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2010 CHEM EXAM 1 2

SECTION A continued

N O W R I T I N G A L L O W E D I N T H I S A R E A

The following information refers to Questions 1 and 2.

The following titration curve was obtained by measuring the pH in a reaction ask during an acid-base titration.

0

2

4

6

8

10

12

14

20volume (mL)

pH

Question 1The graph represents the change in pH in the reaction ask whenA. a weak acid is added to a strong base.B. a weak base is added to a strong acid.C. a strong acid is added to a weak base.D. a strong base is added to a weak acid.

Question 2

Which one of the following is a suitable indicator for use in this titration?A. phenol red

B. thymol blueC. phenolphthaleinD. bromophenol blue

SECTION A Multiple-choice questions

Instructions for Section AAnswer all questions in pencil on the answer sheet provided for multiple-choice questions.Choose the response that is correct or that best answers the question.A correct answer scores 1, an incorrect answer scores 0.Marks will not be deducted for incorrect answers.

No marks will be given if more than one answer is completed for any question.

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3 2010 CHEM EXAM 1

SECTION A continuedTURN OVER


Question 3

A sample of the insecticide dichlorodiphenyltrichloroethane (DDT), C 14H9Cl 5, was found to contain 0.120 gof carbon.What mass of chlorine was present in the sample?A. 0.127 gB. 0.355 gC. 0.994 g

D. 1.01 g

Question 4

When 1.0 mole of Cu 3FeS 3 and 1.0 mole of O 2 are mixed and allowed to react according to the equation

2Cu 3FeS 3(s) + 7O 2(g) 6Cu(s) + 2FeO(s) + 6SO 2(g)

A. no reagent is in excess.

B. 5 mole of O 2 is in excess.

C. 57

mole of Cu 3FeS 3 is in excess.

D. 27

mole of Cu 3FeS 3 is in excess.

Question 5One possible reaction that occurs when trinitrotoluene (TNT), C 7H5 N3O6, explodes is

2C7H5 N3O6(s) 2C(s) + 12CO(g) + 5H 2(g) + 3N 2(g)

When one mole of TNT explodes the total volume of the gases produced from this reaction, measured at 27 C and

1.00 10 2 kPa, is closest toA. 0.249 LB. 22.7 LC. 249 LD. 274 L

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2010 CHEM EXAM 1 4

SECTION A continued


Question 6

Consider the following TLC plate of compounds X, Y and Z developed using a suitable mobile phase on a polarstationary phase.

solvent front

origin

X Y Z

3.202.75

2.151.70

0.80

0.00scale (cm)

The R f value of the most polar component in this TLC separation isA. 0.29B. 0.62C. 0.78D. 0.80

Question 7

Which of the following would be the most suitable analytical technique to determine the ratio of 235U to 238U in asample of uranium metal?A. mass spectroscopyB. gas liquid chromatographyC. atomic absorption spectroscopyD. nuclear magnetic resonance spectroscopy

Question 8

When a sample absorbs infrared radiationA. covalent bonds are broken.B. covalent bonds stretch and vibrate.C. the spin alignment of certain nuclei changes.D. electrons in atoms move to higher energy levels.

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5 2010 CHEM EXAM 1



Question 9

The graph shows the absorption spectra of three food dyes: Blue No. 1, Red No. 2 and Yellow No. 4.

0

0.2

0.4

0.6

0.8

1.0

400 500 600 700wavelength (nm)

Yellow No. 4 Red No. 2

Blue No. 1

absorbance

Which one of the following is the best wavelength to determine the concentration of Red No. 2 dye in a solutioncontaining a mixture of all three dyes?A. 430 nmB. 500 nmC. 540 nmD. 620 nm

Question 10

What is the correct systematic name for the following compound?

H3C CH CH CH 3

CH 2 CH 3

CH 2 CH 3

A. 2-ethyl-3-methylpentaneB. 3-methyl-4-ethylpentaneC. 3,4-dimethylhexaneD. 2,3-diethylbutane

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2010 CHEM EXAM 1 6

SECTION A continued


Question 11

For which one of the following molecular formulas is there only one possible structure?A. C2HCl 3B. C2H4Cl2C. C2H2Cl2D. C4H9OH

Question 12An organic compound reacts with both dilute hydrochloric acid and dilute sodium hydroxide solution.The compound could beA. C3H7ClB. C3H7 NH 2C. C4H9COOHD. H2 NCH 2COOH

Question 13

Which one of the following organic reactions does not result in the product shown on the right-hand side of the reaction?

A.

H C

H

H

H

H

H

H

H

H

CC

C ClH C

H

H

H

H

H

H

H

H

CC

C OH

H

HHC

NaOH

B.

H C

H

H

H

H

HH

HC C C

H

H

HCl

C.O

CC

OH+

D.

H C

H

H

H

H

H

CC H C

H

H

O

H

H

H

CC H

H2O, H+

H C

H

H

H

H

H

CH 3OH +

O

CO

H

H C

H

H

H

H

CC

C

HH

ClH

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7 2010 CHEM EXAM 1



Question 14

The side chains of some amino acids are able to form amide (peptide) bonds. Glutathione is a tripeptide that protectscells in humans by acting as an antioxidant. The structure of glutathione is

H2 N C CH 2 CH 2 C C C C N CH 2

OH

C

SH

CH 2O

The molecule of glutathione contains residues from the amino acids cysteine and glycine.The name of the third amino acid found in glutathione isA. asparagine.B. aspartic acid.C. glutamine.D. glutamic acid.

