June 1999 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 Thursday

24 JUNE 1999

Morning

1 hour 30 minutes

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

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 35% of the total marks and Question 2 carries 65%. Mathematical tables are available. Qualitative Analysis notes for this paper are printed on page 8.

FOR EXAMINER’S USE 1 2 TOTAL

This question paper consists of 5 printed pages and 3 blank pages. SB (SC) QF92365/2 © UCLES 1999

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2 1

For Examiner’s Use

Solution Q is aqueous sodium hydroxide of unknown concentration. Solution P is 0.100 mol/dm3 hydrochloric acid. (a) Put P into the burette. Pipette a 25.0 cm3 (or 20.0 cm3) portion of Q into a flask and titrate with P, using the indicator provided. Record your results in the table, repeating the whole procedure 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 P used/cm3 Best Titration results (✔)

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

[12]

(b) P is 0.100 mol/dm3 hydrochloric acid Using your answer to (a) calculate the concentration, in mol/dm3, of sodium hydroxide in Q.

Concentration of sodium hydroxide in Q is ……………. mol/dm3

5070/3 S99

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3 BLANK PAGE

5070/3 S99

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4 2

Test No. 1

You are provided with three solutions, R, S and T, which have been prepared by dissolving three different metal oxides in dilute nitric acid. Carry out the following experiments on the solutions and record your observations in the table.

Test

Observations with Solution R

(a) To a portion of the test solution, add aqueous sodium hydroxide until a change is seen.

(b) Add excess aqueous sodium hydroxide to the mixture from (a).

2

For Examiner’s Use

(a) To a portion of the test solution, add aqueous ammonia until a change is seen.

(b) Add excess aqueous ammonia to the mixture from (a).

3

To a portion of the test solution, add an equal volume of aqueous potassium iodide and leave to stand for a few minutes.

4

To a portion of the test solution, add an equal volume of dilute sulphuric acid.

5070/3 S99

5 Observations with Solution S

For Examiner’s Use

Observations with Solution T

Test No. 1

2

3

4

[23] Conclusions Give the name of the metal present in R ........................................................................................ Name the section of the Periodic Table in which the metal in S is found ........................................ Is the metal oxide used to prepare T acidic, amphoteric or basic? (Underline the correct answer) 5070/3 S99

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5070/3 S99 5070/3 S99

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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 (NO–3) [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) green

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