2012 June ISA CHEM6TP Question Paper

WMP/Jun12/CHM6T/P12/test CHM6T/P12/test

General Certificate of EducationAdvanced Level ExaminationJune 2012

For this paper you must have:l the Periodic Table/Data Sheet provided at the end of this paperl the Task Sheet and your Candidate Results Sheetl a ruler with millimetre measurementsl a calculator.

Time allowedl 1 hour

Instructions:l Use black ink or black ball-point pen.l Fill in the boxes at the top of this page.l Answer all questions.l You must answer the questions in the spaces provided. Do not

write outside the box around each page or on blank pages.l Do all rough work in this book. Cross through any work you do not

want to be marked.

Informationl The marks for questions are shown in brackets.l The maximum mark for this paper is 30.l You will be marked on your ability to:

organise information clearly use scientific terminology accurately.

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Yes No

Teacher Declaration:I confirm that the candidates work was conducted under the conditions laid out by the specification. I have authenticated thecandidates work and am satisfied that to the best of my knowledge the work produced is solely that of the candidate.

Signature of teacher ................................................................................................................... Date ..........................................

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Notice to Candidate. The work you submit for assessment must be your own. If you copy from someone else or allow another candidate to copy from you, or if you cheat in any other way, you may be disqualified.

Candidate Declaration. I have read and understood the Notice to Candidate and can confirm thatI have produced the attached work without assistance other than that which is acceptable under the schemeof assessment.

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For Teachers Use

Section Mark

PSA

Task

Section A

Section B

TOTALISA MARK

(max 50)

Chemistry CHM6T/P12/testUnit 6T A2 Investigative Skills Assignment

Written Test

For submission by 15 May 2012

WMP/Jun12/CHM6T/P12/test

Do not writeoutside the

box

1 The tests used in the Task were repeated using a solution of salicylic acid. Theobservations are shown below.

Use the observations in the table and your results from the Task to deduce which oneof the solutions, A, B, C or D, contains salicylic acid.

............................................................................................................................................(1 mark)

2 Use your results from the Task to suggest which one of the solutions, A, B, C or D,contains sulfuric acid. Give a reason for your choice.

Solution ..............................................................................................................................

Reason ...............................................................................................................................

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

............................................................................................................................................(2 marks)

3 Use the observations in the table and your results from the Task to select the pH rangein which bromothymol blue indicator changes colour.

l 25l 58l 811

Give a reason for your choice.

pH range ............................................................................................................................

Reason ..............................................................................................................................

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

............................................................................................................................................(2 marks)

Section A

These questions are about the task, an investigation of salicylic acid.

You should use your Task Sheet and your Candidate Results Sheet to answer them.

Answer all questions in the spaces provided.

2

Bromothymolblue

Copper(II)carbonate

Bariumchloride solution

salicylic acidyellow

solutioneffervescenceblue solution

no visible change


Turn over


box

4 A test using sodium chloride and silver nitrate solutions can be used to identify thesolution containing ammonia.

Give brief details of this test and include the observations that would be made.

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

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

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

............................................................................................................................................(2 marks)

5 When 1.00 mol dm3 solutions of salicylic acid and sodium hydroxide are mixed abuffer solution can be formed. Salicylic acid is a monoprotic acid that can berepresented by the formula HA.

5 (a) Select a mixture from the table below that would produce a buffer solution. Give areason for your choice.

Mixture ...............................................................................................................................

Reason ...............................................................................................................................

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

............................................................................................................................................(2 marks)

5 (b) Another mixture, formed by adding 50 cm3 of 1.00 mol dm3 salicylic acid solution to 25 cm3 of 1.00 mol dm3 sodium hydroxide solution, can be used to determine the pKaof salicylic acid. State one measurement that must be made for this mixture andexplain how this measurement can be used to determine the pKa of salicylic acid.

Measurement .....................................................................................................................

Explanation ........................................................................................................................