Questions 15 and 16 refer to the following information.The following diagram is a simpli ed illustration of the protein insulin. Insulin consists of 51 amino acids arranged intwo individual chains linked by disul de bridges.

S S

S

S

S

S

Question 15How many peptide links are present in one molecule of insulin?A. 48B. 49C. 50D. 51

Question 16

Disul de bridges are formed when the side chains of two amino acid residues react.The pair of amino acids that form the disul de bridges could beA. cysteine and serine.B. cysteine and glycine.C. cysteine and cysteine.D. cysteine and glutamic acid.

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2010 CHEM EXAM 1 8

SECTION A continued


Question 17

The following are incomplete and unbalanced equations representing three types of chemical reactions thatinvolve glucose. In reactions 1 and 3, product A is the same compound. In reactions 2 and 3, product B is the samecompound.

reaction 1 C 6H12O6(aq) C2H5OH(aq) + product Areaction 2 C 6H12O6(aq) C12H22O11(aq) + product Breaction 3 C 6H12O6(aq) product A + product B

Which one of the following correctly names reaction 3 and identi es product A and product B?

Reaction 3 Product A Product B

A. fermentation water carbon dioxide

B. fermentation carbon dioxide water

C. combustion water carbon dioxide

D. combustion carbon dioxide water

Question 18The structure of oxalic acid is shown below.

O

O

O

OH HC C

A 25.0 mL solution of oxalic acid reacts completely with 15.0 mL of 2.50 M NaOH.The concentration of the oxalic acid solution is

A. 0.667 MB. 0.750 MC. 1.33 MD. 1.50 M

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9 2010 CHEM EXAM 1


Question 19

The structure of Tami u, an anti u drug, is shown below.

CH 3

CO

OCH

CH 2H3C

CH3C

NH

NH 2

COO

CH 2H3C

I

II

III

H

H

The names of the functional groups labelled I, II and III are

I II III

A. amide amino carboxylic acid

B. amino amide ester

C. amide amino ester

D. amino amide carboxylic acid

Question 20

Copolymers are obtained when two or more different monomers are allowed to polymerise together.Part of a copolymer chain is shown below.

CH 3

C

H

CH 3

C

H

H

C

H

CH 3

C

H

CH 3

C

H

CH 3

C

H

CH 3

C

H

H

C

H

CH 3

C

H

CH 3

C

H

CH 3

C

H

The two alkenes that could react together to form this polymer areA. propene and but-1-ene.B. propene and but-2-ene.C. but-1-ene and but-2-ene.D. pent-2-ene and but-2-ene.

END OF SECTION ATURN OVER

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2010 CHEM EXAM 1 10


Question 1

The amount of iron in a newly developed, heat-resistant aluminium alloy is to be determined.An 80.50 g sample of alloy is dissolved in concentrated hydrochloric acid and the iron atoms are converted to Fe 2+(aq)ions.This solution is accurately transferred to a 250.0 mL volumetric ask and made up to the mark.

20.00 mL aliquots of this solution are then titrated against a standard 0.0400 M potassium permanganate solution.

5Fe 2+(aq) + MnO 4 (aq) + 8H +(aq) 5Fe 3+(aq) + Mn 2+(aq) + 4H 2O(l)

Four titrations were carried out and the volumes of potassium permanganate solution used were recorded in the table below.

Titration number 1 2 3 4

Volume of KMnO 4 (mL) 22.03 20.25 21.97 21.99

a. Write a balanced half-equation, including states, for the conversion of MnO 4

ions, in an acidic solution,to Mn 2+ ions.

2 marks

b. Calculate the average volume, in mL, of the concordant titres of the potassium permanganate solution.

1 mark

SECTION B Short answer questions

Instructions for Section BAnswer all questions in the spaces provided in blue or black pen or pencil.To obtain full marks for your responses you should give simpli ed answers with an appropriate number of signi cant gures to all numerical questions; unsimpli ed

answers will not be given full marks.

show all working in your answers to numerical questions. No credit will be given for an incorrect answer unlessit is accompanied by details of the working.

make sure chemical equations are balanced and that the formulas for individual substances include an indicationof state; for example, H 2(g); NaCl(s)

SECTION B Question 1 continued

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11 2010 CHEM EXAM 1


SECTION B continuedTURN OVER

c. Use your answer to part b. to calculate the amount, in mol, of MnO 4 (aq) ions used in this titration.

1 mark

d. Calculate the amount, in mol, of Fe 2+(aq) ions present in the 250.0 mL volumetric ask.

2 marks

e. Calculate the percentage, by mass, of iron in the 80.50 g sample of alloy. Express your answer to the correct numberof signi cant gures.

3 marks

Total 9 marks

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2010 CHEM EXAM 1 12



Question 2

The molecular formula of an unknown compound, X, is C 3H6O2.The infrared 13C NMR and 1H NMR spectra of this compound are shown below.

0.8

0.4A

infrared spectrum

3000 2000 1000wave number (cm 1)

transmittance

13C NMR

160 140 120 100 80 60

TMScalibration

peak

40 20 0 ppm

1H NMR

8910 7 6 5 4 3 2

TMScalibration

peak

1 0 ppm

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13 2010 CHEM EXAM 1



The 1H NMR spectrum data is summarised in the following table.

