1 cm3

until end-point/colour change [1] maximum of [6]

(b) Titration Volume at

start/cm3Volume atend/cm3

Added volume/cm3

1

2

3

Average titre 5 cm3

Clearly labelled and neatly presented table, including units and the recording of the average titre. [1]

Significant figures: All accurate titration readings recorded to one decimal place (including initial burette reading a 0.0 if used). Accept, however, 0.00 and 0.05 but penalise by [–1] if other readings are given to two or more decimal places. The use of 0 is penalised by [–1] if used (only penalise once). [2]

Titration consistency: This is the difference between the accurate readings.

Difference Mark 60.1 2 60.2 1 .0.3 0 [2]

6620.06 3

AVAILABLEMARKS

Agreement with supervisor’s average titre(The supervisor’s titration value should be recorded in red ink beside the candidates’ average titre). If average titre calculated incorrectly the correct value should be determined and used for agreement mark.

Difference Mark 60.1 3 60.2 2 60.3 1 .0.3 0 [3]

Average titre: the inclusion of the rough titre in this calculation is penalised by [–1]. The average titre can be to two decimal places e.g. 21.33.

An incorrect calculation is 0 but this error must be carried through to other calculations, if appropriate. [2]

(c) colourless to pink [2]

(d) 5Fe21 1 8H1 1 MnO42 5Fe31 1 4H2O 1 Mn21 [2]

(e) Assuming a titration figure of 20.0 cm3 and a pipette figure of 25 cm3

volume 3 molarity of ammonium iron(II) sulfate 5 5 3 volume 3 molarity permanganate

25 3 M 5 5 3 20 3 0.02 5 2 25 3 M 5 0.08 [2]

(f) 0.08 mol 5 31.4 g 1 mol 5 31.4/0.08 5 392.5 g Fe(NH4)2(SO4)2nH2O 5 56 1 2 3 18 1 2 3 96 1 18n Fe(NH4)2(SO4)2nH2O 5 284 1 18n Hence 392.5 5 284 1 18n Hence 18n 5 108.5 Hence 18n 5 6.03 Hence 18n 5 6 [3] 25


AVAILABLEMARKS

2 (a) Test Observation Deduction1 Describe the appearance of A.

pink/red/maroon crystals/solid [1]

transition metalcompound/cobaltion or compound/hydrated or water of crystallisation if crystals stated [1]

2 Add a spatula measure of A to approximately 50 cm3 of water and stir.

dissolves/soluble/disappears [1] pink [1] solution [1]Max. [2]

soluble/confirms transitionmetal compound/cobaltion or compound [1]award only once

3 Add 10 drops of silver nitrate solution to 2 cm3 of the solution of A in a test tube. Allow to stand.

white [1] precipitate [1] chloride [1]

4 Add 5 drops of sodium hydroxide solution to 2 cm3 of the solution of A in a test tube.

(dark) blue precipitate/darkens on standing [1]

insoluble hydroxide [1]Co(OH)2 etc

5 In a fume cupboard, add 6 cm3 of concentrated ammonia, slowly, to 2 cm3 of the solution of A in a test tube.

blue ppt [1](any) ppt dissolves [1]yellow solution [1]darkens/turns brown [1]Max. [3]


6 Add 4 cm3 of concentrated hydrochloric acid to 2 cm3 of the solution of A in a test tube.

goes blue [1]


A is (hydrated) cobalt chloride/cobalt(II) chloride [1]

6620.06 5

AVAILABLEMARKS

(b) Test Observation Deduction1 Describe the appearance of B.

white solid/crystals [1] high RMM/long chain/strong (intermolecular)forces named white organic solidno chromophoreglycine or alanine [1]

2 Heat one spatula measure of B in a test tube. Heat gently at first and then more strongly. Test any fumes with a glass rod dipped in concentrated hydrochloric acid.

White smoke

(smoke is) NH4Clmolecules contain N/ammonia [1]

3 (i) Dissolve 2 spatula measures of B in approximately 20 cm3 of water.

(ii) Use Universal Indicator paper to determine the pH of the solution of B.

green colour [1] pH 6/7 [1]

4 Add 6 drops of copper(II) sulfate solution, dropwise, to a test tube half-full of a solution of B.

blue colour [1] contains – NH2/– NH/glycine/any amino acid/correct comment on complex formed with amino acid [1]

5 To 3 cm3 of acidified potassium dichromate solution add one spatula measure of B and warm gently.

No change/stays orange [1]

not a primary or secondary alcohol/could be – COOH

– NH2– tert alcohol– ketone

dichromate not reduced [1]

Identity of B: glycine [1]

Maximum [25] 25


AVAILABLEMARKS

3 (a) 2 Na(l) 1 O2(g) Na2O2(s) [2]

(b) Na2O2 5 2 3 23 1 2 3 16 5 46 1 32 5 78 1.3 g 5 1 3

78. 5 0.0167 mol 1

60( ) 46 g needed for 78 46 3 0.0167 5 0.768 5 0.77 g If an 80% yield will need error [–1] 100

80 3 0.77 g 5 0.96 g [4]

(c) sodium/Na2O2 reacts with water/moisture hence less sodium to react with oxygen yield of Na2O2 reduced/NaOH or H2O2/is formed [2]

(d)

oxygen or air

U tube

sodium

heat

air or oxygen

aluminium boat

e.g.anhydrous calcium chloride

[4]

(e) (i) Na2O2 1 H3PO4 Na2HPO4 1 H2O2 [2]

(ii) The (hydrated)/salt (of Na2HPO4.12H2O) [1] removes water from the solution [1] thus concentrating the solution [1]. [2]

(f) *retention time/peak [1] compare to pure sample of oxygen [1] – *depends on 1st line [2]

6620.06 7

AVAILABLEMARKS

Quality of written communication:

2 marks The candidate expresses ideas clearly and fluently through well-linked sentences and paragraphs. Arguments are generally relevant and well-structured. There are few errors of grammar, punctuation and spelling.

1 mark The candidate expresses ideas clearly, if not always fluently. Arguments may sometimes stray from the point. There may be some errors of grammar, punctuation and spelling, but not such as to suggest a weakness in these areas.

0 marks The candidate expresses ideas satisfactorily, but without precision. Arguments may be of doubtful relevance or obscurely presented. Errors in grammar, punctuation and spelling are sufficiently intrusive to disrupt the understanding of the passage. [2]

Total

20

70

TIME

2 hours 30 minutes.




The total mark for this paper is 70.Questions 1 and 2 are practical exercises each worth 25 marks.Question 3 is a planning exercise worth 20 marks.Quality of written communication will be assessed in Questions 3(d) and (e).You may not have access to notes, textbooks and other material

to assist you.A Periodic Table of elements (including some data) is provided.

051657


2012

7563


Question Number Marks

Modera- tion Mark

1

2

3

TotalMarks

Chemistry



[AC231]

WEDNESDAY 9 MAY, MORNING

Centre Number

71

Candidate Number

AC231

TeacherMark

Examiner Check

Remark

7563 2

1 1.2 g of an impure sample of potassium iodate(V), KIO3, is to be analysed for percentage purity. A 250 cm3 solution of the sample was prepared in a volumetric flask.

(a) Describe how the 250 cm3 solution of potassium iodate(V) was prepared.

[6]


a sample of the solution of potassium iodate(V) four 10 cm3 portions of dilute sulfuric acid four 1.0 g portions of potassium iodide 0.1 mol dm23 sodium thiosulfate solution starch indicator

Assuming that all the apparatus is clean and dry, you are required to carry out a titration to determine the percentage purity of the sample of potassium iodate(V) using the method given below.

● Pipette 25.0 cm3 of the potassium iodate(V) solution into a conical flask.

● Add 10 cm3 of dilute sulfuric acid to the conical flask. ● Add 1.0 g of potassium iodide to the conical flask and swirl the

flask to ensure it dissolves. ● Titrate, using the 0.1 mol dm23 sodium thiosulfate solution, until

the solution is straw coloured. ● Add starch indicator to the conical flask and titrate until the

indicator changes from blue-black to colourless.

TeacherMark

Examiner Check

Remark

7563 3 [Turn over

(b) Carry out the titration and record your results in a suitable table in the space below. Calculate the average titre.

[10]

7563 4

TeacherMark

Examiner Check

Remark (c) (i) Write the equation for the reaction between potassium

iodate(V) and potassium iodide in the presence of dilute sulfuric acid.

[2]

(ii) Write an ionic equation for this reaction.

[1]

(d) (i) Iodine reacts with sodium thiosulfate according to the equation:

I2 1 2S O2 322 S O4 6

22 1 2I2

Calculate the mass of KIO3 in the sample.

[5]

(ii) Calculate the percentage purity of the KIO3 sample.

[1]

7563 5 [Turn over

TeacherMark

Examiner Check

Remark2 Observation/deduction


(a) You are provided with a sample of an inorganic compound labelled A.

(i) You are required to carry out the following tests on the compound and record your observations in the table.

Test Observations

1 Describe the appearance of A.[2]

2 Dissolve 3 spatula measures of A in 15 cm3 of deionised water.

Keep this solution for tests 3(a), 4, 5(a) and 6.

[1]

3 (a) Place 2 cm3 of the solution from test 2 in a test tube and add an equal volume of sodium hydroxide solution.

(b) Add a further 5 cm3 of sodium hydroxide solution to the test tube.

[3]

4 Place 2 cm3 of the solution from test 2 in a test tube and add 4 cm3 of edta solution.

[1]

5 (a) Place 2 cm3 of the solution from test 2 in a test tube and add 5 cm3 of dilute ammonia solution.

(b) Place 2 cm3 of the solution from test 5(a) in another test tube and add 2 cm3 of 1,2-diaminoethane (en) solution.

[2]

6 Place 2 cm3 of the solution from test 2 in another test tube and add 2 cm3 of barium chloride solution. Allow to stand.

[2]

7563 6

TeacherMark

Examiner Check

Remark (ii) Identify compound A.

[2]

(iii) Complex ions are formed in tests 4, 5(a) and 5(b). Suggest the formulae of the complex ions formed in these tests.

Test 4:

Test 5(a):

Test 5(b): [3]

(iv) Explain why a reaction occurs in test 5(b).

[2]

7563 7 [Turn over

TeacherMark

Examiner Check

Remark (b) You are provided with an aqueous mixture of two organic

compounds labelled Y. Both of the compounds in the mixture contain a carbonyl group.

(i) You are required to carry out the following tests on the organic mixture and record your observations in the table.

Test Observations

1 Describe the appearance of Y.Cautiously smell Y and give a description of its smell.

[2]

2 Place 3 cm3 of Y in a test tube and add 10 drops of acidified potassium dichromate solution. Warm in a water bath.

[2]

3 Place 3 cm3 of Y in another test tube and add half a spatula measure of sodium hydrogencarbonate.

[3]

(ii) State the two types of organic compounds in the mixture Y.

[2]

Maximum [25] marks

TeacherMark

Examiner Check

Remark

7563 8

3 Planning Exercise

Preparation and purification of the 2,4-dinitrophenylhydrazone derivative obtained from the reaction of methanal with 2,4-dinitrophenylhydrazine.

C�N�NH

NO2

NO2

H

H

The hydrazone, shown above, may be prepared by reacting excess aqueous 2,4-dinitrophenylhydrazine with methanal.

Methanal is gaseous at room temperature but can be obtained as a solution which contains 37% methanal, by mass.

(a) Write the equation for the formation of the 2,4-dinitrophenylhydrazone.

[2]

(b) Calculate the mass of methanal solution needed to form 1.4 g of the 2,4-dinitrophenylhydrazone assuming a 95% yield.

[4]

(c) Methanal causes severe irritation of the nasal system and affects the throat. What safety precaution needs to be carried out during the preparation?

[1]

TeacherMark

Examiner Check

Remark

7563 9 [Turn over

Quality of written communication is assessed in parts (d) and (e).

(d) The 2,4-dinitrophenylhydrazone is formed as an orange precipitate which is collected by suction filtration using a Buchner flask.

(i) Explain how “Buchner filtration” is carried out.

[3]

(ii) State why it is used in preference to normal filtration.

[2]

(e) The solvent used to recrystallise the 2,4-dinitrophenylhydrazone is ethanol.

(i) Explain why the 2,4-dinitrophenylhydrazone is soluble in ethanol and not in hexane.

[2]

(ii) Describe how you would recrystallise the 2,4-dinitrophenylhydrazone.

[4]


112041


ADVANCED SUBSIDIARY (AS)General Certificate of Education

2012

ChemistryAssessment Unit A2 3

Internal AssessmentPractical Examination 1

[AC231]


7563.01

MARKSCHEME

7563.01 22 [Turn over

AVAILABLEMARKS

Annotation

1. Please do all marking in red ink.

2. All scripts should be checked for mathematical errors. Please adopt a system of one tick () equals 1 mark, e.g. if you have awarded 4 marks for part of a question then 4 ticks () should be on this candidate’s answer.

3. The total mark for each question should be recorded in a circle placed opposite the question number in the teacher mark column.


General points

• All calculations are marked according to the number of errors made.

• Errors can be carried through. If the wrong calculation is carried out then the incorrect answer can be carried through. One mistake at the start of a question does not always mean that all marks are lost.

• Listing is when more than one answer is given for a question that only requires one answer, e.g. the precipitate from a chloride with silver nitrate is a white solid; if the candidate states a white or a cream solid, one answer is correct and one answer is wrong. Hence they cancel out.

• Although names might be in the mark scheme it is generally accepted that formulae can replace them. Formulae and names are often interchangeable in chemistry.

• The marking of colours is defined in the ‘CCEA GCE Chemistry Acceptable Colours’ document.

MARKING GUIDELINES

Interpretation of the Mark Scheme

• Carry error through This is where mistakes/wrong answers are penalised when made, but if carried

into further steps of the question, then no further penalty is applied. This pertains to calculations and observational/deduction exercises. Please annotate candidates’ answers by writing the letters c.e.t. on the appropriate place in the candidates’ answers.

• Oblique/forward slash This indicates an acceptable alternative answer(s).

• Brackets Where an answer is given in the mark scheme and is followed by a word/words in

brackets, this indicates that the information within the brackets is non-essential for awarding the mark(s).

7563.01 3 3

AVAILABLEMARKS

Section A

1 (a) Weigh 1.2 g of sample [1] Dissolve sample in (minimum) volume of deionised water with stirring [1] pour solution into (250 cm3) volumetric flask (through funnel) [1] indication of thorough rinsing of all apparatus (container, glass rod) [1] rinsings added to the volumetric flask [1] make up volume to 250 cm3 using deionised water until bottom of meniscus is on the line [1] invert/shake (to mix thoroughly) [1] To a maximum of [6] [6]

(b) Table [3] The Table should be drawn as a table. It should be labelled with the following:

initial (burette) reading, final (burette) reading and the titre. It is not necessary to use exactly these words but there should be appropriate columns and rows [1]. Units, i.e. cm3, should be stated [1].

The rough titration value should not be the same as the accurate values [1].

Use of decimal places [2] All burette readings should be to at least one decimal place – each mistake is

penalised by one mark.

(However initial burette readings of 0 are penalised once only.)

