Paper 3

Centre Number

Candidate Number

Candidate Name

UNIVERSITY OF CAMBRIDGE LOCAL EXAMINATIONS SYNDICATE General Certificate of Education Ordinary Level

5070/3

CHEMISTRY PAPER 3 Practical Test MAY/JUNE SESSION 2000

Morning

1 hour 30 minutes

Candidates answer on the question paper. Additional materials: As listed in Instructions to Supervisors Mathematical tables and/or calculator

TIME

1 hour 30 minutes

INSTRUCTIONS TO CANDIDATES Write your name, Centre number and candidate number in the spaces at the top of this page. Answer both questions. Write your answers in the spaces provided on the question paper. You should show the essential steps in any calculation and record all experimental results in the spaces provided on the question paper. If you are using semi-micro methods in Question 2, you should modify the instructions to suit the size of apparatus and the techniques you are using. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. Question 1 carries 45% of the total marks and Question 2 carries 55%. Mathematical tables are available. You may use a calculator. Qualitative Analysis notes for this paper are printed on page 8.

FOR EXAMINER’S USE 1 2 TOTAL

This question paper consists of 7 printed pages and 1 blank pages. SB (DJ) QF06370/3 © UCLES 2000

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For Examiner’s Use

2 1

Hydrated iron(II) sulphate forms crystals of formula FeSO4.x H2O. P is a solution of 27.0 g of FeSO4.x H2O dissolved in 1.00 dm3 of dilute sulphuric acid. Q is 0.0200 mol/dm3 potassium manganate(VII). You are to determine the value of x in the formula FeSO4.x H2O by titrating P with Q. No indicator is necessary since the products of the reaction are almost colourless and one drop of the potassium manganate(VII) solution in excess produces a pale pink colour. (a) Put the potassium manganate(VII) solution Q into the burette. Because the colour of Q is so intense, you may find it easier to read the top of the meniscus. Pipette a 25.0 cm3 (or 20.0 cm3) portion of P into a flask and titrate with Q. At first, the purple colour disappears rapidly. As the titration proceeds, this disappearance is less rapid. At the end-point, one drop of Q produces a pink colour that does not disappear on swirling. Record your results in the table, repeating the titration as many times as you consider necessary to achieve consistent results. Results Burette readings Titration number

1

2

Final reading/cm3 Initial reading/cm3 Volume of Q used/cm3 Best titration results (✔) Summary Tick (✔) the best titration results. Using these results, the average volume of Q required was .…………… cm3. Volume of solution P used .…………… cm3

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[12]

For Examiner’s Use

3 (b) Q is 0.0200 mol/dm3 potassium manganate(VII). Five moles of iron(II) sulphate react with one mole of potassium manganate(VII). Using your results from (a), calculate the concentration, in mol/dm3, of the iron(II) sulphate in P.

The concentration of iron(II) sulphate in P is .......................... mol/dm3.

[2]

(c) P contains 27.0 g of FeSO4.x H2O dissolved in 1.00 dm3 of solution. Using your answer from (b), calculate the relative molecular mass of FeSO4.x H2O.

relative molecular mass of FeSO4.x H2O ..........................

[2]

(d) The relative molecular masses of FeSO4 and H2O are 152 and 18 respectively. Using your answer from (c), calculate the value of x in the formula FeSO4.x H2O.

The value of x is .......................... .

[2]

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4 2

You are provided with three solutions R, S and T, all of which contain sodium salts. Carry out the following experiments and record your observations in the table. Tests on Solution R Test no.

Test

1

To a portion of solution R, add an equal volume of solution Q (from Question 1).

2

(a) To a portion of acidified aqueous potassium manganate(VII), add a few drops of solution R.

Observations

(b) Add an excess of solution R to the mixture from (a).

Divide the mixture from (b) into two parts and use them for Tests 3 and 4 3

To a portion of the mixture from Test 2, add an equal volume of the organic liquid L. Mix well and leave to stand.

4

To a portion of the mixture from Test 2, add an equal volume of solution T and leave to stand.

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For Examiner’s Use

For Examiner’s Use

5 5

To a portion of solution R, add an equal volume of aqueous silver nitrate.

[11] Tests on Solution S Test no. 6

Test

Observations

To a portion of acidified aqueous potassium manganate (VII), add an equal volume of solution S.

Divide this mixture into two parts and use them for Tests 7 and 8. 7

To a portion of the mixture from Test 6, add an equal volume of the organic liquid L. Mix well and leave to stand.

8

To a portion of the mixture from Test 6, add an equal volume of solution T and leave to stand.

9

To a portion of solution S, add an equal volume of aqueous silver nitrate.

[5] 5070/3 J00

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For Examiner’s Use

6 Test on Solution T Test no. 10

Test

Observations

To a portion of aqueous silver nitrate, add a few drops of solution T. Leave to stand for a few minutes, shaking occasionally.

[3] Conclusions The formula of the negative ion present in R is ....................... . In Test 4, solution T is acting as .............................................. . S contains sodium and one other element. Suggest to which group in the Periodic Table this other element belongs. ..............................................................................................................................................[3]

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7 BLANK PAGE

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8 NOTES FOR USE IN QUALITATIVE ANALYSIS Test for anions anion

test

test result

– carbonate (CO23 )

add dilute acid

effervescence, carbon dioxide produced

– chloride (Cl ) [in solution]

acidify with dilute nitric acid, then add aqueous silver nitrate

white ppt.

iodide (I –) [in solution]

acidify with dilute nitric acid, then add aqueous lead(II) nitrate

yellow ppt.

nitrate (NO3) [in solution]

add aqueous sodium hydroxide then aluminium foil; warm carefully

ammonia produced

– sulphate (SO24 ) [in solution]

acidify with dilute nitric acid, then add aqueous barium nitrate

white ppt.

–

Test for aqueous cations cation

effect of aqueous sodium hydroxide

effect of aqueous ammonia

aluminium (Al 3+)

white ppt., soluble in excess giving a colourless solution

white ppt., insoluble in excess

ammonium (NH+4 )

ammonia produced on warming

–

white ppt., insoluble in excess

no ppt. or very slight white ppt.

light blue ppt., insoluble in excess

light blue ppt., soluble in excess giving a dark blue solution

+ iron(II) (Fe2 )

green ppt., insoluble in excess

green ppt., insoluble in excess

iron(III) (Fe3+)

red-brown ppt., insoluble in excess

red-brown ppt., insoluble in excess

zinc (Zn2+)

white ppt., soluble in excess giving a colourless solution

white ppt., soluble in excess giving a colourless solution

2+)

calcium (Ca copper(II)

(Cu2+)

Test for gases gas

test and test result

ammonia (NH3)

turns damp red litmus paper blue

carbon dioxide (CO2)

turns limewater milky

chlorine (Cl 2)

bleaches damp litmus paper

hydrogen (H2)

“pops” with a lighted splint

oxygen (O2)

relights a glowing splint

sulphur dioxide (SO2)

turns aqueous potassium dichromate(VI) from orange to green

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