Chemical shift (ppm) Relative peak area Peak splitting

1.3 3 triplet (3)

4.2 2 quartet (4)

9.0 1 singlet (1)

a. Using the Infrared absorption data on page 7 of the Data Book, identify the atoms and the bonds between themthat are associated with the absorption labelled A on the infrared spectrum.

1 mark

b. How many different carbon environments are present in compound X?

1 mark

c. How many different hydrogen environments are present in compound X?

1 mark

d. i. The signal at 1.3 ppm is split into a triplet. What is the number of equivalent protons bonded to the adjacentcarbon atom?

ii. Draw the grouping of atoms that would give rise to the triplet and quartet splitting patterns.

1 + 1 = 2 marks

e. A chemical test showed that compound X does not react with a base. Propose a structure for compound X that is consistent with all the evidence provided.

2 marks

Total 7 marks

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2010 CHEM EXAM 1 14


SECTION B continued

Question 3

The molecules ethanol and nitrogen dioxide have the same molar mass (M = 46 g mol 1). They can be easily distinguished by mass spectrometry.The mass spectra of the two molecules are shown below.

100

80

60

40

20

010 20 30 40 50

relativeabundance

relativeabundance

mass spectrum

m/z

100

80

60

40

20

010 20 30 40 50

mass spectrum

m/z

Spectrum A

Spectrum

a. Write an equation showing how either an ethanol molecule or a nitrogen dioxide molecule becomes ionised in themass spectrometer.

1 mark

b. Which mass spectrum cannot be that of nitrogen dioxide? What evidence does the mass spectrum provide tosupport your answer?

2 marks

c. What is the formula of the species that produces the peak seen at m/z 30 in spectrum B?

1 mark

Total 4 marks

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15 2010 CHEM EXAM 1



Question 4

A single strand of DNA consists of a long chain of monomers called nucleotides. The structure of one of these nucleotidesof DNA is shown below.Each nucleotide will polymerise with other nucleotides to form a single strand of DNA.Part of this nucleotide will also form bonds with a complementary nucleotide on a parallel strand of DNA forming thedouble helix structure.

H3CO

NH

O N

O

O

O

OH

P

OH

CH 2O

A

D

BE

F

C

a. Circle only the letters which represent the sites where this nucleotide can form bonds with other nucleotides toform a single strand of DNA.

A B C D E F

2 marks

b. i. Name the type of bonding that holds the two strands in human DNA together.

ii. Circle only the letters that represent the locations where these bonds between the two strands of DNA areformed.

A B C D E F1 + 2 = 3 marks

Total 5 marks

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2010 CHEM EXAM 1 16



Question 5

A forensic chemist wants to test the accuracy of a gas chromatograph that is to be used for the analysis of blood alcoholcontent.A blood sample may contain a number of volatile chemicals that can interfere with the identi cation and measurementof ethanol in the blood. A sample containing a mixture of ethanol and several other volatile chemicals was injected intothe gas chromatograph. The following chromatogram was obtained.

m e t

h a n o l

a c e t a l

d e h y d e

e t h a n o

l

p r o p a n - 2 - o

l

a c e t o n e

p r o p a n -

1 - o l

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4

20

40

60

80

100

retention time (minutes)

recorder response

a. The forensic chemist claims that the presence of these volatile chemicals would not affect the qualitative analysisof ethanol.

i. What evidence is presented in the chromatogram to support this claim?

ii. To determine the percentage of alcohol in a blood sample only the peak at a retention time of 0.9 minutes ismeasured. Explain why.

1 + 1 = 2 marks

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17 2010 CHEM EXAM 1



The following calibration graph was constructed using simulated standard blood alcohol samples ranging in concentrationfrom 0.000% to 0.400% m/v ethanol. Each standard was run through the chromatography column and the area underthe peak produced at a retention time of 0.9 minutes was measured.

250 000

200 000

150 000

100 000

50 000

00.000 0.100 0.200 0.300 0.400 0.500

% ethanol (m/v)

peak area

The blood alcohol content of a car driver was determined using this chromatographic technique.b. Determine the percentage (m/v) of alcohol in the drivers blood if the peak area at a retention time of 0.9 minutes

was found to be 110 000.

1 mark

Total 3 marks

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2010 CHEM EXAM 1 18



Question 6

Enzymes are complex protein structures that function as biological catalysts.a. Why does a particular enzyme generally only catalyse a speci c reaction?

1 mark

Invertase is an enzyme which catalyses the conversion of sucrose to glucose and fructose. Invertase has a maximumactivity temperature different from many other enzymes. The graph below shows the results of a study into the effectsof both pH and temperature on the activity of invertase in sucrose solution.

35 C45 C55 C65 C

activity of invertase vs pH at different temperatures (C)

2 3 4 5 6 7 80

50100150200250300350400450

pH

activity(mmol glucose/

mg invertase)in 30 minutes

temperature

b. At what temperature and pH does the enzyme in the study have maximum activity?

Temperature __________ pH __________ 2 marks

c. Why does changing the pH from the optimum value cause a decrease in the activity of the enzyme?

1 mark

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19 2010 CHEM EXAM 1



d. In this study the activity of the enzyme was measured as the number of millimole of glucose produced per milligramof enzyme (mmol glucose/mg invertase) in 30 minutes.

Assuming excess sucrose, calculate the mass of glucose (M r = 180) produced in 30 minutes from a sucrose solutioncontaining 1.00 10 4 g of invertase if the measured activity is 300 mmol glucose/mg invertase.