If used, the second decimal place position should be 0 or 5 only – other values will be penalised by 1 mark for each.

Average titre [2] Accurate titrations only should be used. The use of a rough value is [–1]. The average value can be calculated to two decimal places or more, e.g.

25.15 and 25.20 average to 25.175.

If three accurate titres are recorded, then the average titre must be calculated using all three accurate titres.

Any error is [–1]. This might be an incorrect calculation or the omission of units. If the average titre is included in the table then the units indicated on the table apply.

Titration consistency [1] This is the difference within the accurate titrations. If three accurate values

are given then the difference between highest and lowest is used.

Difference Mark ±0.1 [1] >0.1 [0]

Titration agreement [2] The correct average titre is used. If the incorrect average has been calculated

the correct one is calculated and used.

±0.1 [2] ±0.2 [1] >0.2 [0]

7563.01 44 [Turn over

AVAILABLEMARKS

The difference should be rounded to one decimal place. Please note that the supervisor’s titre should be recorded after the candidate’s table on their script in red ink.

The marks for table, decimal places etc. should be recorded at the candidate’s table of results. [10] (c) (i) KIO3 + 5KI + 3H2SO4 → 3I2 + 3K2SO4 + 3H2O unbalanced [–1] [2] (ii) IO3

– + 5I– + 6H+ → 3I2 + 3H2O [1]

(d) (i) moles of Na2S2O3 = 1000

average titre 0.1#

moles of I2 = moles of Na2S2O3

2

moles of KIO3 in 25.0 cm3 = moles of I2

3 moles of KIO3 in sample = moles of KIO3 in 25.0 cm3 × 10

mass of KIO3 in sample = moles of KIO3 in sample × RMM of KIO3 (214) [5]

(ii) percentage purity =

1.2mass of KIO3 100 [1] 25

error [–1] Alternative methods accepted

7563.01 5 5

AVAILABLEMARKS

2 (a) (i)

Test Observations

1 Describe the appearance of A. green [1] crystals/solid [1]accept blue-green/green-blue

2 Dissolve 3 spatula measures of A in 15cm3 of deionised water.

Keep this solution for tests 3(a), 4, 5(a) and 6.

green [1] (solution)(pale or dark green acceptable).

3 (a) Place 2cm3 of the solution from test 2 in a test tube and add an equal volume of sodium hydroxide solution.

(b) Add a further 5cm3 of sodium hydroxide solution to the test tube.

green [1] ppt [1] solid

does not dissolve [1]

4 Place 2cm3 of the solution from test 2 in another test tube and add 4cm3 of edta solution.

blue [1] solution(accept shades of blue)

5 (a) Place 2cm3 of the solution from test 2 in another test tube and add 5cm3 of dilute ammonia solution.

(b) Place 2cm3 of the solution from test 5(a) in another test tube and add 2cm3 of 1,2-diaminoethane (en) solution.

blue [1] solution

pink/purple/violet [1] solution

6 Place 2cm3 of the solution from test 2 in another test tube and add 2cm3 of barium chloride solution. Allow to stand.

white [1] ppt [1]

[11]

(ii) (hydrated) nickel [1] sulfate [1] or NiSO4 [2]

(iii) Test 4: [Ni(edta)]2– [1]

Test 5(a): [Ni(NH3)6]2+ [1]

Test 5(b): [Ni(en)3]2+ or [Ni(H2NCH2CH2NH2)3]2+ [1] [3] square brackets needed

(iv) more particles in solution/three en replace six NH3/bidentate replace monodentate [1] increase in disorder/entropy increases [1] [2]

7563.01 66 [Turn over

AVAILABLEMARKS

(b) (i)

Test Observations

1 Describe the appearance of Y. Cautiously smell Y and give a description of its smell.

colourless [1] descriptive, e.g. sharp [1] smell

2 Place 3 cm3 of Y in a test tube and add 10 drops of acidified potassium dichromate solution. Warm in a water bath.

orange [1] solutionchanges to green [1]

3 Place 3 cm3 of Y in another test tube and add half a spatula measure of sodium hydrogencarbonate.

fizzing/bubbles/effervescence [1]solid disappears [1]solution (remains) colourless [1]temperature change (down) [1]to maximum of [3]

[7]

(ii) aldehyde [1] (carboxylic) acid [1] [2]

maximum [25] 25

General:

Further observations

Candidates may record observations not recorded in the mark scheme, but credit should only be given to those observations recorded in the mark scheme.

Section A 50

7563.01 7 7

AVAILABLEMARKS

Section B

3 Planning Exercise

(a)

Molecular equation acceptable. [2]

(b) C OH

H is CH2O = 12 + 2 + 16 = 30

C NNH NO2

H

HNO2

= C7H6N4O4 = 210

210 g 2,4 DNP needs 30 g CH2O

1.4 g 210

1.4 30# = 0.2 g

37% is 0.2 g

[ need 37

100 0.2 g = 0.54 g

95% yield [ 95

100 0.54 g = 0.568 = 0.57 g [4]

(c) Fume cupboard [1]

(d) (i) place filter paper into Buchner funnel funnel placed into Buchner flask suck the air through/attached to pump [3]

(ii) Faster [1] dries crystals [1] [2]

(e) (i) Recognise that hydrazone and ethanol are both polar/hydrazone can form H-bonds with ethanol [1] Hexane is non-polar/cannot form H-bonds with hydrazone [1] [2]

(ii) Minimum volume [1] hot ethanol [1] filter [1] allow (to cool) and form crystals [1] [4] Quality of written communication [2]

C O + NH2NH C NNH NO2+ H2ONO2

H H

H HNO2

NO2

7563.01 88 [Turn over

AVAILABLEMARKS

Quality of written communication



0 marks The candidate expresses ideas satisfactorily, but without precision. Arguments may be of doubtful relevance or obscurely presented. Errors in grammar, punctuation and spelling are sufficiently intrusive to disrupt the understanding of the passage. 20

Section B 20

Total 70

TIME

2 hours 30 minutes.





to assist you.A Periodic Table of elements (including some data) is provided.

051658


2012

7564



Modera- tion Mark

1

2

3

TotalMarks

Chemistry



[AC232]

THURSDAY 10 MAY, MORNING

Centre Number

71

Candidate Number

AC232

7564 2

TeacherMark

Examiner Check

Remark1 1.2 g of an impure sample of potassium iodate(V), KIO3, is to be

analysed for percentage purity. A 250 cm3 solution of the sample was prepared in a volumetric flask.

(a) Describe how the 250 cm3 solution of potassium iodate(V) was prepared.

[6]


a sample of the solution of potassium iodate(V) four 10 cm3 portions of dilute sulfuric acid four 1.0 g portions of potassium iodide 0.1 mol dm23 sodium thiosulfate solution starch indicator

Assuming that all the apparatus is clean and dry, you are required to carry out a titration to determine the percentage purity of the sample of potassium iodate(V) using the method given below.

● Pipette 25.0 cm3 of the potassium iodate(V) solution into a conical flask.

● Add 10 cm3 of dilute sulfuric acid to the conical flask. ● Add 1.0 g of potassium iodide to the conical flask and swirl the

flask to ensure it dissolves. ● Titrate, using the 0.1 mol dm23 sodium thiosulfate solution, until

the solution is straw coloured. ● Add starch indicator to the conical flask and titrate until the

indicator changes from blue-black to colourless.

7564 3 [Turn over

TeacherMark

Examiner Check

Remark (b) Carry out the titration and record your results in a suitable table

in the space below. Calculate the average titre.

[10]

7564 4

TeacherMark

Examiner Check

Remark (c) (i) Write the equation for the reaction between potassium

iodate(V) and potassium iodide in the presence of dilute sulfuric acid.

[2]

(ii) Write an ionic equation for this reaction.

[1]

(d) (i) Iodine reacts with sodium thiosulfate according to the equation:

I2 1 2S O2 322 S O4 6

22 1 2I2

Calculate the mass of KIO3 in the sample.

[5]

(ii) Calculate the percentage purity of the KIO3 sample.

[1]

7564 5 [Turn over

TeacherMark

Examiner Check

Remark2 Observation/deduction


(a) You are provided with a sample of an inorganic compound labelled B.


Test Observations


[2]

2 Dissolve 3 spatula measures of B in 15 cm3 of deionised water.

Keep this solution for tests 3(a), 4(a), 5(a) and 6.

[1]

3 (a) Place 3 cm3 of the solution from test 2 in a test tube and add 5 drops of sodium hydroxide solution.


[3]

4 (a) In a fume cupboard place 2 cm3 of the solution from test 2 in a test tube and add 3 drops of concentrated ammonia solution.

(b) Add a further 5 cm3 of concentrated ammonia solution to the test tube.

[2]

5 (a) Place 3 cm3 of the solution from test 2 in a test tube and in a fume cupboard, add 5 cm3 of concentrated hydrochloric acid.

(b) Place 3 cm3 of the solution from test 5(a) in another test tube and add 5 cm3 of edta solution.

[2]

6 Place 3 cm3 of the solution from test 2 in another test tube and add 3 cm3 of barium chloride solution.

[2]

7564 6

TeacherMark

Examiner Check

Remark (ii) Identify compound B.

[2]

(iii) Complex ions are formed in tests 4(b), 5(a) and 5(b). Write the formulae of the complex ions formed in these tests.

Test 4(b):

Test 5(a):

Test 5(b): [3]

(iv) Explain why a reaction occurs in test 5(b).

[2]

7564 7 [Turn over

(b) You are provided with an aqueous mixture of two organic compounds labelled Z. Both of the compounds in the mixture contain a carbonyl group.

(i) You are required to carry out the following tests on the organic mixture and record your observations in the table.

Test Observations

1 Describe the appearance of Z.Cautiously smell Z and give a description of its smell.

[2]

2 Place 3 cm3 of Z in a test tube and add 10 drops of acidified potassium dichromate solution. Warm in a water bath.

[1]

3 Place 3 cm3 of Z in another test tube and add half a spatula measure of sodium hydrogencarbonate.

[3]

(ii) State the two types of organic compounds in the mixture Z.

[2]

Maximum [25] marks

TeacherMark

Examiner Check

Remark

7564 8

TeacherMark

Examiner Check

Remark3 Planning Exercise

Preparation and purification of the 2,4-dinitrophenylhydrazone derivative obtained from the reaction of butanone with 2,4-dinitrophenylhydrazine.

C�N�NH

NO2

NO2

C2H

5

CH3

The hydrazone may be prepared by reacting excess aqueous 2,4-dinitrophenylhydrazine with butanone.

Butanone is a liquid at room temperature with a density of 0.80 g cm23.

(a) Write the equation for the formation of the 2,4-dinitrophenylhydrazone.

[2]

(b) Calculate the volume of butanone needed to form 5.4 g of the 2,4-dinitrophenylhydrazone assuming a 90% yield.

[4]

(c) Butanone causes irritation of the eyes and nose. What safety precaution needs to be carried out during the preparation?

[1]

7564 9 [Turn over

TeacherMark

Examiner Check

RemarkQuality of written communication is assessed in parts (d) and (e).

(d) The 2,4-dinitrophenylhydrazone is formed as an orange precipitate which is collected by suction filtration using a Buchner flask.

(i) Explain how “Buchner filtration” is carried out.

[3]

(ii) State why it is used in preference to normal filtration.

[2]

(e) The solvent used to recrystallise the 2,4-dinitrophenylhydrazone is methanol.

(i) Explain why the 2,4-dinitrophenylhydrazone is soluble in methanol and not in octane.

[2]

(ii) Describe how you would recrystallise the 2,4-dinitrophenylhydrazone.

[4]


112043



2012

MARKSCHEME

Standardising Meeting Version

Chemistry

Assessment Unit A2 3


[AC232]


7564.01

2

AVAILABLE MARKS

7564.01

Annotation





General points






MARKING GUIDELINES


• Carry error through This is where mistakes/wrong answers are penalised when made, but if carried into further steps of the question, then no further penalty is applied. This pertains to calculations and observational/deduction exercises. Please annotate candidates’ answers by writing the letters c.e.t. on the appropriate place in the candidates’ answers.


• Brackets Where an answer is given in the mark scheme and is followed by a word/words in brackets, this indicates that the information within the brackets is non-essential for awarding the mark(s).

37564.01

AVAILABLE MARKS

Section A

1 (a) Weigh 1.2 g of sample [1] Dissolve sample in (minimum) volume of deionised water with stirring [1] pour solution into (250 cm3) volumetric flask (through funnel) [1] indication of thorough rinsing of apparatus (container, glass rod) [1] rinsings added to the volumetric flask [1] make up volume to 250 cm3 using deionised water until bottom of meniscus is on the line [1] invert/shake (to mix thoroughly) [1] To a maximum of [6] [6]

(b) Table [3] The Table should be drawn as a table. It should be labelled with the following: initial (burette) reading, final (burette) reading and the titre. It is not necessary to use exactly these words but there should be appropriate columns and rows [1]. Units, i.e. cm3, should be stated [1].

The rough titration value should not be the same as the accurate values [1].

Use of decimal places [2] All burette readings should be to at least one decimal place – each mistake is penalised by one mark.

(However initial burette readings of 0 are penalised once only.)


Average titre [2] Accurate titrations only should be used. The use of a rough value is [–1]. The average value can be calculated to two decimal places or more, e.g. 25.15 and 25.20 average to 25.175.



Titration consistency [1] This is the difference within the accurate titrations. If three accurate values are given then the difference between highest and lowest is used.


Titration agreement [2] The correct average titre is used. If the incorrect average has been calculated the correct one is calculated and used.

±0.1 [2] ±0.2 [1] >0.2 [0]

4

AVAILABLE MARKS

7564.01

The difference should be rounded to one decimal place. Please note that the supervisor’s titre should be recorded after the candidate’s table on their script in red ink.

The marks for table, decimal places etc. should be recorded at the candidate’s table of results. (c) (i) KIO3 + 5KI + 3H2SO4 → 3I2 + 3K2SO4 + 3H2O unbalanced [–1] [2] (ii) IO3 + 5I– + 6H+ → 3I2 + 3H2O [1]

(d) (i) moles of Na2S2O3 = average titre 0.1

1000 moles of I2 =

moles of Na2S2O32

moles of KIO3 in 25.0 cm3 = moles of I2

3 moles of KIO3 in sample = moles of KIO3 in 25.0 cm3 × 10

mass of KIO3 in sample = moles of KIO3 in sample × RMM of KIO3 (214) [5]

(ii) percentage purity = mass of KIO31.2 100 [1]

error [–1] Alternative methods accepted 25

57564.01

AVAILABLE MARKS

2 (a) You are provided with a sample of an inorganic compound labelled B.


Test Observations

1 Describe the appearance of B. brown/red/pink [1]solid/crystals [1]

[2]

2 Dissolve 3 spatula measures of B in 15 cm3 of deionised water.

Keep this solution for tests 3(a), 4(a), 5(a) and 6.

red/pink [1] solution

[1]

3 (a) Place 3 cm3 of the solution from test 2 in a test tube and add 5 drops of sodium hydroxide solution.


blue [1] ppt [1] solid

does not dissolve [1][3]

4 (a) In a fume cupboard place 2 cm3 of the solution from test 2 in a test tube and add 3 drops of concentrated ammonia solution.


