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Paper Reference(s)

6243/01BSchools, Colleges, International Teaching Institutions and International Centres

Edexcel GCEChemistry

Advanced Subsidiary

Unit Test 3A: Practical TestFriday 18 May 2007 Morning

Time: 1 hour 45 minutes

Materials required for examination Items included with question papers

See Confidential Instructions (already Nilissued to centres) relating to this

practical test.

Candidates are allowed the use of textbooks and their own class notes duringthe practical test. Candidates may also use a calculator.

Instructions to Candidates

In the boxes above, write your centre number, candidate number, your surname, initial(s) andsignature.AnswerALL the questions. Write your answers in the spaces provided in this question paper.Show all the steps in any calculations and state the units.Final answers to calculations should be given to an appropriate number of significant figures.

Information for Candidates

The total mark for this paper is 50. The marks for individual questions and parts of questions areshown in round brackets: e.g. (2). There are 12 pages in this question paper. All blank pages areindicated.

Advice to CandidatesYou are reminded of the importance of clear English and careful presentation in your answers.You are reminded that you should take all usual safety precautions when working in achemistry laboratory.

Examiners use only

Team Leaders use only

Question LeaveNumber Blank

1

2

3

4

Total

Surname Initial(s)

Signature

Centre

No.

*N26025A0112*Turn over

Candidate

No.

Paper Reference

6 2 4 3 01B

This publication may be reproduced only in accordance with

Edexcel Limited copyright policy.

2007 Edexcel Limited.

Printers Log. No.

N26025AW850/R6243/57570 7/7/7/3/4900

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*N26025A0212*

Answer ALL the questions.

Write your answers in the spaces provided in this question paper.

1. You are provided with an inorganic compound L and an organic liquid M.

Carry out the following tests on L and M. Record, in the appropriate spaces, your

observations and your inferences about L orM.

(a) Carry out a flame test on L.

Observation Inference about L

(2)

(b) To 2 cm3 of water in a test tube, add 10 drops ofM and 5 drops of aqueous potassium

hydroxide. Stand the tube in a beaker of hot water for about two minutes.

Divide the resulting mixture equally between two more test tubes. Use one portion

for test (i) and keep one aside for test (iii).

(i) To one portion of reaction mixture, add 1 cm3 of dilute nitric acid followed

by 10 drops of aqueous silver nitrate. Finally add 5 cm3 of dilute aqueous

ammonia.

Observations Inference about M

The inorganic compound L and the organic liquid M contain one element in

common (which is neither carbon nor hydrogen).

State the formula of compound L.

(4)

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Turn over*N26025A0312*

(ii) Identify the functional group that is present after heating M with

potassium hydroxide solution.

................................................................................................................................

(1)

(iii) To the second portion of the reaction mixture, add 1 cm3 of aqueous sulphuric

acid and 10 drops of aqueous potassium dichromate(VI).

Replace the test tube into the beaker of hot water. Observe the contents after

about three minutes.

Observation

Inference about the product from

the reaction ofM with potassium

hydroxide

(2) Q1

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*N26025A0412*

2. You are provided with:

Solid sulphamic acid, NH2SO3H

Solution Y, dilute sodium hydroxide

Phenolphthalein indicator

You are required to prepare a standard solution of sulphamic acid and use it to determine

the concentration of the sodium hydroxide.

Sulphamic acid acts as an acid and reacts with sodium hydroxide according to the

following equation:

NH2SO3H + NaOH NH2SO3Na + H2O

(a) Preparation of standard solution

1. Weigh the stoppered tube containing the sulphamic acid. Record the mass in

Table 1.

2. Transfer the solid to a 250 cm3 beaker.

3. Reweigh the stoppered tube. Record this mass in Table 1. Calculate the mass

of solid sodium borate transferred.

4. Dissolve the solid in approximately 150 cm3 of distilled water. Using a funnel,

transfer the solution to a 250 cm3 volumetric flask. Rinse the beaker with distilled

water into the volumetric flask. Finally, rinse the funnel into the volumetric flask.