2 marks

Total 6 marks

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2010 CHEM EXAM 1 20



Question 7

a. Biodiesel is an alternative to standard diesel fuel. Biodiesel is made from biological ingredients instead of petroleum.Biodiesel is usually made from plant oils or animal fats through a series of chemical reactions.

In one process a common triglyceride in palm oil, known as POP, is reacted with methanol in the presence of potassium hydroxide as a catalyst. The result is a mixture of methyl esters of the fatty acids (biodiesel).

i. The value of the stoichiometric rationumber of moles of methanol

number of moles of POP is

ii. Calculate the volume, in litres, of methanol (density = 0.79 g mL 1) required to react completely with 10.0 kgof the triglyceride POP (M r = 833) to produce glycerol and the mixture of methyl esters.

1 + 3 = 4 marks

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21 2010 CHEM EXAM 1



b. Cervonic acid is a polyunsaturated fatty acid found in sh oil. The number of carbon-carbon double bonds in amolecule of cervonic acid can be determined by titration with iodine, I 2, solution. An addition reaction takes place

between the double bonds in cervonic acid and iodine. 20.00 mL of 0.300 M I 2 solution reacted exactly with 0.328 g of cervonic acid. The molar mass of cervonic acid

is 328.0 g mol 1 . i. Calculate the number of double bonds in a molecule of cervonic acid.

There are 22 carbon atoms in a molecule of cervonic acid. ii. What is the formula of cervonic acid?

3 + 1 = 4 marks

Total 8 marks

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23 2010 CHEM EXAM 1



e. Aspirin reacts with a strong base according to the equation

COH

O

C CH 3

+ OH (aq) H2O(l) + product B

Draw the structure of product B.

1 mark

Total 7 marks

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2010 CHEM EXAM 1 24


Question 9

The boiling points of several alkanols are provided in the following table.

Alkanol methanol ethanol propan-1-ol butan-1-ol pentan-1-ol

Boiling point (C) 64.5 78.3 97.2 117.2 138.0

A mixture of two of these alkanols is to be separated in an experiment using fractional distillation. The mixture is placed

into the distillation apparatus at room temperature and then gently heated. The rst fraction is collected at 97.2 C.a. i. Identify one alkanol that could not be present in this mixture.

ii. By speci cally referring to this experiment, explain why the alkanol identi ed in part i. could not be present.

1 + 1 = 2 marks

b. Provide one reason why the distillation ask should not be heated using a bunsen burner.

1 mark

c. Butane and propan-1-ol have similar molar masses. The boiling point of butane is 138.4 C and that of propan-1-ol is 97.2 C. Explain, in terms of intermolecular forces, the difference between the boiling points ofthese two compounds.

3 marks

Total 6 marks

END OF QUESTION AND ANSWER BOOK

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SECTION A


Question 1

least A. B. C. D.

Question 2

2 A.

H C C C C

H H H H

Cl Cl H H

H

B.

H C C C C

H H H H

H Cl Cl HH

C.

H C C C C

H Cl H H

H Cl H H

H

D.

Cl C C C C

H H H H

H H H H

Cl


Instructions for Section Aall correct best answers

not

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SECTION A TURN OVER


Question 3

H3C C CH 2 CH CH 3

CH 3 CH 3

CH 3

H3C CH CH 2 C CH 3

CH 3

CH 3 CH 3

H3C CH CH 2 CH 2 C H

CH 3

CH 3 CH 3

I

II

III

IV

C CH 2 CH 2 CH CH 3

CH 3 CH 3

CH 3

H

A. B. C. D.

Question 4 not

A. B. C. D.

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SECTION A


Question 5

Leu

Cys

Val

Val

ValVal

Asp

Asp

Asp

Asp

Val His Tyr

Tyr

Leu

Leu

Tyr

Leu

Cys

Val

Cys

Tyr

Ser

His

AspAlaSer Cys

CysCys

AspTyr Ala

Ser

Asp

Ala

Ala

Val

His

His

Cys

X

Y

Y

X Y

A. B.

C.

D.

Question 6

A.

B. C. D.

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SECTION A TURN OVER


Question 7

Cl

Cl

Cl Cl

H

C C

F

F H

F HC C

HFSbCl 2130 C

ClF

F Br

F HC C450 C

step 1 step 2molecule X

Br 2

Type of reaction in step 2 Systematic name of molecule X

A.

B.

C.

D.

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SECTION A


Question 8

more

H3C

CH 3

CH 2CH C O

CH 3CH

H

C C NH

H

O

OH(CH

2)4

NH 2

+ ibuprofen lysine

ibuprofen lysine

OH

H

H3 N (CH 2)4 C

NH2

+D.

O

B.

A.

C.

CH 3 C N

O H

(CH 2)4C

H NH 2

OH

CO

CH3

CH 2CH

CH 3CH

H

C NH 2

(CH 2)4

NH 2

CH 3 C O

O

C

OCH 3

CH 2CH

CH 3CH

CH 3 C

OCH 3

CH 2CH

CH 3CH

OH

H

H

C

(CH 2)4

NH 2

CH 3 C N

OCH 3

CH 2CH

CH 3CH

C

OH

O

C O

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SECTION A TURN OVER


Question 9

layer A

layer B

A.

B. C. D.

Question 10

Step 1 3 2 2

Step 2 3 2 2 3 2

Step 3 3 3 3 2 2 2

Step 4 3 2 2 2 3

A. B. C. D.

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SECTION A TURN OVER


Question 13

2

loss

A. 2 2

B. 2 1

2 2 2

C. 2 2 2

D. 2 3

2 2 2

Question 14

A. B. 2C. 2D.

2

Question 15

3 3

3 3 2 2 2

3

A. B. C. D.

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SECTION A


Question 16

A.