(blue) ppt [1]

brown/yellow solution [1](accept shades) [2]

5 (a) Place 3 cm3 of the solution from test 2 in a test tube and add 5 cm3 of concentrated hydrochloric acid.

(b) Place 3 cm3 of the solution from test 5(a) in another test tube and add 5 cm3 of edta solution.

blue solution [1]accept purple/violetsolution

pink [1] solution

[2]

6 Place 3 cm3 of the solution from test 2 in another test tube and add 3 cm3 of barium chloride solution.

white [1] ppt [1]

[2] [12] (ii) (hydrated) cobalt [1] sulfate [1] or CoSO4 [2]

(iii) Test 4(b): [Co(NH3)6]2+ Test 5(a): [CoCl4]2– Test 5(b): [Co(edta)]2– [3] square brackets needed

(iv) more particles in solution/one edta replaces four Cl–/hexadentate replaces monodentate [1]

increase in disorder/entropy increases [1] [2]

6

AVAILABLE MARKS

7564.01

`(b) (i)

Test Observations

1 Describe the appearance of Z. Cautiously smell Z and give a description of its smell.

colourless [1] solution descriptive, e.g. sharp [1] smell

[2]

2 Place 3 cm3 of Z in a test tube and add 10 drops of acidified potassium dichromate solution. Warm in a water bath.

remains orange [1]

[1]

3 Place 3 cm3 of Z in another test tube and add half a spatula measure of sodium hydrogencarbonate.

fizzing/bubbles/effervescence [1]solid disappears [1]solution (remains) colourless [1]temperature change (down) [1]to maximum of [3]

[3] [6]

(ii) ketone [1]/ester/amide (carboxylic) acid [1] [2]

Maximum [25] 25

General:



Section A 50

77564.01

AVAILABLE MARKS

Section B

3 Planning Exercise

(a)

Molecular equation acceptable [2]

(b) C O C2H5

CH3

is C4H8O = 48 + 8 + 16 = 72

252 g 2,4 DNP needs 72 g butanone

5.4 g 5.4 × 72252

= 1.54 g

d = m/v 0.80 = 1.54/v

v = 1.54/0.80 = 1.93 cm3 [4]

further step for 90% yield – 2.14 cm3

(c) Fume cupboard [1]

(d) (i) funnel placed into Buchner flask place filter paper into Buchner funnel suck the air through/attached to pump maximum [3]

(ii) Faster [1] drier [1] [2]

(e) (i) Recognise that hydrazone and methanol are both polar/hydrazone can form H-bonds with methanol [1] octane is non-polar/cannot form H-bonds with hydrazone [1] [2]

(ii) Minimum volume [1] hot methanol [1] filter [1] allow (to cool) and form crystals [1] [4]


C NNH NO2

C2H5

CH3

NO2

= C10H12N4O4 = 120 + 12 + 56 + 64 = 252

C O + NH2NH C NNH NO2 NO2

C2H5C2H5

CH3CH3

NO2 NO2

+ H2O

8

AVAILABLE MARKS

7564.01

Quality of written communication



0 marks The candidate expresses ideas satisfactorily, but without precision. Arguments may be of doubtful relevance or obscurely presented. Errors in grammar, punctuation and spelling are sufficiently intrusive to disrupt the understanding of the passage. 20

Section B 20

Total 70

TIME

2 hours 30 minutes.





to assist you.A Periodic Table of the Elements, containing some data, is included in this question paper.

061274


2013

8190



Modera- tion Mark

1

2

3

TotalMarks

Chemistry



[AC231]


Centre Number

71

Candidate Number

AC231

8190 2

TeacherMark

Examiner Check

Remark1 Titration exercise

Hardness in water may be caused by the presence of dissolved calcium ions.


A solution of edta of concentration 0.01 mol dm23

A sample of hard water Four portions of pH10 buffer solution Eriochrome Black T indicator solution (use four drops) A sample solution showing the colour at the end point

Assuming that all apparatus is clean and dry, you are required to carry out a titration and use your results to determine the concentration of calcium ions in the hard water sample.

(a) Give details of the procedure you intend to use. The edta solution should go into the burette.

[6]

TeacherMark

Examiner Check

Remark

8190 3 [Turn over

(b) Carry out your procedure. Present your results in a suitable table and calculate the average titre.

[8]

(c) State the colour change at the end point of the titration.

From to [2]

TeacherMark

Examiner Check

Remark

8190 4

(d) With reference to the following equation explain the reason for adding the pH10 buffer to the reaction mixture.

Ca21 1 H2(edta)22 [Ca(edta)]22 1 2H1

[2]

(e) Calculate the concentration of the calcium ions in the hard water in mg dm23.

[5]

(f) Name another test that would be used to confirm the presence of calcium ions in the hard water, stating the expected result.

[2]

TeacherMark

Examiner Check

Remark

8190 5 [Turn over

2 Observation/deduction

Safety glasses must be worn at all times and care should be exercised during this practical examination.

(a) You are provided with a salt, labelled X. Carry out the following tests. Record your observations and deductions in the spaces below.

Test Observations Deductions

1 Describe the appearance of X.

[1] [1]

2 Add a spatula measure of X to 50 cm3 of deionised water and stir until there is no further change.

[1] [1]

3 Add 5 drops of silver nitrate solution to a test tube containing 2 cm3 of the solution of X. Allow the mixture to stand.

[3] [1]

4 Put 2 cm3 of the solution of X into a test tube.

(a) Add 5 drops of sodium hydroxide solution.

(b) Add a further 5 cm3 of sodium hydroxide solution.

[3] [3]

5 Place a spatula measure of solid X in a dry boiling tube and heat gently.

[2] [1]

Give the name of compound X

[2]

TeacherMark

Examiner Check

Remark

8190 6

(b) You are provided with an organic liquid containing one functional group, labelled Y. Carry out the following tests and record your observations and deductions in the spaces below. The mass spectrum of Y is also provided.


1 Place 2 cm3 of Y into a boiling tube. Place in a test tube rack.

(a) Under supervision, cautiously add a very small measure of phosphorus(V) chloride in a fume cupboard.

(b) In a fume cupboard, hold the stopper of a bottle of concentrated ammonia solution over the boiling tube used in test 1(a).

[2]

[1]

[1]

[1]

2 Place 2 cm3 of Y into a test tube. Add 1 cm3 of sodium carbonate solution.

[1] [1]

(i) What homologous series does Y belong to?

[1]

TeacherMark

Examiner Check

Remark

8190 7 [Turn over

Use the following mass spectrum to deduce the structure of Y.

10 15 20 25 30 35 40 45 50 55 60 65 70 75

100

80

60

40

20

0

m/z

rela

tive

abun

danc

e

(ii) Draw the structure of Y below.

[1]

Maximum [25] marks

TeacherMark

Examiner Check

Remark

8190 8

3 Planning exercise

Preparation of urea

Urea, (NH2)2CO, was first synthesised by Friedrich Wöhler in 1828. Today some seven million tons of urea are produced per year mainly for use as a fertiliser.

Urea can be prepared in the laboratory by reacting lead(II) cyanate, Pb(CNO)2, with ammonia and water to produce lead(II) hydroxide and ammonium cyanate, NH4CNO. The ammonium cyanate then rearranges when heated to form urea, which has a melting point of 133 °C.

O

C

H2N NH2

urea

(a) Write an equation for the reaction of lead(II) cyanate with ammonia and water.

[2]

(b) Assuming a 70% yield, calculate the mass of lead(II) cyanate required to produce 450 g of ammonium cyanate.

[4]

TeacherMark

Examiner Check

Remark

8190 9 [Turn over

(c) The ammonium cyanate rearranges to form urea as shown in the equation below.

NH4CNO (NH2)2CO

(i) The crude product is purified by dissolving in the minimum volume of hot ethanol, filtering to remove insoluble impurities, and cooling. What name is given to this purification process?

[1]

(ii) What practical considerations determine the choice of solvent used?

[2]

(iii) Why is the minimum amount of hot ethanol used?

[1]

(iv) How is the pure dry product obtained from the filtrate?

[2]

Quality of written communication will be assessed in parts (d) and (e).

(d) Giving practical details, describe how you would determine whether or not the crystals of urea produced are pure.

[3]

TeacherMark

Examiner Check

Remark

8190 10

(e) How could you use the following infrared spectroscopic data to follow the progress of the rearrangement of ammonium cyanate to urea?

Bond Wave number/cm21

C O 1650

C N 2100

N–H (in amines) 3200–3500

[3]



113041



2013

8190.01 F

MARKSCHEME



[AC231]


8190.01 F 22 [Turn over

AVAILABLEMARKS

Annotation





General points



• Any number of decimal places may be used provided the ‘rounding’ is correct.




MARKING GUIDELINES







8190.01 F 3 3

AVAILABLEMARKS

1 Titration exercise

(a) Rinse out a pipette with the hard water and transfer 25.0 cm3 of the hard water into a (conical) flask [1] Add a portion of pH10 buffer solution [1] Add 4 drops of Eriochrome Black T to the conical flask and swirl [1] Rinse out the burette with the edta solution and fill the burette [1] Titrate with/add the edta solution from the burette until colour matches reference sample [1] Rough and two/three accurate titrations [1] [6]

(b) Table [3] The Table should be drawn as a table. It should be labelled with the following:

initial burette reading, final burette reading and the titre. It is not necessary to use exactly these words but there should be appropriate columns and rows.

The recorded readings should be checked for mathematical accuracy [1]. The rough titration value should be greater than the accurate values (no more

than 2 cm3) [1]. Units, i.e. cm3, should be stated [1]. Use of decimal places [2] All burette readings should be to at least one decimal place – each mistake is

penalised by one mark. (However initial burette readings of 0 are penalised once only.)


Average titre [2] Accurate titrations only should be used. The use of a rough value is [–1]. The average value can be calculated to two decimal places or more, e.g. 25.15 and 25.20 average to 25.175. If three accurate titres are recorded, then the average titre must be calculated

using all three accurate titres.


Titration consistency [1] This is the difference within the accurate titrations. If three accurate values are

given then the difference between highest and lowest is used.


(c) red [1] to blue [1] [2]

(d) to remove H+ [1] and prevent reverse of equilibrium [1] [2]

8190.01 F 44 [Turn over

AVAILABLEMARKS

(e) assuming an average titre of 22.8 cm3 moles edta = (22.8 × 0.01)/1000 = 2.28 × 10–4

moles Ca2+ = 2.28 × 10–4

concentration of Ca2+ = (2.28 × 10–4 × 1000)/25 = 9.12 × 10–3 mol dm–3

mass Ca2+ = 9.12 × 10–3 × 40 = 0.3648 g concentration of Ca2+ = 364.8 (mg dm–3) [–1] each error [5]

Consequential marking/carry error through (cet) to be applied in calculations. (f) flame test [1] brick red colour [1] [2] 25

8190.01 F 5 5

AVAILABLEMARKS


There are 28 scoring points available in Question 2. However the maximum mark for this question is 25.

Please see additional notes at the end of Question 2.

If the candidate scores more than 25 then MAX 25 should be written at beginning of question in the teacher mark column.

(a)


1 Describe the appearance of X.

green solid [1] Transition metal compound or ion [1]

2 Add a spatula measure of X to 50 cm3 of deionised water and stir until there is no further change. green solution [1]

Cr 3+/Fe2+/Ni2+ [1]

3 Add 5 drops of silver nitrate solution to a test tube containing 2 cm3 of the solution of X. Allow the matrix to stand.

white [1] ppt [1]in green solution [1] chloride ion present [1]

4 Put 2 cm3 of the solution of X into a test tube.

(a) Add 5 drops of sodium hydroxide solution.


green-blue [1] ppt [1]

ppt dissolves/(green) solution [1]

insoluble hydroxide [1]

Cr 3+/Cr(OH)3 / Cr(OH)3 (H2O)3 [1]

amphoteric [1]

5 Place a spatula measure of solid X in a dry boiling tube and heat gently.

colourless liquidon sides of tube [1]

crystals change colour [1]

hydrated/water of crystallisation present [1]

Give the name of compound X. hydrated [1] chromium(lll) chloride [1] [2]

8190.01 F 66 [Turn over

AVAILABLEMARKS

(b)


1 Place 2 cm3 of Y into a boiling tube. Place in a test

tube rack.

(a) Under supervision, cautiously add a very small measure of phosphorus (V) chloride in a fume cupboard.

(b) In a fume cupboard, hold the stopper of a bottle of concentrated ammonia solution over the test tube used in test (a).

steamy fumes [1]effervescence [1]

white smoke [1]

–OH group present [1]

HCI [1]

2 Place 2 cm3 of Y into a test tube. Add 1 cm3 of sodium carbonate solution. fizz/effervescence [1] Y is acidic [1]

(i) What homologous series does Y belong to? carboxylic acids [1]

(ii) Structure of Y O

OH

C C

H

H

H C

H

H

[1] Max 25

8190.01 F 7 7

AVAILABLEMARKS

General:

An incorrect deduction can be carried through to naming the salt. A deduction based on an incorrect observation can be credited on the basis of cet.

Wrong placing of answers

In the observation/deduction question candidates may write their answers in the wrong column. This is not the penalised, e.g. a deduction written in the observation column may be credited, if correct.



Question 2 (a)

Test 1 Crystals is acceptable but not powder. Dark green is acceptable. “Transition metal ion/compound” is OK. “Transition metal” is wrong. At this point the word ‘possibly’ or similar should be used if stating possible ions. At least two out of Cr3+, Fe2+, Ni2+ must be mentioned. Ions must either be given their correct symbol and charge or be referred to as an ion (e.g. “Cr3+” or “chromium ions” are acceptable; “Cr” or “chromium” are not acceptable).

Test 2 Again at least two ions should be mentioned. Candidates can score here for the same deduction made in Test 1. No mark is awarded for deducing that X is soluble as it is referred to as a “solution” in later tests.

Test 3 When allowed to stand a white precipitate will settle at the bottom of the test tube. No other colour is acceptable. “Chloride” or “chloride ion” or “CI–” are acceptable. “Chlorine” or “CI” are not acceptable.

Test 4(a) The list of acceptable colours states that the precipitate formed, Cr(OH)3,is green-blue. However the precipitate could legitimately be observed as being pale blue, or grey-blue and these are also acceptable.

Test 5 The most important observation is the formation of the colourless liquid on the walls of the boiling tube indicating the presence of water of crystallisation, but since the crystals do change colour then this is also accepted. The actual colour is not important. If the only observation is the colour change of the crystals the candidate cannot score a mark for deduction.

Name of X The oxidation state (III) is not necessary but if an incorrect oxidation state is given then a mark is lost.

Question 2 (b)

Test 1(b) The observation could also be described as white fumes.