Make the solution up to the mark with distilled water. Stopper the flask, then

invert and shake it several times to ensure that the solution is thoroughly mixed.

Table 1

Mass of stoppered tube + sulphamic acid g

Mass of stoppered tube after transfer of

sulphamic acidg

Mass of sulphamic acid used g

(3)

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(b) Titration

1. Rinse the burette with solution Y, dilute sodium hydroxide, and then fill the

burette with solution Y.

2. Rinse out the pipette with the sulphamic acid solution. Transfer 25.0 cm3 of the

solution into a conical flask. Add 3 drops of phenolphthalein.

3. Titrate the solution with the sodium hydroxide until the end-point is reached.

4. Record your burette readings and titre in Table 2.

5. Repeat the procedure until you obtain two titres that differ by no more than

0.20 cm3. Record all your burette readings and titres in Table 2.

Table 2

Titration number 1 2 3 4 5

Burette reading

(final)/cm3

Burette reading

(initial)/cm3

Titre/cm3

List the numbers of the titrations that you will use to calculate the mean (or average)

titre.

Calculate the mean titre.

Write the value of the mean titre in the space below.

....................................cm3 of dilute sodium hydroxide, solution Y, reacts with 25.0 cm3 of

sulphamic acid solution.

(12)

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(c) Calculations

(i) Determine the molar mass of sulphamic acid, NH2SO3H, and hence calculate the

amount (moles) used to prepare the standard solution.

[Molar mass / g mol1: H = 1.0; N = 14.0; O =16.0; S = 32.0.]

(2)

(ii) Hence calculate the amount (moles) of sulphamic acid in 25.0 cm3 of solution.

(1)

(iii) Hence calculate the amount (moles) of sodium hydroxide in the mean titre.

(1)

(iv) Hence calculate the concentration, in mol dm3, of the sodium hydroxide.

(1) Q2

(Total 20 marks)

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*N26025A0812*

3. You are provided with:

A tube containing zinc powder

A solution of copper(II) sulphate of concentration 0.25 mol dm3

(a) Procedure You are advised to read through this procedure before you start.

1. Use a measuring cylinder to transfer 30 cm3 of the copper(II) sulphate solution

into a plastic cup held securely in a beaker.

2. Measure its temperature to the nearest 0.5 C at half minute intervals for the first

three minutes. Record these temperatures in Table 3.

3. At exactly 3.5 minutes add the whole of the sample of zinc powder to the contents

of the plastic cup and stir vigorously and continuously with the thermometer.

4. Measure the temperature from minute 4 to minute 7 at half minute intervals andcomplete Table 3.

Table 3

Time/min 0 0.5 1 1.5 2 2.5 3 3.5

T/C

Time/min 4 4.5 5 5.5 6 6.5 7

T/C

(2)

(b) Observe the contents of the plastic cup and state whether the zinc or the

copper(II) sulphate was in excess. Justify your answer.

.......................................................................................................................................

.......................................................................................................................................

(2)

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(c) Plot a graph of temperature against time.

(3)

(d) Calculations

(i) Use the graph to find the change in temperature, T, for the reaction. Show on

the graph how this was calculated.

(4)

(ii) Use the expression below to calculate the enthalpy change for the reaction.

7.5H =

30 4 18.kJ mol 1

(1)

T e m p e r a t u r e

/

C

0 1 2 3 4 5 6 7

T i m e / m i n

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*N26025A01112*

4. Barium chloride is a soluble salt.

Plan an experiment to determine the percentage, by mass, of barium ions in a sample of

barium chloride containing some potassium chloride.

You are given a solution of sulphuric acid and the usual laboratory apparatus.

Your plan should include the procedure you would use and a brief outline of the calculations

needed.

You are not required to carry out your plan.

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TOTAL FOR PAPER: 50 MARKS

END

Q4

(Total 7 marks)

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