B.

C.

D.

Question 17

final solvent level

origin

samplesW Z

A. B. C. D.

Question 18

A. B. C. D.

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Question 19

A. B. C.

D.

Question 20

A. B. C. D.


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SECTION B Question 1

Question 1

A.

C

O

O

O

H

H

B.

OCH 2OH

H

OH

OH

OHHO

H

H

HH

C.

OHOCH 2 OH

H

H

HH H

OH

D.

C13H27 CO

O H

E.

H

CH OH

H OH

H OH

C

C

H

F.

C17H31 CO

O CH 3

G.

C17H29 CO

O H

H.

OCH 2OH

OO O

OH

OH

OCH 2OH

OH

OH

OCH 2OH

OH

OH O

H

H

H H H

H H HH H

H

H H

H

H


Instructions for Section Ball

2

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Question 2

a. 79 2 5

100

80

60

40

20

0

relativeabundance

0 20 40 60 80 100 120

108 110

m/z

i.

ii. 79

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SECTION B TURN OVER

b. 2 2 one

11 10 9 8 7 6 5 4 3 2 1 0 ppm

TMS

i. 2 2

Structure 1 Structure 2

ii.

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Question 3

0123456789

1011121314151617181920

0 50 100 150 200caffeine concentration (ppm)

peak area(1000)

Peak area of caffeine standard solutions: retention time = 96 seconds

25

Sample Retention time ofmajor peak (seconds)

Peak area of largestpeak

32 8 500

a.

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SECTION B Question 3 TURN OVER

10 20 30 40 50 60 70 80 90 100 110 120time (s)

standard (50 ppm)20

15

105

10 20 30 40 50 60 70 80 90 100 110 120time (s)

20

15

10

5

10 20 30 40 50 60 70 80 90 100 110 120time (s)

20

15

10

5

10 20 30 40 50 60 70 80 90 100 110 120time (s)

20

15

10

5

soft drink A

soft drink B

espressocoffee

peak area(1000)

peak area(1000)

peak area(1000)

peak area(1000)

Chromatograms of 50 ppm standard caffeine solution,soft drink A, soft drink B and espresso coffee

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SECTION B

b.

c. i.

ii.

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SECTION B TURN OVER

Question 4

2 5

2 3

2 2

a. 2 5 2

2 5

b. 2

2 2

2 5 part a.

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Question 5

2

2 2 2 72

a. 2 72

2 72 2

i. 2

ii.

2 2 72 2 2

2 2 7 2

2 72

3 2

2 72 2

b. i.

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SECTION B TURN OVER

ii.

iii.

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SECTION B

Question 6

a. i.

G A T A

ii.

H2 N

N

N N

N

O

O

P

O HO

OH

O

H HH H

H

CH 2

b.

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23


SECTION B Question 7 TURN OVER

Question 7

3 2 2 3 2

a.

ClCH 2CH 2CH(CH 3)2 compound C

reaction I reagent A reaction II Cr 2O72 /H+

compound B CH 3COOH

reaction III reagent D

CH 3COOCH 2CH 2CH(CH 3)2

(banana oil, 3-methylbutylethanoate)

i

ii.

iii.

iv.

v.

vi.

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SECTION B

b.

0.8

0.6

0.4

0.2

transmittance

3000 2000 1000wavenumber (cm 1)

infrared spectrum of compound Bwavenumber (cm 1)

infrared spectrum of the banana oilobtained after distillation

infrared spectrum infrared spectrum

0.8

0.6

0.4

0.2

transmittance

3000 2000 1000

c.

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25


Question 8

N

H

C

H

C

O

N

H

C

H

C

O

OHCH 2CH 2

a. diagram I

b.

c.

END OF QUESTION AND ANSWER BOOK

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2012 CHEM EXAM 1 2

SECTION A continued

Question 1

H C

H

H

C

H

H

C

H

H

C

Cl

C

H

C

H

H

H

The correct systematic name for the compound shown above isA. 2-chlorohex-2-eneB. 3-chlorohex-2-eneC. 3-chlorohex-3-eneD. 4-chlorohex-5-ene

Question 2The number of structural isomers of C 4H9Cl isA. 2B. 3C. 4D. 5


Instructions for Section A

Answer all questions in pencil on the answer sheet provided for multiple-choice questions.Choose the response that is correct or that best answers the question.A correct answer scores 1, an incorrect answer scores 0.Marks will not be deducted for incorrect answers.

No marks will be given if more than one answer is completed for any question.

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3 2012 CHEM EXAM 1


Question 3The following diagram is a simpli ed representation of a section of DNA.

X

Y

The main types of bonds at X and Y are

X Y

A. ionic bonds hydrogen bonds

B. covalent bonds dispersion forces

C. dispersion forces ionic bonds

D. covalent bonds hydrogen bonds

Question 4In a double-stranded DNA sample, adenine constitutes 16% of the total number of bases.The percentage of guanine content in the double strand isA. 16%B. 34%C. 42%D. 68%

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5 2012 CHEM EXAM 1


Question 8In the laboratory, salicylic acid can be used to produce two different compounds as shown in the diagram below.These compounds are key components of pharmaceutical products.