8190.01 F 88 [Turn over

AVAILABLEMARKS

3 Planning Exercise

(a) Pb(CNO)2 + 2NH3 + 2H2O → Pb(OH)2 + 2NH4CNO [2] (b) moles NH4CNO = 450/60 = 7.5 70% →100% (7.5/70) × 100 = 10.7 (1:2) moles Pb(CNO)2 = 10.7/2 = 5.35 mass Pb(CNO)2 = 5.35 × 291 = 1557 g [4]

(c) (i) recrystallisation [1] (ii) desired product soluble in hot solvent [1] but insoluble when solvent is

cold [1]/other impurities remain in solution when cold [1] [2]

(iii) prevents loss of product [1]

(iv) filter [1] dry in low temperature oven/desiccator [1] [2]

(d) sample in capillary tube sealed at one end [1] heat slowly [1] (in oil bath) sharp melting point at 133 °C indicates purity [1] [3]

(e) peak at 2100 cm–1 diminished [1] peaks form at 1650 cm–1 [1] and 3200–3500 cm–1 [1] [3] Quality of written communication marked in Questions 3 (d) and (e) [2] 20

Total 70

TIME

2 hours 30 minutes.




The total mark for this paper is 70.Questions 1 and 2 are practical exercises each worth 25 marks.Question 3 is a planning exercise worth 20 marks.Quality of written communication will be assessed in Question 3(f).You may not have access to notes, textbooks and other materialto assist you.

A Periodic Table of the Elements, containing some data, is included in this question paper.

061275


2013

8191



Modera- tion Mark

1

2

3

TotalMarks

Chemistry



[AC232]


Centre Number

71

Candidate Number

AC232

8191 2

TeacherMark

Examiner Check

Remark1 Titration exercise

Hardness in water may be caused by the presence of dissolved magnesium ions.


A solution of edta of concentration 0.02 mol dm23

A sample of hard water Four portions of pH 10 buffer solution Eriochrome Black T indicator solution (use four drops) A sample solution showing the colour at the end point

Assuming that all apparatus is clean and dry, you are required to carry out a titration and use your results to determine the concentration of magnesium ions in the hard water sample.

(a) Give details of the procedure you intend to use. The edta solution should go into the burette.

[6]

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8191 3 [Turn over

(b) Carry out your procedure. Present your results in a suitable table and calculate the average titre.

[8]

(c) State the colour change at the end point of the titration.

From to [2]

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8191 4

(d) With reference to the following equation explain the reason for adding the pH10 buffer to the reaction mixture.

Mg21 1 H2(edta)22 [Mg(edta)]22 1 2H1

[2]

(e) Calculate the concentration of the magnesium ions in the hard water in mg dm23.

[5]

(f) A solution of magnesium ions can be used to distinguish between solutions of carbonate and hydrogencarbonate ions. State the expected observations.

[2]

TeacherMark

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8191 5 [Turn over



(a) You are provided with a salt, labelled R. Carry out the following tests. Record your observations and deductions in the spaces below.


1 Describe the appearance of R.

[1] [1]

2 Add a spatula measure of R to 50 cm3 of deionised water and stir until there is no further change.

[1] [1]

3 Add 5 drops of silver nitrate solution to a test tube containing 2 cm3 of the solution of R. Allow the mixture to stand.

[3] [1]

4 Put 2 cm3 of the solution of R into a test tube.

(a) Add 5 drops of sodium hydroxide solution and allow to stand.


[4] [2]

5 Place a spatula measure of solid R in a dry boiling tube and heat gently.

[2] [1]

Give the name of compound R

[2]

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8191 6

(b) You are provided with an organic liquid containing one functional group, labelled S. Carry out the following tests and record your observations and deductions in the spaces below. The mass spectrum of S is also provided.


1 Place 2 cm3 of S into a boiling tube. Place in a test tube rack.

(a) Under supervision, cautiously add a very small measure of phosphorus(V) chloride in a fume cupboard.


[2]

[1]

[1]

[1]

2 Place 2 cm3 of S into a test tube. Add 1 cm3 of sodium carbonate solution.

[1] [1]

(i) What homologous series does S belong to?

[1]

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8191 7 [Turn over

Use the following mass spectrum to deduce the structure of S.

10 15 20 25 30 35 40 45 50 55 60 65 70 75

100

80

60

40

20

0

m/z

rela

tive

abun

danc

e

(ii) Draw the structure of S below.

[1]

Maximum [25] marks

TeacherMark

Examiner Check

Remark

8191 8

3 Planning exercise

Preparation of aspirin

Aspirin can be prepared by reacting 2-hydroxybenzoic acid with ethanoic anhydride in the presence of concentrated phosphoric(V) acid. The product has a melting point of 135 °C.

COOH

OH

� (CH3CO)

2O

COOH

O — C — CH3

O

� CH3COOH

The following method can be used:

Place 20.0 g of 2-hydroxybenzoic acid in a pear-shaped flask and add 40 cm3 of ethanoic anhydride. Safely add 5 cm3 of concentrated phosphoric(V) acid to the mixture. Heat under reflux. Add water to hydrolyse any unreacted ethanoic anhydride to form ethanoic acid. Pour the mixture onto 400 g of crushed ice in a beaker. The product is removed by suction filtration, recrystallised from water and dried in a desiccator. The melting point is then determined.

(a) (i) Suggest the role of the concentrated phosphoric(V) acid.

[1]

(ii) Explain how you would safely add the concentrated phosphoric(V) acid.

[2]

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8191 9 [Turn over

(b) (i) What is meant by the term reflux?

[1]

(ii) Draw a labelled diagram showing the apparatus used for refluxing.

[3]

(c) Write an equation for the hydrolysis of ethanoic anhydride.

[2]

(d) Why is the mixture poured onto ice?

[1]

(e) Why is suction filtration used rather than gravity filtration?

[1]

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8191 10

(f) Describe how the impure product is recrystallised.

[3]


(g) Assuming a 65% yield, calculate the mass of 2-hydroxybenzoic acid required to form 5.0 g of pure aspirin.

[4]


113043


MARKSCHEME


8191.01 F


2013



[AC232]


2

AVAILABLE MARKS

8191.01 F

Annotation





General points







MARKING GUIDELINES





3

AVAILABLE MARKS

8191.01 F


(a) Rinse out a pipette with the hard water and transfer 25.0 cm3 of the hard water into a (conical) flask [1] Add a portion of pH10 buffer solution [1] Add 4 drops of Eriochrome Black T to the conical flask and swirl [1] Rinse out the burette with the edta solution and fill the burette [1] Titrate with/add the edta solution from the burette until colour matches reference sample [1] Rough and two/three accurate titrations [1]

To a maximum of [6] [6]

(b) Table [3] The Table should be drawn as a table. It should be labelled with the following: initial burette reading, final burette reading and the titre. It is not necessary to use exactly these words but there should be appropriate columns and rows. The recorded readings should be checked for mathematical accuracy. [1].

The rough titration value should be greater than the accurate values (no more than 2 cm3) [1].

Units, i.e. cm3, should be stated [1].

Use of decimal places [2] All burette readings should be to at least one decimal place – each mistake is penalised by one mark. (However initial burette readings of 0 are penalised once only.)


Average titre [2] Accurate titrations only should be used. The use of a rough value is [–1]. The average value can be calculated to two decimal places or more, e.g. 25.15 and 25.20 average to 25.175. If three accurate titres are recorded, then the average titre must be calculated using all three accurate titres.


Titration consistency [1] This is the difference within the accurate titrations. If three accurate values are given then the difference between highest and lowest is used.

Difference Mark ±0.1 [1] >0.1 [0] [8]

4

AVAILABLE MARKS

8191.01 F

(c) red [1] to blue [1] [2]

(d) to remove H+ [1] and prevent reverse of equilibrium [1] [2]

(e) assuming an average titre of 22.8 cm3

moles edta = (22.8 × 0.02)/1000 = 4.56 × 10–4

moles Mg2+ = 4.56 × 10–4 concentration of Mg2+ = (4.56 × 10–4 × 1000)/25 = 0.0182 mol dm–3

mass Mg2+ = 0.018 × 24 = 0.437 g concentration of Mg2+ = 437 mg dm–3 [–1] each error [5]

Consequential marking/carry error through (cet) to be applied in calculations.

(f) carbonate – white precipitate [1] hydrogencarbonate – no precipitate/solution remains colourless [1] [2] 25

5

AVAILABLE MARKS

8191.01 F


There are 28 scoring points available in Question 2. However the maximum mark for this question is 25. Please see additional notes at the end of Question 2.

If the candidate scores more than 25 then MAX 25 should be written at beginning of question in the teacher mark column.

(a)


1 Describe the appearance of R. pink [1] solid

Transition metal compound or ion [1]

2 Add a spatula measure of R to approximately 50 cm3 of deionised water and stir until there is no further change.

colourless/pale pink solution [1] Mn2+/Co2+ [1]

3 Add 5 drops of silver nitrate solution to a test tube containing 2 cm3 of the solution of R. Allow the mixture to stand.

white [1] ppt [1]in pale pink/colourless solution [1] chloride ion present [1]

4 Put 2 cm3 of the solution of R into a test tube.

(a) Add 5 drops of sodium hydroxide solution and allow to stand.


white [1] ppt [1] turns brown/black/darkens [1]

ppt remains [1]

insoluble hydroxide [1]

Mn2+/Mn(OH)2 / Mn(OH)2 (H2O)4 [1]

5 Place a spatula measure of solid R in a dry boiling tube and heat gently.

colourless liquidon sides of tube [1]crystals changecolour [1]

hydrated/water of crystallisation present [1]

Give the name of compound R

hydrated [1] manganese(ll) chloride [1] [2]

6

AVAILABLE MARKS

8191.01 F

(b)


1 Place 2 cm3 of S into a boiling tube. Place in a test

tube rack.

(a) Under supervision, cautiously add a very small measure of phosphorus(V) chloride, in a fume cupboard.


steamy fumes [1]effervescence [1]

white smoke [1]

–OH group present [1]

HCI [1]

2 Place 2 cm3 of S into a test tube. Add 1 cm3 of sodium carbonate solution. fizz/effervescence [1] S is acidic [1]

(i) What homologous series does S belong to?

carboxylic acids [1]

(ii) Structure of S

HO

OH

C C

H

H

[1] Max 25

7

AVAILABLE MARKS

8191.01 F

General:

An incorrect deduction can be carried through to naming the salt. A deduction based on an incorrect observation can be credited on the basis of c.e.t.

Wrong placing of answers

In the observation/deduction question candidates may write their answers in the wrong column. This is not penalised, e.g. a deduction written in the observation column may be credited, if correct.



Question 2 (a)

Test 1 Crystals is acceptable but not powder. “Transition metal ion/compound” is OK. “Transition metal” is wrong. At this point the word ‘possibly’ or similar should be used if stating possible ions. Both Mn2+ and Co2+ are pink but since Mn2+ is a much paler shade of pink it would be acceptable at this point to suggest that Mn2+ is possibly present without mention of Co2+. Ions must either be given their correct symbol and charge or be referred to as an ion (e.g. “Mn2+” or “manganese ions” are acceptable; “Mn” or “manganese” are not acceptable).

Test 2 The solution is an extremely pale pink colour so “colourless” is also acceptable.Candidates can score here for the same deduction made in Test 1. No mark is awarded for deducing that R is soluble as it is referred to as a “solution” in later tests.

Test 3 When allowed to stand a white precipitate will settle at the bottom of the test tube. No other colour is acceptable. “Chloride” or “chloride ion” or “Cl–” are acceptable. “Chlorine” or “CI” are not acceptable.

Test 4(a) The list of acceptable colours states that the precipitate formed, Mn(OH)2,is white. However, since it darkens so quickly, the precipitate could legitimately be observed as being cream or beige and these are also acceptable. The list of acceptable colours states that the precipitate turns brown/black on standing but it is acceptable to observe that the precipitate “darkens”.

Test 5 The most important observation is the formation of the colourless liquid on the walls of the boiling tube indicating the presence of water of crystallisation, but since the crystals do change colour then this is also accepted. The actual colour is not important. If the only observation is the colour change of the crystals the candidate cannot score a mark for deduction.

Name of R The oxidation state (II) is not necessary but if an incorrect oxidation state is given then a mark is lost.

Question 2 (b)

Test 1(b) The observation could also be described as white fumes.

8

AVAILABLE MARKS

8191.01 F

3 Planning Exercise

(a) (i) catalyst [1]

(ii) slowly/dropwise [1] gloves [1] [2] (b) (i) repeated boiling and condensing of a reaction mixture [1]

(ii)

heat

reaction mixture

water in

water out condenser

no heat source [–1] no double jacket on condenser [–1] condenser sealed at top [–1] top of flask open [–1] no labels [–1] [3]

(c) (CH3CO)2O + H2O → 2 CH3COOH [2]

(d) to form crystals/solid/product [1]

(e) faster/gives drier product [1]

(f) dissolve in minimum volume of hot water [1] filter [1] cool [1] [3] Quality of written communication [2]

(g) number of moles aspirin = 5 ÷ 180 = 0.028 0.0278 ÷ 65 × 100 = 0.043 number of moles 2-hydroxybenzoic acid = 0.043 mass 2-hydroxybenzoic acid = 0.043 × 138 = 5.9 g [4] 20

Total 70

TIME2 hours 30 minutes.

INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all three questions.Write your answers in the spaces provided.

INFORMATION FOR CANDIDATESThe total mark for this paper is 70.Questions 1 and 2 are practical exercises each worth 25 marks.Question 3 is a planning exercise worth 20 marks.Quality of written communication will be assessed in Question 3(b).You may not have access to notes, textbooks and other material to assist you.A Periodic Table of the Elements, containing some data, is included in this question paper.

ADVANCEDGeneral Certifi cate of Education

2014

8812

Chemistry



[AC231]


Centre Number

71

Candidate Number

AC231


QuestionNumber

Examiner Mark Remark

123

TotalMarks

8812 2

Examiner Only Marks Remark


You are required to dissolve a weighed sample of ammonium iron(II) sulfate in dilute sulfuric acid and make the solution up to 250 cm3 in a volumetric flask. You will then titrate 25.0 cm3 portions of this solution with acidified potassium manganate(VII). You will then use your results to calculate the concentration of the acidified potassium manganate(VII) solution.


• Hydrated ammonium iron(II) sulfate, (NH4)2Fe(SO4)2.6H2O • Dilute sulfuric acid • Deionised water • A 250 cm3 volumetric flask • An acidified solution of potassium manganate(VII).

(a) (i) Weigh out between 7.80 g and 7.90 g of ammonium iron(II) sulfate. Record the mass to two decimal places.

Mass of (NH4)2Fe(SO4)2.6H2O [2]

(ii) Dissolve the weighed sample in approximately 100 cm3 of dilute sulfuric acid and make the solution up to 250 cm3 in the volumetric flask using deionised water. Calculate the concentration of the solution in mol dm–3.

[3]

8812 3 [Turn over


(b) Titrate 25.0 cm3 portions of your solution with acidified potassium manganate(VII). Record your results in a suitable table in the space below. Calculate the average titre.

[8]

(c) (i) Describe how you ensured the end point of your titration was accurate.

[2]

(ii) State the colour change at the end point of your titration.

[1]

8812 4


(d) (i) Write the half-equation for the reduction of acidified manganate(VII) ions to form manganese(II) ions.