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

............................................................................................................................................(3 marks)

3

12

MixtureVolume of 1.00 mol dm3

salicylic acid solution / cm3Volume of 1.00 mol dm3

sodium hydroxide solution / cm3

X 25 75

Y 50 50

Z 75 25



box

4

6 A student was given a task to determine the percentage purity of a sample of salicylicacid. The method used by the student to prepare a solution of salicylic acid isdescribed below.

l 0.500 g of an impure sample of salicylic acid was placed in a weighing bottle.l The contents were tipped into a beaker and 100 cm3 of distilled water were

added.l Salicylic acid does not dissolve well in cold water so the beaker and its contents

were heated gently until all the solid had dissolved.l The solution was poured into a 250 cm3 graduated flask and made up to the

mark with distilled water.

6 (a) Give two additional instructions that would improve this method for making up thesalicylic acid solution.

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

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

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

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

............................................................................................................................................(2 marks)

6 (b) The pH of this solution was measured and a value of 2.50 was obtained.Calculate the concentration of salicylic acid in this solution.Assume that salicylic acid is the only acid in this solution. The Ka for salicylic acid is1.07 103 mol dm3. You may represent salicylic acid as HA.Show your working.

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

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

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

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

............................................................................................................................................(3 marks)

Section B

Answer all questions in the spaces provided.



box

5

Turn over

6 (c) Use your answer to part 6 (b) to calculate the mass of salicylic acid (Mr = 138.0)present in the original sample.(If you were unable to complete the calculation in part 6 (b), assume that theconcentration of salicylic acid is 8.50 103 mol dm3. This is not the correct answer.)

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

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

............................................................................................................................................(2 marks)

6 (d) Use your answer to part 6 (c) to calculate the percentage purity of the salicylic acidused to make the solution.(If you were unable to complete the calculation in part 6 (c), assume that the mass ofsalicylic acid is 0.347 g. This is not the correct answer.)

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

............................................................................................................................................(1 mark)

7 Salicylic acid can be used to make aspirin. Before using a sample of salicylic acid tomake aspirin, a student purified the acid by recrystallisation. The method forrecrystallisation is outlined below.

Step 1: The sample is dissolved in a minimum volume of hot water.Step 2: The solution is filtered hot.Step 3: The filtrate is cooled in ice to form crystals.Step 4: The crystals are collected by filtration, washed with cold water and left to dry.

Explain the purpose of each underlined point.

Minimum volume ...............................................................................................................

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

Hot water ...........................................................................................................................

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

Filtered hot .........................................................................................................................

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

Cooled in ice ......................................................................................................................

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

Washed with cold water ....................................................................................................

............................................................................................................................................(5 marks)



box

8 Aspirin can be made by reacting salicylic acid with ethanoic anhydride as outlinedbelow.

8 (a) In an experiment, after purification by recrystallisation, 1.76 g of aspirin (Mr = 180.0)were produced from 2.00 g of salicylic acid.Calculate the percentage yield for this experiment.

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

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

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

............................................................................................................................................(2 marks)

8 (b) Suggest one practical reason why the yield of purified aspirin is less than 100%.

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

............................................................................................................................................(1 mark)

6

CO

OCH3

CO

CH3

OC

OHCH3

CO

OH

OH

+ +

CO

O CH3

OH

C

O



box

9 Salicylic acid, C6H4(OH)COOH, reacts with magnesium to produce magnesiumsalicylate and hydrogen.

9 (a) Complete the equation for this reaction.

C6H4(OH)COOH

(1 mark)

9 (b) In an alternative method for determining percentage purity, a student reacted a solutionof salicylic acid with an excess of magnesium and collected the hydrogen gas that wasreleased.

Complete the diagram below to show an apparatus that could be used to collect andmeasure the volume of hydrogen gas produced.

(1 mark)

END OF QUESTIONS

7

Salicylic acid solutionand magnesium

18

Turn over


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Copyright 2011 AQA and its licensors. All rights reserved.

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2012 June ISA CHEM6TP Question Paper