H

H

H

HH

CC

C O HC

C

C

O

O H

C

H 3 C

OO

O CH 3

reaction 1

reagent X

reaction 2

compound Y

H

H

H

HH

CC

C O CH 3C

C

C

O

O H

C

H 2 O+

H

H

H

HH

CC

C O HC

C

C

O

O

O

C

C

CH 3 COOH

CH 3

+C C

Which one of the following correctly identi es reagent X and compound Y?

reagent X compound Y

A. methanol methyl salicylate

B. methanoic acid methyl salicylate

C. methanoic acid acetylsalicylic acid (aspirin)

D. methanol acetylsalicylic acid (aspirin)

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2012 CHEM EXAM 1 6

SECTION A continued

Use the following information to answer Questions 911.

H C

H

H

H

H

H

H

H

HC C

O

O C C H

Question 9Which one of the following is the correct systematic name of this compound?A. ethyl propanoateB. ethyl ethanoateC. propyl ethanoateD. propyl pentanoate

Question 10The species that produces the molecular ion peak in the mass spectrum of this compound isA. [CH 3CH 2COOCH 2CH 3]

+

B. [CH 3CH 2COOCH 2CH 3]2+

C. [CH 3CH 2COOCH 2CH 3]

D. CH 3CH 2COOCH 2CH 3

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7 2012 CHEM EXAM 1


Question 11

Which one of the following infrared (IR) spectra is consistent with the structure of this compound?

Due to copyright restriction,this material is not supplied.

Source: Spectral Database for Organic Compounds SDBS

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2012 CHEM EXAM 1 8

SECTION A continued

Question 12The following chromatogram was produced when 0.1 g of decane was passed through a gas chromatographycolumn.

20 000

10 000

detector response

5 10 15 20retention time (min)

The chromatogram produced when 0.2 g of decane is passed through the same column under identical conditions is best represented byA.

20 000

10 000

5 10retention time (min)

15 20

detector response

B.

20 000

10 000


15 20

detector response

C.

20 000

10 000


15 20

detector response

D.

20 000

10 000


15 20

detector response

Question 1315.0 mL of 10.0 M HCl is added to 60.0 mL of deionised water.The concentration of the diluted acid isA. 3.33 MB. 2.50 MC. 2.00 MD. 0.500 M

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9 2012 CHEM EXAM 1


Question 14A desalination plant produces 200 gigalitres (GL) of fresh water each year. The maximum level of boron permitted indesalinated water is 0.5 ppm (0.5 mg L 1). The maximum mass, in kilograms, of boron that is permitted in one years

production of desalinated water isA. 9.26 10 3

B. 1.0 10 5

C. 1.08 10 6

D. 1.0 10 8

Question 15A sample of the anticancer drug Taxol , C 47H51 NO 14 , contains 0.157 g of carbon.The mass, in grams, of oxygen in the sample isA. 0.0468B. 0.0624C. 0.209D. 0.703

Question 16A helium balloon is in ated to a volume of 5.65 L and a pressure of 10.2 atm at a temperature of 25 C.The amount of helium, in moles, in the balloon isA. 0.023B. 0.276C. 2.36D. 27.95

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2012 CHEM EXAM 1 10

SECTION A continued

Question 17Which titration curve best represents the change in pH as 0.100 M NaOH solution is added to a 10.0 mL aliquot of0.100 M HCl solution?

A.

141210

86420

0 0.005 0.010 0.015 0.020

pH

volume, in litres, of NaOH added

B.

141210

86420

0 0.005 0.010 0.015 0.020

pH


C.

14

1210

86420

0 0.005 0.010 0.015 0.020

pH


D.

14

1210

86420

0 0.005 0.010 0.015 0.020

pH


Question 182.1 g of an alkene that contains only one double bond per molecule reacted completely with 8.0 g of bromine, Br 2.The molar mass of bromine, Br 2, is 160 g mol 1.Which one of the following is the molecular formula of the alkene?A. C5H10B. C4H8C. C3H6D. C2H4

Question 19The oxidation state of phosphorus in the pyrophosphate ion P 2O7

4 isA. +3.5B. +5C. +7D. +10

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11 2012 CHEM EXAM 1

Question 20Consider the following reaction.

IO3 (aq) + 5I (aq) + 6H +(aq) 3I2(s) + 3H 2O(l)

The correct half equation for the reduction reaction isA. 2I (aq) I2(s) + 2e

B. 2H +(aq) + 2e H2O(l)

C. IO 3 (aq) + I (aq) I2(s) + 3O 2 (aq) + 4e

D. 2IO 3 (aq) + 12H +(aq) + 10e I2(s) + 6H 2O(l)


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2012 CHEM EXAM 1 12


Question 1a. The cellulose that is present in plant matter cannot be directly fermented to produce bioethanol. The cellulose

polymer must rst be broken down into its constituent monomers. A section of cellulose polymer is shown below.

H

H

H

H HOH

OHH

CH 2 OH

CH 2 OH

OO

O

OH

OH

H

H

H

H

OO

H

H

H

H HOH

OHH

CH 2 OH

CH 2 OH

OO OH

OH

H

H

H

H

OO

i. What is the name of the monomer from which cellulose is formed?

ii. Complete the following chemical equation to show the formation of ethanol by fermentation of thecellulose monomer.

C6H12O6 (aq) +

iii. Ethanol can be manufactured directly from ethene gas in the presence of a catalyst. Write a balancedequation for this reaction.