[2]

(ii) Write the half-equation for the oxidation of iron(II) ions to iron(III) ions.

[1]

(iii) Write the ionic equation for the reaction.

[2]

(iv) Calculate the concentration of the acidified potassium manganate(VII) solution in g dm–3.

[4]

8812 5 [Turn over

BLANK PAGE

(Questions continue overleaf)

8812 6




(a) (i) You are provided with a solid, labelled A. Carry out the following tests. Record your observations in the spaces below.

(ii) Identify A.

[2]

Test Observations

1 Describe the appearance of A.

[1]

2 Dissolve two spatula measures of A in approximately 50 cm3 of water.

Keep this solution for use in further tests.

[1]

3 Place 4 cm3 of the solution from test 2 in a test tube.

Add an equal volume of concentrated hydrochloric acid.

[1]


Add an equal volume of 1,2-diaminoethane solution. [1]

5 (a) Place 4 cm3 of the solution from test 2 in a test tube. Slowly add an equal volume of sodium hydroxide solution.

(b) Add a further 5 cm3 of sodium hydroxide solution. [2]

6 Place 4 cm3 of the solution from test 2 in a test tube. In a fume cupboard, add an equal volume of concentrated ammonia solution.

[1]

7 Place 4 cm3 of the solution from test 2 in a test tube. Add 1 cm3 of barium chloride solution dropwise.

[1]

8812 7 [Turn over


(iii) Suggest the formulae of the complex ions formed in tests 2, 3, 4 and 6.

Test 2 ___________________________________________ [1]

Test 3 ___________________________________________ [1]

Test 4 ___________________________________________ [1]

Test 6 ___________________________________________ [1]

(iv) Give the formulae of the precipitates formed in tests 5 and 7.

Test 5 ___________________________________________ [1]

Test 7 ___________________________________________ [1]

8812 8


(b) (i) You are provided with an aqueous solution of an organic compound B. Carry out the following tests. Record your observations in the spaces below.

(ii) Identify the functional group present in B.

[1]

(iii) Suggest how the infrared spectrum of B could confirm the presence of this functional group.

[2]

(iv) Suggest how the mass spectrum of B could confirm its identity.

[2]

Test Observations

1 Describe the solution. Include a description of its smell.

[1]

2 Place 4 cm3 of the solution in a test tube. Add an equal volume of potassium dichromate solution and acidify with 1 cm3 of dilute sulfuric acid. Heat in a water bath for five minutes.

[1]

3 Place 4 cm3 of the solution in a test tube. Add half a spatula measure of sodium hydrogencarbonate.

[2]

8812 9 [Turn over

BLANK PAGE

(Questions continue overleaf)

8812 10


3 Planning exercise

Ethyl methanoate, HCOOCH2CH3, exists as a liquid at room temperature and pressure. Its boiling point is 55 °C and its density is 0.9 g cm–3.

(a) (i) Write the equation for the formation of ethyl methanoate from methanoic acid and ethanol.

[1]

(ii) Assuming a 60% yield, calculate the minimum mass of each reactant required to produce 4.44 g of ethyl methanoate.

[3]

(b) Describe the laboratory preparation of ethyl methanoate up to and including the removal of the crude product from the reaction mixture.

[5]


8812 11


(c) The crude product can be purified using an aqueous solution of sodium carbonate followed by anhydrous calcium chloride.

(i) Why and how is the sodium carbonate solution used?

[4]

(ii) Why and how is the anhydrous calcium chloride used?

[2]

8 [Turn over

8812 12


(d) Part of the nmr spectrum of ethyl methanoate is shown below. Complete the nmr spectrum in terms of integration and splitting pattern.

[3]

9 8 7 6 5 4 3 2 1 0

ppm

8812

Permission to reproduce all copyright material has been applied for.In some cases, efforts to contact copyright holders may have been unsuccessful and CCEAwill be happy to rectify any omissions of acknowledgement in future if notifi ed.


2014

Chemistry


Practical Examinations 1 and 2[AC231] [AC232]

THURSDAY 15 MAY AND FRIDAY 16 MAY

8812.02

APPARATUSAND

MATERIALSLIST

*AC231**AC232*

AC

231

AC

232

8812.02 22 [Turn over

Advice for centres

● All chemicals used should be at least laboratory reagent specification and labelled with appropriate safety symbols, e.g. irritant.

● For centres running multiple sessions – candidates for the later session should be supplied with clean, dry glassware. If it is not feasible then glassware from the first session should be thoroughly washed, rinsed with deionised water and allowed to drain.

● Ensure all chemicals are in date otherwise expected observations may not be seen.

8812.02 3 3


Each candidate must be supplied with safety goggles or glasses.

Question 1

Each candidate must be supplied with:

• one 50 cm3 burette of at least class B quality

• one 25 cm3 pipette of at least class B quality

• one 250 cm3 volumetric fl ask

• a safety pipette fi ller

• three conical fl ask of 250 cm3 capacity

• a funnel for fi lling the burette (optional)

• a white tile or white paper

• 250 cm3 beaker

• a wash bottle containing deionised water

• a retort stand and clamp

• weighing bottle (or equivalent)

• approximately 9.0 g of ammonium iron(II) sulfate

• access to an accurate balance (reading to 2 decimal places)

• glass rod

• spatula

• 250 cm3 of dilute sulfuric acid (approximately 1.0 mol dm–3) labelled dilute sulfuric acid and caution

• 150 cm3 of 0.02 mol dm–3 acidifi ed potassium manganate(VII) labelled potassium manganate(VII) solution.

8812.02 44 [Turn over


Question 2


• a small beaker

• fi ve test tubes

• a boiling tube

• a test tube holder

• a test tube rack

• a spatula

• a stirring rod

• a heat-proof mat

• a Bunsen burner

• several plastic droppers

• deionised water

• kettle to supply hot water (optional)

• hydrated copper(II) sulfate (approximately 3.0 g) labelled A

• about 10 cm3 of concentrated hydrochloric acid in a stoppered reagent bottle labelled concentrated hydrochloric acid and corrosive

• about 10 cm3 of an aqueous solution of 1,2-diaminoethane (approximately 0.2M) labelled 1,2-diaminoethane

• about 10 cm3 of an aqueous solution of sodium hydroxide (approximately 2.0M) labelled sodium hydroxide and corrosive

• a reagent bottle containing concentrated ammonia labelled concentrated ammonia and irritant (available in the fume cupboard(s)). Each candidate will only need about 10 cm3

• about 10 cm3 of aqueous solution of barium chloride (approximately 0.1M) labelled barium chloride solution

• about 10 cm3 of aqueous ethanoic acid (approximately 25% glacial 75% water) labelled B

• about 10 cm3 of aqueous potassium dichromate (approximately 0.1M) labelled potassium dichromate and irritant

• 2M sulfuric acid labelled dilute sulfuric acid and caution

• 2–3 g of sodium hydrogencarbonate

8812.02 5 5



Question 1






• three conical fl ask of 250 cm3 capacity



• one beaker of 250 cm3 capacity

• a wash bottle containing deionised/distilled water



• approximately 9.0 g of ammonium iron(II) sulfate


• glass rod

• spatula

• 250 cm3 of dilute sulfuric acid (approximately 1.0 mol dm–3) labelled dilute sulfuric acid and caution

• 150 cm3 of 0.02 mol dm–3 acidifi ed potassium manganate(VII) labelled potassium manganate(VII) solution.

8812.02 66 [Turn over


Question 2


• a small beaker


• a boiling tube



• a spatula

• a stirring rod


• a Bunsen burner


• deionised water


• hydrated nickel(II) sulfate (approximately 3.0 g) labelled X

• about 10 cm3 of an aqueous solution of edta (approx 0.1M) labelled edta

• about 10 cm3 of an aqueous solution of 1,2-diaminoethane (approximately 0.2M) labelled 1,2-diaminoethane

• about 10 cm3 of an aqueous solution of sodium hydroxide (approximately 2.0M) labelled sodium hydroxide

• a reagent bottle containing concentrated ammonia labelled concentrated ammonia and irritant (available in the fume cupboard(s)). Each candidate will only need about 10 cm3

• about 10 cm3 of aqueous solution of barium chloride (approximately 0.1M) labelled barium chloride solution

• about 10 cm3 of aqueous ethanoic acid (approximately 25% glacial 75% water) labelled Y

• about 10 cm3 of potassium dichromate (approximately 0.1M) labelled potassium dichromate and irritant

• 2M sulfuric acid labelled dilute sulfuric acid and caution

• 2–3 g of sodium hydrogencarbonate

8812.02 88 [Turn over

8812.03 [Turn over


2014

Chemistry


Practical Examinations 1 and 2

[AC231] [AC232]

THURSDAY 15 AND FRIDAY 16 MAY

Confidential Instructionsto the Supervisor

of the Practical Examination

8812.03 [Turn over

INSTRUCTIONS TO THE SUPERVISOR OF THE PRACTICAL EXAMINATION

General

1. The instructions contained in this document are for the use of the Supervisor and are strictly confidential. Under no circumstances may information concerning apparatus or materials be given before the examination to a candidate or other unauthorised person.

2. In a centre with a large number of candidates it may be necessary for two or more examination sessions to be organised. It is the responsibility of the schools to ensure

that there should be no contact between candidates taking each session.

3. A suitable laboratory must be reserved for the examination and kept locked throughout the period of preparation. Unauthorised persons not involved in the preparation for the examination must not be allowed to enter. Candidates must not be admitted until the specified time for commencement of the examination.

4. The Supervisor must ensure that the solutions provided for the candidates are of the nature and concentrations specified in the Apparatus and Materials List.

5. The Supervisor is to be granted access to the Teacher’s Copy of the Question Paper, showing parts of questions 1 and 2 only, on Monday 12 May 2014. The Supervisor is asked to check, at the earliest opportunity, that the experiments and tests in the question paper may be completed satisfactorily using the apparatus, materials and solutions that have been assembled. This question paper must then be returned to safe custody at the earliest possible moment after the Supervisor has ensured that all is in order. No access to the question paper should be allowed before 12 May 2014.

6. In the case of centres who have candidates entered for both practical examinations, the Supervisor must return all unused scripts of Practical Examination 1 to the Examinations Officer immediately on completion of the examination. The contents of

this examination must be kept confidential until the completion of Practical Examination 2.

7. Pipettes and burettes should be checked before the examination, and there should be an adequate supply of spare apparatus in case of breakages. The Apparatus and Materials List should be regarded as a minimum and there should be no objection to candidates being supplied with more than the minimum amount of apparatus and materials.

8. Candidates may not use text books and laboratory notes for reference during the examination, and must be informed of this beforehand.

8812.03 [Turn over

9. Clear instructions must be given by the Supervisor to all candidates at the beginning of the examination concerning appropriate safety procedures and precautions. Supervisors are also advised to remind candidates that all substances in the examination must be treated with caution. Only those tests specified in the question paper should be attempted. Candidates must not attempt any additional confirmatory tests. Anything

spilled on the skin should be washed off immediately with plenty of water. The use of appropriate eye protection is essential.

10. Supervisors are reminded that they may not assist candidates during the examination. However, if in the opinion of the Supervisor, a candidate is about to do something which may endanger him/herself or others, the Supervisor should intervene. A full written report must be sent to CCEA at once.

11. Upon request, a candidate may be given additional quantities of materials (answer paper, reagents and unknowns) without penalty. No notification need be sent to CCEA.

12. The examination room must be cleared of candidates immediately after the examination.

13. No materials will be supplied by CCEA.

8812.03 [Turn over

Northern Ireland Council for the Curriculum, Examinations andAssessment

General Certificate of Education

Advanced

Chemistry


Thursday 15 May 2014

This report must be completed by the Supervisor during the examination.The complete report should include all candidates taking this PracticalExamination. This Supervisor’s Report should be copied and attached toEach Advice Note bundle and returned to CCEA in the normal way.

Comments:

Supervisor’s Signature . . . . . . . . . . . . . . . . . . . Date . . . . . . . . . . .

71

Centre Number

Candidate Number

8812.03 [Turn over



Advanced

Chemistry


Friday 16 May 2014


Comments:


71

Centre Number

Candidate Number

8812.03


2014

8812.01F

MARKSCHEME



[AC231]


8812.01F 22 [Turn over

AVAILABLEMARKS

Annotation





General points







MARKING GUIDELINES







8812.01F 3 3

AVAILABLEMARKS

1 (a) (i) Mass between given values Mass to 2 decimal places Units Error [–1] [2]

(ii) Correct RFM for ammonium iron(II) sulfate (392) Correct calculation of moles Correct calculation of concentration Error [–1] [3] (b) Table [3] Significant figures [2] Calculation of average titre [2] Titration consistency [1] [8]

Table

Titration Initial burette reading/cm3

Final burette reading/cm3

Addedvolume/cm3

1

2

3 Average titre = cm3

Clearly labelled and neatly presented table, including units and the recording of the average titre. [3]

Significant figures All accurate titration readings recorded to one decimal place (including initial burette reading at 0.0 if used). Accept, however, 0.00 and 0.05 but penalise by [–1] if other readings are given to two or more decimal places. The use of 0 is penalised by [–1] if used (only penalise once). [2] Average titre Accurate titrations only should be used. The use of a rough value is [–1].

The average value can be calculated to two decimal places or more, e.g. 25.17 and 25.18 average to 25.175.



Titration consistency



AVAILABLEMARKS

(c) (i) Add solution from burette slowly/dropwise at end point [1], swirl the flask/wash down sides with deionised water etc. [1] [2] (ii) colourless to pink [1]

(d) (i) MnO4– + 8H+ + 5e– → Mn 2+ + 4H2O [2]

(ii) Fe2+ → Fe3+ + e– [1]

(iii) 5Fe2+ + 8H+ + MnO4– → 5Fe3+ + 4H2O + Mn2+ [2]

(iv) for a concentration of 0.09 mol dm–3 Fe2+ and a titration value of 20.1 cm3

25/1000 × 0.09 mol in 25 cm3 of Fe2+ solution = 2.25 × 10–3 mol

2.25 × 10–3/5 mol KMnO4 in 20.1 cm3 = 4.5 × 10–4 mol in 20.1 cm3

KMnO4 = 158; 4.5 × 10–4 mol = 158 × 4.5 × 10–4 g = 0.0711 g

0.0711 g in 20.1 cm3 = 0.0711/20.1 × 103 = 3.537 g = 3.54 g [4] 25

8812.01F 5 5

AVAILABLEMARKS



(a) (i) You are provided with a solid, labelled A. Carry out the following tests. Record your observations in the spaces below.

Test Observations

1 Describe the appearance of A. Blue solid/crystals/powder[1]

2 Dissolve two spatula measures of A in approximately 50 cm3 of water.

Keep this solution for use in further tests.Blue (solution)

[1]

3 Place 4 cm3 of the solution from test 2 in a test tube. Add an equal volume of concentrated hydrochloric acid. Yellow-green/Green solution

[1]4 Place 4 cm3 of the solution from test 2

in a test tube. Add an equal volume of 1,2-diaminoethane solution. Darker blue solution/

blue-violet/blue-purple[1]



Blue precipitate

Precipitate remains[2]


Deep blue solution forms[1]

7 Place 4 cm3 of the solution from test 2 in a test tube. Add 1 cm3 of barium chloride solution dropwise. White precipitate

[1]

(ii) hydrated [1] copper(II) sulfate [1] [2]

(iii) Suggest the formulae of the complex ions formed in tests 2, 3, 4 and 6.

Test 2 [Cu(H2O)6]2+ [1]

Test 3 [CuCl4]2– [1]

Test 4 [Cu(en)3]2+ [1]

Test 6 [Cu(NH3)4(H2O)2]2+ [1] [4]


AVAILABLEMARKS

(iv) Give the formula of the precipitates formed in tests 5 and 7.

Test 5 Cu(OH)2 [1]

Test 7 BaSO4 [1] [2]


Test Observations


ColourlessVinegar smell/sharp/irritating

[1]

2 Place 4 cm3 of the solution in a test tube. Add an equal volume of potassium dichromate solution and acidify with 1 cm3 of dilute sulfuric acid. Heat in a water bath for 5 minutes.

Solution remains orange [1]


Solid dissolvesbubbles/effervescence/fizzing

[2]

(ii) –COOH [1]

(iii) strong C O absorption [1] strong O H absorption [1] [2]

(iv) position of molecular ion gives RMM [1] uniqueness of fragmentation [1] [2] 25

8812.01F 7 7

AVAILABLEMARKS

3 Planning Exercise (a) (i) HCOOH + C2H5OH → HCOOC2H5 + H2O [1] (ii) Theoretical yield = 7.4 g or 0.1 mole [1] Min mass of ethanol 4.6 g [1] Min mass of methanoic acid 4.6 g [1] [3]

(b) Place ethanol and methanoic acid in a flask [1] add concentrated sulfuric acid [1] add anti-bumping granules (or equivalent) [1] reflux/distillation [1] collect crude product around 55 °C [1] [5]

Quality of written communication [2] (c) (i) Used to remove acid impurities [1] Shake the crude product with aqueous sodium carbonate [1] using a separating funnel and release pressure [1] separate the ester from the aqueous layer [1] [4]

(ii) Used to remove water [1] shake with anhydrous calcium chloride until clear and filter/decant [1] [2]

(d)

9 8 7 6 5 4 3 2 1 0

quartet and triplet [1] triplet closer to TMS [1] integration (2:3) [1] [3] 20

Total 70

ppm

TIME2 hours 30 minutes.

INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all three questions.Write your answers in the spaces provided.

INFORMATION FOR CANDIDATESThe total mark for this paper is 70.Questions 1 and 2 are practical exercises each worth 25 marks.Question 3 is a planning exercise worth 20 marks.Quality of written communication will be assessed in Question 3(b).You may not have access to notes, textbooks and other material to assist you.A Periodic Table of the Elements, containing some data, is included in this question paper.


2014

8813.03 R


Question Number


123

TotalMarks

Chemistry



[AC232]

FRIDAY 16 MAY, MORNING

Centre Number

71

Candidate Number

*AC232*

AC

232

8813.03 R 2



You are required to dissolve a weighed sample of ammonium iron(II) sulfate in dilute sulfuric acid and make the solution up to 250 cm3 in a volumetric flask. You will then titrate 25.0 cm3 portions of this solution with acidified potassium manganate(VII). You will then use your results to calculate the concentration of the acidified potassium manganate(VII) solution.


• Hydratedammoniumiron(II)sulfate,(NH4)2Fe(SO4)2.6H2O • Dilutesulfuricacid • Deionisedwater • A250cm3 volumetric flask • Anacidifiedsolutionofpotassiummanganate(VII)

(a) (i) Weigh out between 8.80 and 8.90 g of ammonium iron(II) sulfate. Record the mass to two decimal places.

Massof(NH4)2Fe(SO4)2.6H2O [2]

(ii)Dissolvetheweighedsampleinapproximately100cm3 of dilute sulfuric acid and make the solution up to 250 cm3 in the volumetric flask using deionised water. Calculate the concentration of the solution in mol dm–3.

[3]

8813.03 R 3 [Turn over


(b) Titrate 25.0 cm3 portions of your solution with acidified potassium manganate(VII). Record your results in a suitable table in the space below. Calculate the average titre.

[8]

(c) (i) Describehowyouensuredtheendpointofyourtitrationwasaccurate.

[2]

(ii) State the colour change at the end point of your titration.

[1]

8813.03 R 4


(d) (i) Write the half-equation for the reduction of acidified manganate(VII) ions to form manganese(II) ions.

[2]

(ii) Write the half-equation for the oxidation of iron(II) ions to form iron(III) ions.

[1]

(iii) Write the ionic equation for the reaction.

[2]

(iv) Calculate the concentration of the acidified potassium manganate(VII) solution in g dm–3.

[4]


blANk pAGE(Questions continue overleaf)

8813.03 R 6




(a) (i) You are provided with a solid, labelled X. Carry out the following tests. Record your observations in the spaces below.

Test Observations

1DescribetheappearanceofX.

[1]

2DissolvetwospatulameasuresofXin approximately 50 cm3 of water.

Keep this solution for use in further tests.

[1]


Add an equal volume of concentrated hydrochloric acid.

[1]


Add an equal volume of 1,2-diaminoethane solution. [1]


(b) Add a further 5 cm3 of sodium hydroxide solution. [2]


[1]

7 Place 4 cm3 of the solution from test 2 in a test tube. Add 1 cm3 of barium chloride solution dropwise.

[1]

(ii) Identify X.

[2]



(iii) Write the formula of the complex ion formed in test 2.

[1]

(iv) Write the formula of the complex ion formed in test 3.

[1]

(v) Write an ionic equation for the reaction occurring in test 4.

[2]

(vi) Write an ionic equation for the reaction occurring in test 6.

[2]

8813.03 R 8


(b) (i) You are provided with an aqueous solution of an organic compound Y. Carry out the following tests. Record your observations in the spaces below.

Test Observations

1Describethesolution.Includeadescription of its smell.

[1]

2 Place 4 cm3 of the solution in a test tube. Add an equal volume of potassium dichromate solution and acidify with 1 cm3 of dilute sulfuricacid.Heatinawaterbathfor five minutes. [1]

3 Place 4 cm3 of the solution in a test tube. Add half a spatula measure of sodium hydrogencarbonate. [2]

(ii) Identify the functional group present in Y.

[1]

(iii) Suggest how the infrared spectrum of Y could confirm the presence of this functional group.

[2]

(iv) Suggest how the mass spectrum of Y could confirm its identity.

[2]


blANk pAGE(Questions continue overleaf)

8813.03 R 10


3 planning exercise

Ethyl 3-nitrobenzoate exists as a solid at room temperature and pressure. Its melting point is 42 °C.

COOC2H5

NO2

(a) (i) Write the equation for the formation of ethyl 3-nitrobenzoate from ethyl benzoate.

[1]

(ii) Assuming a 60% yield, calculate the minimum mass of the organic reactant required to produce 5.85 g of ethyl 3-nitrobenzoate.

[2]

(b) Describethelaboratorypreparationofethyl3-nitrobenzoateupto and including the removal of the crude product from the reaction mixture.

[5]


8813.03 R 11 [Turn over


(c) (i) The crude product is recrystallised before its melting point is determined. Explain why recrystallisation is carried out and, giving experimental details, describe the process of recrystallisation.

[4]

(ii) Howwouldthecrystalsbedriedbeforethemeltingpointisdetermined?

[1]

(iii) Howwouldyouusethemeltingpointtodeterminewhetherthecrystals are pure ethyl 3-nitrobenzoate?

[2]

8813.03 R 12


(d) Part of the nmr spectrum for ethyl 3-nitrobenzoate is shown below. The aromatic protons are shown. Complete the nmr spectrum in terms of integration and splitting pattern.

1 02345

ppm

6789

THIS IS THE END OF THE QUESTION pApER

[3]

8813.03 R



2014

Chemistry


Practical Examination 2 [AC232]

FRIDAY 16 MAY

8812.05 R

APPARATUSAND

MATERIALSLIST

*AC232*

AC

232

Updated version for Practical Examination 2

8812.05 R 22 [Turn over

Advice for centres

● All chemicals used should be at least laboratory reagent specification and labelled with appropriate safety symbols, e.g. irritant.

● For centres running multiple sessions – candidates for the later session should be supplied with clean, dry glassware. If it is not feasible then glassware from the first session should be thoroughly washed, rinsed with deionised water and allowed to drain.

● Ensure all chemicals are in date otherwise expected observations may not be seen.

8812.05 R 3 3



Question 1






• three conical fl asks of 250 cm3 capacity



• one beaker of 250 cm3 capacity

• a wash bottle containing deionised/distilled water



• approximately 9.0 g of ammonium iron(II) sulfate labelled as ammonium iron(II) sulfate and HARMFUL


• glass rod

• spatula

• 250 cm3 of dilute sulfuric acid (approximately 1.0 mol dm–3) labelled dilute sulfuric acid and CAUTION and IRRITANT

• 150 cm3 of 0.02 mol dm–3 acidifi ed potassium manganate(VII) labelled potassium manganate(VII) solution and HARMFUL.

8812.05 R 44 [Turn over


Question 2


• a small beaker


• a boiling tube



• a spatula

• a stirring rod


• a Bunsen burner


• deionised water


• hydrated copper(II) sulfate (approximately 3.0 g) labelled X and HARMFUL

• about 10 cm3 of concentrated hydrochloric acid in a stoppered reagent bottle labelled concentrated hydrochloric acid and CORROSIVE

• about 10 cm3 of an aqueous solution of 1,2-diaminoethane (approximately 0.2M) labelled 1,2-diaminoethane and IRRITANT

• about 10 cm3 of an aqueous solution of sodium hydroxide (approximately 2.0M) labelled sodium hydroxide and CORROSIVE

• a reagent bottle containing concentrated ammonia labelled concentrated ammonia and CORROSIVE (available in the fume cupboard(s)). Each candidate will only need about 10 cm3

• about 10 cm3 of aqueous solution of barium chloride (approximately 0.1M) labelled barium chloride solution and HARMFUL

• about 10 cm3 of aqueous ethanoic acid (approximately 25% glacial 75% water) labelled Y and IRRITANT

• about 10 cm3 of aqueous potassium dichromate (approximately 0.1M) labelled potassium dichromate and TOXIC

• 2M sulfuric acid labelled dilute sulfuric acid and CORROSIVE

• 2–3 g of sodium hydrogencarbonate labelled sodium hydrogencarbonate.

8812.05 R 5 5

8812.05 R 66 [Turn over

8812.05 R 88 [Turn over

8812.03 [Turn over


2014

Chemistry


Practical Examinations 1 and 2

[AC231] [AC232]

THURSDAY 15 AND FRIDAY 16 MAY



8812.03 [Turn over


General






5. The Supervisor is to be granted access to the Teacher’s Copy of the Question Paper, showing parts of questions 1 and 2 only, on Monday 12 May 2014. The Supervisor is asked to check, at the earliest opportunity, that the experiments and tests in the question paper may be completed satisfactorily using the apparatus, materials and solutions that have been assembled. This question paper must then be returned to safe custody at the earliest possible moment after the Supervisor has ensured that all is in order. No access to the question paper should be allowed before 12 May 2014.

6. In the case of centres who have candidates entered for both practical examinations, the Supervisor must return all unused scripts of Practical Examination 1 to the Examinations Officer immediately on completion of the examination. The contents of

this examination must be kept confidential until the completion of Practical Examination 2.



8812.03 [Turn over







8812.03 [Turn over



Advanced

Chemistry


Thursday 15 May 2014


Comments:


71

Centre Number

Candidate Number

8812.03 [Turn over



Advanced

Chemistry


Friday 16 May 2014


Comments:


71

Centre Number

Candidate Number

8812.03


2014

8813.01F

MARKSCHEME



[AC232]

FRIDAY 16 MAY, MORNING


AVAILABLEMARKS

Annotation





General points







MARKING GUIDELINES







8813.01F 3 3

AVAILABLEMARKS

1 (a) (i) Mass between given values Mass to 2 decimal places Units Error [–1] [2]

(ii) Correct RFM for ammonium iron(II) sulfate (392) Correct calculation of moles Correct calculation of concentration Error [–1] [3] (b) Table [3] Significant figures [2] Calculation of average titre [2] Titration consistency [1] [8]

Table

Titration Initial burettereading/cm3

Final burette reading/cm3

Volumeadded/cm3

1

2

3 Average titre = cm3

Table [3] The Table should be drawn as a table. It should be labelled with the following: initial burette reading, final burette reading and the titre. It is not necessary to use exactly these words but there should be appropriate

columns and rows [1]. Units, i.e. cm3, should be stated [1]. The rough titration value should not be the same as the accurate values [1].

Significant figures [2] All accurate titration readings recorded to one decimal place (including initial burette reading at 0.0 if used). Accept, however, 0.00 and 0.05 but penalise by [–1] if other readings are given to two or more decimal places. The use of 0 is penalised by [–1] if used (only penalise once). Average titre [2] Accurate titrations only should be used. The use of a rough value is [–1].

The average value can be calculated to two decimal places or more, e.g. 25.17 and 25.18 average to 25.175.



Titration consistency



AVAILABLEMARKS

(c) (i) add solution from burette slowly/dropwise at end point [1] swirl the flask/wash down the sides with deionised water etc. [1] [2]

(ii) colourless to pink [1]

(d) (i) MnO4– + 8H+ + 5e– → Mn2+ + 4H2O [2]

(ii) Fe2+ → Fe3+ + e– [1]

(iii) 5Fe2+ + 8H+ + MnO4– → 5Fe3+ + 4H2O + Mn2+ [2]

(iv) for a concentration of 0.09 mol dm–3 Fe2+ and a titration value of 20.1 cm3

25/1000 × 0.09 mol in 25 cm3 of Fe2+ solution = 2.25 × 10–3 mol

2.25 × 10–3/5 mol KMnO4 in 20.1 cm3 = 4.5 × 10–4 mol in 20.1 cm3

KMnO4 = 158; 4.5 × 10–4 mol = 158 × 4.5 × 10–4 g = 0.0711 g

0.0711 g in 20.1 cm3 = 0.0711/20.1 × 103 = 3.537 g = 3.54 g [4] 25

8813.01F 5 5

AVAILABLEMARKS



(a) (i) You are provided with a solid, labelled X. Carry out the following tests. Record your observations in the spaces below.