1 + 1 + 1 = 3 marks


Instructions for Section B

Answer all questions in the spaces provided. Write using black or blue pen.To obtain full marks for your responses you should give simpli ed answers with an appropriate number of signi cant gures to all numerical questions;

unsimpli ed answers will not be given full marks. show all working in your answers to numerical questions. No credit will be given for an incorrect answer

unless it is accompanied by details of the working. make sure chemical equations are balanced and that the formulas for individual substances include an

indication of state; for example, H 2(g); NaCl(s).

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13 2012 CHEM EXAM 1


b. Triglycerides are an important source of energy in the body. During digestion, triglycerides are broken downin the small intestine by the enzyme lipase. An incomplete chemical equation that shows the hydrolysis of atriglyceride is shown below.

H

C

C

C

O

O

O

H

H

H

H

O

C

C

C

O

C

(CH 2)16CH 3

(CH 2)16CH 3 + 3H 2O

(CH 2)16CH 3

CH 3(CH 2)16COOH

product A product B

+ C3H8O3

i. In the spaces provided above, balance the equation by adding appropriate coef cients for product A and product B.

ii. Name the fatty acid that is produced by the hydrolysis of this triglyceride.

iii. The fatty acid produced in the above reaction is completely oxidised to produce carbon dioxide and water.Write a balanced equation for the oxidation reaction.

1 + 1 + 2 = 4 marks

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2012 CHEM EXAM 1 14


Question 2A drop that contains a mixture of four amino acids was applied to a thin layer chromatography plate. The plate was

placed in solvent G and the following chromatogram was obtained.

spot 1

solvent front: solvent G

B C

A Dapplication

point of drop

chromatogram I

The R f values for each of the amino acids in solvent G are provided in Table 1 below.

Table 1. R f values in solvent G

amino acid R f (solvent G)

alanine 0.51

arginine 0.16

threonine 0.51

tyrosine 0.68

a. Name the amino acid that corresponds to spot 1.

1 mark

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15 2012 CHEM EXAM 1


The plate was dried, rotated through 90 in an anticlockwise direction and then placed in solvent F. The R f values foreach of the amino acids in solvent F are provided in Table 2 below.

Table 2. R f values in solvent F

amino acid R f (solvent F)

alanine 0.21

arginine 0.21

threonine 0.34

tyrosine 0.43

The following chromatogram was obtained.

C D

B A

chromatogram II

solvent front: solvent F

solvent front:solvent G

application point of drop

b. Circle the spot on chromatogram II that represents alanine.1 mark

c. Explain, in terms of the data provided, why only three spots are present in chromatogram I while four spots are present in chromatogram II.

2 marks

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2012 CHEM EXAM 1 16


Question 3Sections of the primary structure of nylon and the primary structure of a protein are shown below.

C

O

(CH 2)4 C

O

C

O

N

H

(CH 2)6 (CH 2)4 (CH 2)4(CH 2)6C

O

N C

O

C

O

H

N

H

N

H

nylon

O

N

H

C N

O O O O

C N CH 2 C CH2 C N C NCH(CH 3) CH(CH 3)CH 2

H H H H

protein

Nylon is composed of two monomers. The structure of one of the monomers is provided below.

O

HH O O

C

O

C(CH 2)4

a. Draw the structure of the other monomer.

1 mark

b. Name the functional groups that link the monomers in

nylon.

protein.2 marks

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17 2012 CHEM EXAM 1


c. Look carefully at the functional group that links monomers in protein and nylon. The functional groups thatconnect the protein monomers are oriented in the same direction. The functional groups that link the nylonmonomers are oriented in opposing directions.

Explain why the functional groups that link the monomers in protein are oriented differently from the functionalgroups that link the monomers in nylon. Make appropriate reference to the structures of nylon and proteinmonomers in your answer.

2 marks

d. Perspex (polymethyl methacrylate) is a clear, colourless polymer used for optical applications. The structural

formula of the only monomer used in the synthesis of perspex, methyl methacrylate, is shown below.

H 2 CC

C

CH 3

CH 3O

O

Draw a section of the polymer showing at least two units of the monomer.

2 marks

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2012 CHEM EXAM 1 18

SECTION B continued

Question 4a. Give the systematic names of the alkanol and the carboxylic acid that are required to synthesise propyl

propanoate.

2 marks

b. Write a balanced chemical equation for the synthesis of propyl propanoate. Use the semi-structural formula for

the reactants and products.

2 marks

c. Describe the steps that are required to prepare a sample of pure propyl propanoate using only a pure sample ofthe alkanol as the starting reagent. Include any reagents that are used in the synthesis. An annotated ow chartmay be used in your answer.

3 marks

d. Identify one method that could be used to verify that the substance produced is pure propyl propanoate. Explainhow this method would indicate that the product is pure propyl propanoate.

2 marks

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2012 CHEM EXAM 1 20


Question 5An organic chemist found a bottle in the laboratory that was labelled organic cleaning uid, C 3H8O. She decided totest the liquid. The chemist obtained the following data about the compound in the cleaning uid: the 1H NMR and13C NMR spectra, and the infrared spectrum.The 1H NMR data is summarised in the table below.

Chemical shift (ppm) Relative peak area Peak splitting

1.2 6 doublet (2)

2.2 1 singlet (1)

3.6 1 septet (7)

6 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0

TMSsignal

TMSsignal

chemical shift (ppm)

1H NMR spectrum

chemical shift (ppm)

70 60 50 40 30 20 10 0

13C NMR spectrum

a. i. How many different carbon environments are present in the compound?

ii. How many different hydrogen environments are present in the compound?

iii. In the 1H NMR spectrum, the signal at 3.6 ppm is split into a septet (7 peaks). What is the number ofequivalent protons that are bonded to the adjacent carbon atom(s)?