Test Observations

1 Describe the appearance of X. Blue solid/crystals/powder[1]

2 Dissolve two spatula measures of X in approximately 50 cm3 of water.

Keep this solution for use in further tests.Blue (solution)

[1]

3 Place 4 cm3 of the solution from test 2 in a test tube. Add an equal volume of concentrated hydrochloric acid. Yellow-green/Green solution

[1]4 Place 4 cm3 of the solution from test 2

in a test tube. Add an equal volume of 1,2-diaminoethane solution. Darker blue solution/

blue-violet/blue-purple[1]



Blue precipitate

Precipitate remains[2]


Deep blue solution forms[1]

7 Place 4 cm3 of the solution from test 2 in a test tube. Add 1 cm3 of barium chloride solution dropwise. White precipitate

[1]

(ii) hydrated [1] copper(II) sulfate [1] [2]

(iii) [Cu(H2O)6]2+ [1]

(iv) [CuCl4]2– [1]

(v) [Cu(H2O)6]2+ + 3 en [Cu(en)3]2+ + 6 H2O [2]

(vi) [Cu(H2O)6]2+ + 4 NH3 [Cu(NH3)4 (H2O)2]2+ + 4 H2O [2]


AVAILABLEMARKS


Test Observations


ColourlessVinegar smell/sharp/irritating

[1]

2 Place 4 cm3 of the solution in a test tube. Add an equal volume of potassium dichromate solution and acidify with 1 cm3 of dilute sulfuric acid. Heat in a water bath for five minutes.

Solution remains orange [1]


Solid dissolvesbubbles/effervescence/fizzing

[2]

(ii) –COOH [1]

(iii) strong C O absorption [1] strong O H absorption [1] [2]

(iv) position of molecular ion gives RMM [1] uniqueness of fragmentation [1] [2] 25

8813.01F 7 7

AVAILABLEMARKS

3 Planning Exercise

(a) (i) C6H5COOC2H5 + HNO3 → C6H4NO2COOC2H5 + H2O [1] (ii) Theoretical yield = 9.75 g or 0.05 mole [1] Min mass of ethyl benzoate 7.5 g [1] [2]

(b) Place concentrated sulfuric and concentrated nitric acid in a flask [1] Add slowly to ethyl benzoate [1] temperature kept below 15 °C [1] pour reaction mixture onto crushed ice [1] filter [1] [5]

Quality of written communication [2] (c) (i) To remove impurities [1] dissolve in minimum amount of hot ethanol/methanol [1] filter while hot allow (filtrate) to cool/crystals to form [1] vacuum filtration for crystals [1] [4]

(ii) between filter papers/cool oven/desiccator [1]

(iii) sharp m. pt [1] compare to 42°C [1] [2] (d)

quartet and triplet [1] triplet closer to TMS [1] integration (2:3) [1] [3] 20 Total 70

1 02345

ppm

6789

TIME1 hour 15 minutes.

INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer both questions.Write your answers in the spaces provided.

INFORMATION FOR CANDIDATESThe total mark for this paper is 20.Question 1 is a practical exercise worth 8 marks.Question 2 is a practical exercise worth 12 marks.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Periodic Table of Elements (including some data) is provided.You may not have access to notes, textbooks and other material to assist you.

9568

Question Number

Marks


12

TotalMarks

Centre Number

Candidate Number

Chemistry

Assessment Unit A2 3assessing

Module 3: Practical ExaminationPractical Booklet A

[AC233]TUESDAY 5 MAY, MORNING


2015

*AC233*

AC

233

BLANK PAGE

9568 2

9568 3 [Turn over


Practical Booklet A

Safety glasses must be worn at all times and care should be exercised during the practical examination.


You are required to titrate standard sodium thiosulfate solution against iodine liberated by the reaction of a solution of potassium iodate(V) with acidified potassium iodide solution.

You are provided with the following: a solution of potassium iodate(V) four 20 cm3 portions of sulfuric acid potassium iodide solution sodium thiosulfate solution of concentration 0.10 mol dm−3

starch indicator

1. Rinse and fill the burette with the appropriate solution. 2. Use a measuring cylinder to pour 10 cm3 of potassium iodide solution

into a 250 cm3 conical flask. 3. Add 20 cm3 of dilute sulfuric acid to the solution in the conical flask. 4. Use a measuring cylinder to add 5 cm3 of potassium iodate(V) solution

to the acidified potassium iodide solution. 5. Titrate 0.10 mol dm−3 sodium thiosulfate solution against the iodine

formed.

Present your results in a suitable table and calculate the average titre.

Results table

[8]


9568 4

2 Observation exercise

(a) You are provided with a salt, labelled X. Carry out the following tests on X and record your observations in the table below.

Test Observations

1 Describe the appearance of X. [1]

2 Add 3 spatula measures of X to 20 cm3 of water and stir until there is no further change. Use this solution for tests 3, 4 and 5. [1]

3 (a) In a fume cupboard add 5 drops of concentrated ammonia solution to 2 cm3 of the solution of X in a test tube.

(b) Add a further 5 cm3 of concentrated ammonia solution to the test tube. [2]

4 (a) Add 5 drops of sodium hydroxide solution to 2 cm3 of the solution of X in a test tube.

(b) Add a further 5 cm3 of sodium hydroxide solution to the test tube. [2]

5 Add 2 cm3 of barium chloride solution to a test tube containing 2 cm3 of the solution of X. [1]

6 Place a half spatula measure of X onto a watch glass in a fume cupboard. Wearing gloves, slowly add 10 drops of concentrated sulfuric acid to X. [1]

7 Place a spatula measure of X in a dry boiling tube. Heat the boiling tube gently.

[2]


9568 5

(b) You are provided with an organic liquid labelled Y. Carry out the following tests and record your observations in the table below.

N.B. Water bath filled using hot water from a kettle.

Test Observations1 Add 10 drops of Y to 2 cm3 of

acidified potassium dichromate solution in a test tube. Place the test tube in a hot water bath for 5 minutes. [1]

2 Add 1 cm3 of Y to 2 cm3 of Fehling’s solution in a test tube. Place the test tube in a hot water bath for 5 minutes. [1]


200372



2015

Chemistry

Assessment Unit A2 3assessing


[AC233]


9568.02

APPARATUSAND

MATERIALSLIST

*AC233*

AC

233

9568.02 22 [Turn over

Advice for centres

• All chemicals used should be at least laboratory reagent specification and labelled with appropriate safety symbols, e.g. irritant.

• For centres running multiple sessions – candidates for the later session should be supplied with clean, dry glassware. If it is not feasible then glassware from the first session should be thoroughly washed, rinsed with deionised water and allowed to drain.

• Ensure all chemicals are in date otherwise expected observations may not be seen.

9568.02 3 3

Practical Examination


Question 1


• one 50 cm3 burette of at least class B quality;

• a funnel for filling the burette;

• a retort stand and clamp;

• a beaker of 100 cm3 capacity;

• two 10 cm3 measuring cylinders;

• a plastic dropper;

• three conical flasks of 250 cm3 capacity;

• a white tile or white paper;

• a wash bottle containing deionised water;

• 150 cm3 of 0.10 mol dm–3 sodium thiosulfate solution labelled sodium thiosulfate solution 0.10 mol dm–3;

• sulfuric acid 4 × 20 cm3 portions of approximately 2 mol dm–3 sulfuric acid solution labelled sulfuric acid, corrosive and irritant;

• 4 × 10 cm3 portions of 1M potassium iodide solution, labelled potassium iodide solution;

• 150 cm3 of approximately 0.10 mol dm–3 potassium iodate(V) solution labelled potassium iodate(V) solution and oxidising;

• starch indicator 2% (w/v) with dropper. Add 2 g of starch to a small amount of water, make into a paste. Make up to 100 cm3 in boiling water. Labelled starch indicator.

Appropriate amounts should be prepared for the total number of candidates taking theexamination.

9568.02 44 [Turn over

Question 2

Candidates should have access to a fume cupboard.


• small beaker (100 cm3);

• six test tubes;

• one boiling tube;

• a test tube rack;

• a spatula;

• a heatproof mat;

• a Bunsen burner;

• several plastic droppers;

• one 250 cm3 beaker;

• one pair of gloves;

• tongs;

• a watch glass;

• about 3.0 g of hydrated iron(II) sulfate, labelled X;

• about 10 cm3 of barium chloride solution in a reagent bottle/beaker labelled barium chloride solution. This solution should be approximately 0.1 M (20.8 g/dm3 for BaCl2 or 24.4 g/dm3 for BaCl2.2H2O);

• about 10 cm3 of sodium hydroxide solution in a reagent bottle/beaker labelled sodium hydroxide solution and corrosive. This solution should be approximately 2 mol dm–3;

• a reagent bottle containing concentrated ammonia solution labelled concentrated ammonia solution and irritant (Placed in fume cupboard);

• a reagent bottle containing concentrated sulfuric acid labelled concentrated sulfuric acid and corrosive (Placed in fume cupboard);

• about 10 cm3 of ethanal in a stoppered container labelled Y, flammable and harmful;

• 10 cm3 of Fehling’s solution (a mix of equal volumes of Fehling’s No 1 and Fehlings No 2) labelled Fehling’s solution and corrosive;

• about 5 cm3 of potassium dichromate(VI) solution in a stoppered reagent bottle labelled acidified potassium dichromate solution and irritant. This solution should be about 0.1 mol dm–3, made by dissolving 30 g of potassium dichromate(VI) in 100 cm3 of

1 mol dm–3 sulfuric acid and made up to 1 dm3 with deionised water;

• access to a kettle.

9568.02 5 5

Risk Assessment

The risk assessment below applies both to the preparation of the materials for the practical examination as well as the conducting of the examination.

Care should be taken when handling glassware, and breakages should be removed immediately and disposed of safely.

Candidates should only conduct the tasks as described in the practical exam.

Under no circumstances should ethanal be heated with a naked flame; a water bath must be used. If hot water is obtained from a kettle, the kettle should be PAT tested and be labelled as such.

Question 1

Sodium thiosulfate is low hazard, if contact is made with eyes or mouth wash with water.EMERGENCY ACTION

• In the eye. Flood the eye with gently-running tap water for 10 minutes. See a doctor if pain persists.

• Swallowed. Do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.

• Spilt on the skin or clothing. Brush solid off contaminated clothing. Rinse clothing or the skin as necessary.

• Spilt on the floor, bench, etc. Brush up solid spills, trying to avoid raising dust, then wipe with a damp cloth. Wipe up solution spills with a cloth and rinse it well.

Sulfuric acid (2.0 M) is corrosive and can cause severe burns, care should be taken to avoid contact with skin and eyes. If handling larger quantities gloves should be worn.EMERGENCY ACTION

• In the eye. Flood the eye with gently-running tap water for 10 minutes. See a doctor.


• Spilt on the skin or clothing. Remove contaminated clothing. Especially with concentrated acid, quickly use a dry cloth or paper towel to wipe as much liquid as possible off the skin. Then drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.

• Spilt on the floor, bench etc. Wipe up small amounts with a damp cloth and rinse it well. For larger amounts and especially for (moderately) concentrated acid, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with sodium carbonate. Rinse with plenty of water.

9568.02 66 [Turn over

Potassium iodide is low hazard, if contact is made with eyes or mouth wash with water.EMERGENCY ACTION




• Spilt on the floor, bench etc. Brush up solid spills, trying to avoid raising dust, then wipe with a damp cloth. Wipe up solution spills with a cloth and rinse it well.

Potassium iodate is an oxidising agent and may also cause irritation to the skin and eyes, care should be taken to avoid contact with the skin.EMERGENCY ACTION




• Spilt on the floor, bench, etc. Brush up solid spills, trying to avoid raising dust, then wipe with a damp cloth. Wipe up solution spills with a cloth and rinse it well.

• Disposal. 50 g should be dissolved in 1 litre of water before pouring down a drain.

Starch solution may be an irritant to the skin and eyes.If contact is made with skin or eyes it should be flushed with copious amounts of water and medical advice sought if necessary.

9568.02 7

Question 2

Iron sulfate is harmful if swallowed.EMERGENCY ACTION

• In the eye. Flood the eye with gently-running tap water for at least 10 minutes. See a doctor.


• Dust breathed in. Remove the casualty to fresh air. See a doctor if breathing is difficult.

• Spilt on the skin or clothing. Remove contaminated clothing and rinse it. Wash off the skin with plenty of water.

• Spilt on the floor, bench, etc. Scoop up solid (take care not to raise dust). Wipe up small solution spills or any traces of solid with cloth. For larger spills use mineral absorbent (e.g. cat litter).

• Disposal. Dilute to below 0.2 M and pour down a drain.

Barium chloride is toxic if swallowed, harmful by inhalation and irritating to the eyes, skin and lungs. Wash hands after handling barium compounds.EMERGENCY ACTION

• In the eye. Flood the eye with gently-running tap water for at least 20 minutes. See a doctor. If a visit to hospital is necessary, continue washing the eye during the journey in an ambulance.


• Spilt on the skin or clothing. Remove contaminated clothing. Drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.

• Spilt on the floor, bench, etc. Wipe up small amounts with a damp cloth and rinse it well. For larger amounts, and especially for (moderately) concentrated solutions, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Rinse with plenty of water.

• Disposal. Dilute to below 0.05 M and pour down a drain.

Sodium hydroxide. It causes severe burns; it is particularly dangerous to the eyes. Small amounts should be used. Gloves should be worn if larger amounts are used.EMERGENCY ACTION

• In the eye. Flood the eye with gently-running tap water for at least 20 minutes. See a doctor. If a visit to hospital is necessary, continue washing the eye during the journey in an ambulance.



• Spilt on the floor, bench, etc. Wipe up small amounts with a damp cloth and rinse it well. For larger amounts and especially for (moderately) concentrated solutions, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with citric acid. Rinse with plenty of water.

Ammonia solution is corrosive and causes burns and is dangerous to the eyes, goggles should be worn, and ammonia causes severe internal damage if swallowed.EMERGENCY ACTION

• In the eye. Flood the eye with gently-running tap water for at least 20 minutes (for alkalis). See a doctor. If it is necessary to go to hospital continue washing the eye during the journey in an ambulance.

• Vapour breathed in. Remove the casualty to fresh air. Call a doctor if breathing is difficult.



• Spilt on the floor, bench etc. Consider the need to evacuate the laboratory and open windows if large amounts

are spilt and especially for (moderately) concentrated solutions. Cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with citric acid. Rinse with plenty of water. Wipe up small amounts with a damp cloth and rinse it well.

9568.02 8

9568.02 9 9

Sulfuric acid is corrosive, causing severe burns and reacts violently with water. Ifhandling larger amounts, gloves could be worn.EMERGENCY ACTION

• In the eye. Flood the eye with gently-running tap water for 10 minutes. See a doctor.


• Spilt on the skin or clothing. Remove contaminated clothing. Especially with concentrated acid, quickly use a dry cloth or paper towel to wipe as much liquid as possible off the skin. Then drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.

• Spilt on the floor, bench, etc. Wipe up small amounts with a damp cloth and rinse it well. For larger amounts, and especially for (moderately) concentrated acid, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with sodium carbonate. Rinse with plenty of water.

Ethanal is extremely flammable and can be irritating to the eyes and respiratory system. Ethanal may boil spontaneously and should be cooled before use.EMERGENCY ACTION

• In the eye. Immediately rinse the eye with gently-running water for 10 minutes. See a doctor.

• Vapour breathed in. Remove the casualty to fresh air. Keep him/her warm. See a doctor if breathing is difficult.


• Spilt on the skin or clothing. Remove contaminated clothing. Wash the affected area and clothing with plenty of water.

• Spilt on the floor, bench etc. Put out all Bunsen burner flames. Wipe up small amounts with a cloth and rinse it well. For larger amounts, open all windows, cover with mineral absorbent (e.g. cat litter), and scoop into a bucket and add water.

Fehling’s solution contains concentrated sodium hydroxide solution (see entry for sodium hydroxide above) as well as copper(II) sulfate which is low hazard.EMERGENCY ACTION (see sodium hydroxide above)

9568.02 1010 [Turn over

Potassium dichromate is toxic by inhalation and if swallowed may cause ulcers. Potassium dichromate is also oxidising and may be carcinogenic by inhalation, however inhalation is unlikely in school use.

EMERGENCY ACTION

• In the eye. Flood the eye with gently-running tap water for at least 10 minutes See a doctor.


• Spilt on the skin or clothing. Remove contaminated clothing and rinse it until no colour remains. Wash off the skin with plenty of water. If skin contamination is more than small, see a doctor.

• Spilt on the floor, bench, etc. Wear eye protection and gloves. Scoop up the solid. Rinse the area with water and wipe up, rinsing repeatedly until no colour remains. Rinse the mop or cloth thoroughly.

9568.02 [Turn over

9568.06 [Turn over


2015

Chemistry

Assessment Unit A2 3Practical Assessment

Practical Booklet A

[AC233]

TUESDAY 5 MAY



9568.06 [Turn over


General






5. The Supervisor is to be granted access to the Teacher’s Copy of Practical Booklet A on Wednesday 29 April 2015. The Supervisor is asked to check, at the earliest

opportunity, that the experiments and tests in the question paper may be completed satisfactorily using the apparatus, materials and solutions that have been assembled. This question paper must then be returned to safe custody at the earliest possible moment after the Supervisor has ensured that all is in order. No access to the question paper should be allowed before 29 April 2015.

6. Centres may need to carry out multiple sessions to accommodate all their candidates sitting Practical Booklet A in a laboratory. Supervision must take place from 30 minutes after the scheduled starting time of the examination, as set out in the timetable, until the time when the candidate(s) begin(s) their examination(s). This is in order to ensure that there is no contact with other candidates. The centre must appoint a member of staff from the centre to supervise the candidate at all times while he/she is on the premises.



9568.06 [Turn over







9568.06 [Turn over



Advanced

Chemistry

Practical Booklet A

Tuesday 5 May 2015


Comments:


71

Centre Number

Candidate Number

9568.06 [Turn over

9568.01 F


assessing


[AC233]


MARKSCHEME


2015

9568.01 F 2 [Turn over

AVAILABLEMARKS

Annotation





General points







MARKING GUIDELINES







9568.01 F 3

AVAILABLEMARKS


Titration Exercise

1 Table [3]

The Table should be drawn as a boxed table. It should be labelled with the following:

initial burette reading, final burette reading and the titre. It is not necessary to use exactly these words but there should be appropriate columns and rows. The recorded readings should be checked for mathematical accuracy [1].

The rough titration value should be greater than the accurate values (no more than 2 cm3) [1]. If rough less than accurate [–1].

Units, i.e. cm3, should be stated in each column/row [1].

Use of decimal places [2] All burette readings should be to at least one decimal place – each mistake is penalised by one mark. (However initial burette readings of 0 are penalised once only.) If used, the second decimal place position should be 0 or 5 only – other values will be penalised by 1 mark for each.

Average titre [2] Accurate titrations only should be used. All accurate titration values should be

used. The use of a rough value is [–1].

The average value can be calculated to two decimal places or more, e.g. 25.15 and 25.20 would average to 25.175. If three (or more) accurate titres are recorded, then the average titre must be calculated using all three (or more) accurate titres. Any error is [–1]. This might be an incorrect calculation or the omission of units. If the average titre is included in the table then the units indicated on the table apply.

Titration consistency [1] This is the difference within the accurate titrations. If three (or more) accurate

values are given then the difference between highest and lowest is used.

Difference Mark 0.3 [1] >0.3 [0] This value of 0.1 might need to be raised in the light of candidate response. [8] 8


AVAILABLEMARKS

2 (a) Test Observations

1 Describe the appearance of X. (Pale) green (crystals) [1]

2 Add 3 spatula measures of X to 20 cm3 of water and stir until there is no further change. Use this solution for tests 3, 4 and 5.

Yellow/green solution

[1]

3 (a) In a fume cupboard add 5 drops of concentrated ammonia solution to 2 cm3 of the solution of X in a test tube.


Green precipitate [1]

Precipitate colour darkens/remains [1]

4 (a) Add 5 drops of sodium hydroxide solution to 2 cm3 of the solution of X in a test tube.


Green precipitate [1]

Precipitate remains [1]

5 Add 2 cm3 of barium chloride solution to a test tube containing 2 cm3 of the solution of X.

White precipitate [1]

6 Place a half spatula measure of X onto a watch glass in a fume cupboard. In the fume cupboard and wearing gloves, slowly add 10 drops of concentrated sulfuric acid.

White solid [1] – not crystals

7 Place a spatula measure of X in a dry boiling tube. Heat the boiling tube gently.

White solid [1] – not crystals

Colourless liquid forms on walls of tube [1]

(b) Water bath filled using hot water from a kettle.

Test Observations

1 Add 10 drops of Y to 2 cm3 of acidified potassium dichromate solution in a test tube. Place the test tube in a hot water bath for 5 minutes.

(Orange to) green [1]

2 Add 1 cm3 of Y to 2 cm3 of Fehling's solution in a test tube. Place the test tube in a hot water bath for 5 minutes.

Red precipitate [1]

12

Total 20

MARKSCHEME


9569.01 F


2015


assessing

Module 3: Practical ExaminationPractical Booklet B

[AC234]

MONDAY 11 MAY, MORNING

29569.01 F

Annotation





General points







MARKING GUIDELINES





3

AVAILABLE MARKS

9569.01 F

1 (a) (i) 5Fe2+ + MnO4– + 8H+ → 4H2O + 5Fe3+ + Mn2+ [2]

(ii) pink [1]

(iii) MnO4– [1]

(iv) Performing a rough titration [1] adding dropwise before the endpoint [1] repeat for values within 0.1 cm3 [1] Any 2 from 3 [2] (b) Weigh (6.0g of) tablets on a balance In a beaker add (50 cm3) of deionised water to the tablets _`

a

Stir to dissolve Transfer with washings into a 250 cm3 volumetric flask _

`a Make up to the mark with deionised water/bottom of meniscus on line

(Stopper) and invert max [4]

(c) 22.4/1000 × 0.02 = 0.000448 Moles Fe2+ = 0.000448 × 5 = 0.00224 in 25 cm3

= 0.0224 in 250 cm3

RFM FeSO4.6H2O = 260 Mass FeSO4 = 0.0224 × 260 = 5.824g % = 5.824/6.00 × 100 = 97.07% [4]

(d) (i) blood red (solution) [1]

(ii) [Fe(H2O)6]3+ + SCN– → [Fe(H2O)5(SCN)]2+ + H2O [2] 17

4

AVAILABLE MARKS

9569.01 F

2 (a) (i) Based on the following observations, make deductions for salt A.

Test Deductions

1 Dissolve A in 20 cm3 of water

2 Add a few drops of concentrated ammonia solution to 2 cm3 of the solution of A in a test tube.

Confirms Fe3+/iron(III) hydroxide formed [1]/Fe(III)

3 Add 1 cm3 of barium chloride solution to 2 cm3 of the solution of A in a test tube, allow the mixture to settle.

Sulfate (ions) present [1]

(ii) Fe2(SO4)3 [1]

5

AVAILABLE MARKS

9569.01 F

(b) (i) Interpret the following data and identify the structural formula of the organic compound B, which has the empirical formula C2H4O.



Colourless liquid.

Pungent smell

2 Add 2 cm3 of deionised water to 2 cm3 of B in a test tube

One layer forms. B is miscible with water/completely soluble/–OH group present/can hydrogen bond (with water). [1]

3 Add 10 drops of B to 2 cm3 of acidifi ed potassium

dichromate solution in a test tube. Place the test tube in a hot water bath.

Solution stays orange.

Not an aldehyde or primary or secondary alcohol/ Possibly a tertiary alcohol/ketone/ carboxylic acid. [1]

4 Place 2 cm3 of B into a test tube. In a fume cupboard cautiously add a very small spatula measure of phosphorus(V) chloride to the test tube.

Fizzing.

Solid dissolves.

White fumes.

–OH present. –COOH present.

[1]

5 Place 5 cm3 of B in a boiling tube. Add 5 cm3 of ethanol, and then 1 cm3 of concentrated sulfuric acid. Heat the boiling tube in a water bath. Cautiously smell the contents of the boiling tube.

Sweet smell Ester (produced).–COOH present.

[1]

6 Add a spatula measure of sodium carbonate to 2 cm3 of B in a test tube.

Fizzing.

Solid dissolves.

CO2 released.

B is a carboxylic acid. [2]

(ii) Carboxylic acid(s) [1]

(iii)

CC

H H

C

H

H H

O

H O H

H

C

or

CH

H H

C

O

O H

H

C

C HH

H

[2]

(iv) +CH2COOH/CH2COOH+/C2H3O2+ [1] 13

6

AVAILABLE MARKS

9569.01 F

3 (a) Ammonia is a nucleophile [1]

(b) (i) Repeated boiling and condensing of a reaction mixture. [1]

(ii)Thermometer

Distillate/nitrobenzene

Heat

Condenser

Round-bottomed flask

Reaction mixture

no heat source [–1] no double jacket on condenser [–1] distillation fl ask open at top [–1] thermometer missing [–1], bulb not opposite side arm [–1] no labels [–1] If water in and out IS shown [–1] sealed apparatus [–1] continuous connection to and from condenser [–1] – penalise once [4]

(c) moles nitrobenzene = 7/123 = 0.057 moles (90%) 100% = 0.063 moles Moles benzene = 0.063 Mass benzene = 0.063 × 78 = 4.91 g Vol = mass/density = 4.91/0.88 = 5.58 cm3 [4]

(d) Place in separating funnel [1] Add sodium carbonate/hydrogencarbonate solution [1] Stopper, invert (and shake) Open tap (to release pressure) [1] Run off (lower) layer [1] [4]

Quality of written communication [2] (e) (i)

[2]

(ii) potassium iodide, aqueous [1] allow to warm up/heat/reflux [1] [2] 20

Total 50

+N N

6

MARKSCHEME


9569.01 F


2015


assessing

Module 3: Practical ExaminationPractical Booklet B

[AC234]

MONDAY 11 MAY, MORNING

29569.01 F

Annotation





General points







MARKING GUIDELINES





3

AVAILABLE MARKS

9569.01 F

1 (a) (i) 5Fe2+ + MnO4– + 8H+ → 4H2O + 5Fe3+ + Mn2+ [2]

(ii) pink [1]

(iii) MnO4– [1]

(iv) Performing a rough titration [1] adding dropwise before the endpoint [1] repeat for values within 0.1 cm3 [1] Any 2 from 3 [2] (b) Weigh (6.0g of) tablets on a balance In a beaker add (50 cm3) of deionised water to the tablets _`

a

Stir to dissolve Transfer with washings into a 250 cm3 volumetric flask _

`a Make up to the mark with deionised water/bottom of meniscus on line

(Stopper) and invert max [4]

(c) 22.4/1000 × 0.02 = 0.000448 Moles Fe2+ = 0.000448 × 5 = 0.00224 in 25 cm3

= 0.0224 in 250 cm3

RFM FeSO4.6H2O = 260 Mass FeSO4 = 0.0224 × 260 = 5.824g % = 5.824/6.00 × 100 = 97.07% [4]

(d) (i) blood red (solution) [1]

(ii) [Fe(H2O)6]3+ + SCN– → [Fe(H2O)5(SCN)]2+ + H2O [2] 17

4

AVAILABLE MARKS

9569.01 F

2 (a) (i) Based on the following observations, make deductions for salt A.

Test Deductions

1 Dissolve A in 20 cm3 of water

2 Add a few drops of concentrated ammonia solution to 2 cm3 of the solution of A in a test tube.

Confirms Fe3+/iron(III) hydroxide formed [1]/Fe(III)

3 Add 1 cm3 of barium chloride solution to 2 cm3 of the solution of A in a test tube, allow the mixture to settle.

Sulfate (ions) present [1]

(ii) Fe2(SO4)3 [1]

5

AVAILABLE MARKS

9569.01 F

(b) (i) Interpret the following data and identify the structural formula of the organic compound B, which has the empirical formula C2H4O.



Colourless liquid.

Pungent smell

2 Add 2 cm3 of deionised water to 2 cm3 of B in a test tube

One layer forms. B is miscible with water/completely soluble/–OH group present/can hydrogen bond (with water). [1]

3 Add 10 drops of B to 2 cm3 of acidifi ed potassium

dichromate solution in a test tube. Place the test tube in a hot water bath.

Solution stays orange.

Not an aldehyde or primary or secondary alcohol/ Possibly a tertiary alcohol/ketone/ carboxylic acid. [1]

4 Place 2 cm3 of B into a test tube. In a fume cupboard cautiously add a very small spatula measure of phosphorus(V) chloride to the test tube.

Fizzing.

Solid dissolves.

White fumes.

–OH present. –COOH present.

[1]

5 Place 5 cm3 of B in a boiling tube. Add 5 cm3 of ethanol, and then 1 cm3 of concentrated sulfuric acid. Heat the boiling tube in a water bath. Cautiously smell the contents of the boiling tube.

Sweet smell Ester (produced).–COOH present.

[1]

6 Add a spatula measure of sodium carbonate to 2 cm3 of B in a test tube.

Fizzing.

Solid dissolves.

CO2 released.

B is a carboxylic acid. [2]

(ii) Carboxylic acid(s) [1]

(iii)

CC

H H

C

H

H H

O

H O H

H

C

or

CH

H H

C

O

O H

H

C

C HH

H

[2]

(iv) +CH2COOH/CH2COOH+/C2H3O2+ [1] 13

6

AVAILABLE MARKS

9569.01 F

3 (a) Ammonia is a nucleophile [1]

(b) (i) Repeated boiling and condensing of a reaction mixture. [1]

(ii)Thermometer

Distillate/nitrobenzene

Heat

Condenser

Round-bottomed flask

Reaction mixture

no heat source [–1] no double jacket on condenser [–1] distillation fl ask open at top [–1] thermometer missing [–1], bulb not opposite side arm [–1] no labels [–1] If water in and out IS shown [–1] sealed apparatus [–1] continuous connection to and from condenser [–1] – penalise once [4]

(c) moles nitrobenzene = 7/123 = 0.057 moles (90%) 100% = 0.063 moles Moles benzene = 0.063 Mass benzene = 0.063 × 78 = 4.91 g Vol = mass/density = 4.91/0.88 = 5.58 cm3 [4]

(d) Place in separating funnel [1] Add sodium carbonate/hydrogencarbonate solution [1] Stopper, invert (and shake) Open tap (to release pressure) [1] Run off (lower) layer [1] [4]

Quality of written communication [2] (e) (i)

[2]

(ii) potassium iodide, aqueous [1] allow to warm up/heat/reflux [1] [2] 20

Total 50

+N N

6

chemistry...the total mark for this paper is 70. questions 1 and 2 are practical exercises each...

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