1 + 1 + 1 = 3 marks

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21 2012 CHEM EXAM 1


Infrared spectrum

3500 3000 2500 2000 1500 1000 500

absorption

wavenumber (cm 1)A

b. Using the Infrared absorption data on page 7 of the Data Book, identify the atoms that are associated with theabsorption labelled A on the infrared spectrum.

1 mark

c. Draw a structure of the compound in the cleaning uid that is consistent with the NMR and IR data.

1 mark

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2012 CHEM EXAM 1 22


Question 6The iron content in multivitamin tablets was determined using atomic absorption spectroscopy.The absorbances of four standards were measured.Three multivitamin tablets were selected. Each tablet was dissolved in 100.0 mL of water. The absorbance of each ofthe three solutions was then measured.The following absorbances were obtained.

Solution Concentrationmg/L

Absorbance

Standard 1 0.00 0.06

Standard 2 100.0 0.16

Standard 3 200.0 0.25

Standard 4 300.0 0.36

Standard 5 400.0 0.46

Tablet 1 0.39

Tablet 2 0.42

Tablet 3 0.45

a. i. Use the grid below to construct a calibration graph of the absorbances of the standard solutions.

0.8

0.6

0.4

0.2

100 200concentration (mg/L)

300 400

absorbance

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23 2012 CHEM EXAM 1


ii. Determine the average iron content, in milligrams, of the multivitamin tablets.

2 + 2 = 4 marks

Spectroscopic techniques work on the principle that, under certain conditions, atoms, molecules or ions will interactwith electromagnetic radiation. The type of interaction depends on the wavelength of the electromagnetic radiation.

b. Name one spectroscopic technique that you have studied this year.

i. Which part of the electromagnetic spectrum does this technique use?

ii. How does this part of the electromagnetic spectrum interact with matter? What information does thisspectroscopic technique provide?

1 + 2 = 3 marks

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2012 CHEM EXAM 1 24


Question 7Students in a chemistry class were required to design a procedure to determine gravimetrically the concentration oflead(II) ethanoate, Pb(CH 3COO) 2, in a sample of hair dye. They were instructed to measure the mass of precipitateformed when a sample of the hair dye was added to either 0.1 M potassium iodide or 0.1 M potassium nitrate.The students were also provided with the following data.

Name Formula Relative molar mass Solubility at 25 C (g/100 g)

lead(II) ethanoate Pb(CH 3COO) 2 325.3 55.0

lead(II) iodide PbI 2 461.0 0.076

lead(II) nitrate Pb(NO 3)2 331.2 60.0

Student A decided to precipitate the lead(II) ions in the hair dye as lead(II) iodide. She added an excess of 0.1 M KIsolution to 20.0 mL of hair dye. The yellow precipitate was ltered using pre-weighed lter paper. The precipitatewas then washed with distilled water. The precipitate and lter paper were gently heated, allowed to cool and thenweighed. This step was repeated several times.

Student As results are summarised below.

Volume of hair dye solution 20.0 mL

Mass of lter paper 0.3120 g

Mass of lter paper plus precipitate after rst heating 0.4831 g

Mass of lter paper plus precipitate after second heating 0.4059 g

Mass of lter paper plus precipitate after third heating 0.4059 g

Mass of lter paper plus precipitate after fourth heating 0.4059 g

a. i. Write a balanced equation for the precipitation of lead(II) iodide.

ii. Explain why the lter paper and precipitate were heated and weighed several times.

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25 2012 CHEM EXAM 1


iii. Calculate the mass, in grams, of lead(II) iodide formed.

iv. What is the mass, in grams, of lead(II) ethanoate that is present in 100.0 mL of hair dye solution?

1 + 1 + 1 + 3 = 6 marks

Student B decided to precipitate the lead(II) ions in the hair dye as lead(II) nitrate. However, he did not produce any precipitate.b. Explain why no precipitate of lead(II) nitrate formed.

1 mark

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2012 CHEM EXAM 1 26


Question 8The solubility of highly soluble, thermally unstable salts such as ammonium chloride may be determined by backtitration.In one experiment a 5.00 mL saturated solution of ammonium chloride, NH 4Cl, at 20.0 C, was diluted with distilledwater to 250.0 mL in a standard ask.A 20.0 mL aliquot of this solution was added to 10.0 mL of 0.400 M NaOH solution. The solution was heated todrive off the ammonia formed by this reaction.

When the ask had cooled, the excess hydroxide ions were neutralised by 14.7 mL of 0.125 M HCl solution. Themolar mass of ammonium chloride is 53.5 g mol 1.a. i. Write an equation for the neutralisation reaction.

ii. Determine the amount, in mole, of NaOH that was originally added to the ammonium chloride solution.

iii. Determine the amount, in mole, of ammonium chloride in the 20.0 mL aliquot.

iv. Calculate the amount, in mole, of ammonium chloride in 5.00 mL of the saturated solution.

v. Calculate the solubility, in gL 1 , of ammonium chloride in water at 20 C.

1 + 1 + 2 + 1 + 2 = 7 marks

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27 2012 CHEM EXAM 1

b. If the burette was rinsed with water instead of acid before the titration, how would the calculated solubility ofammonium chloride be affected? Explain your answer.

2 marks

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