June 1999 Paper 4

Centre Number

Candidate Number

Candidate Name

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

5070/4

CHEMISTRY PAPER 4 Alternative to Practical Thursday

24 JUNE 1999

Morning

1 hour

Candidates answer on the question paper. Additional materials: Mathematical tables Ruler (cm/mm)

TIME

1 hour

INSTRUCTIONS TO CANDIDATES Write your name, Centre number and candidate number in the spaces at the top of this page. Answer all questions. Write your answers in the spaces provided on the question paper. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. You should use names, not symbols, when describing all reacting chemicals and the products formed. Mathematical tables are available. You may use a calculator.

FOR EXAMINER’S USE

This question paper consists of 15 printed pages and 1 blank page. SB (CW) QF92366/3 © UCLES 1999

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2 1

For Examiner’s Use

What is the volume of liquid, to the nearest cm3, in the measuring cylinder? cm 3 50

40

30

20

10

...................................... cm3

2

[1]

A student was given some 0.100 mol/dm3 hydrochloric acid and did some tests with it to investigate its properties. (a) A few drops of litmus solution were added to 5 cm3 of hydrochloric acid. An excess of aqueous sodium hydroxide was added. What colour change was seen? The colour changed from .......................... to ..........................

[1]

(b) A small piece of magnesium was added to 5 cm3 of hydrochloric acid. A gas was produced. Name the gas. .......................................................................................................................................... Give a test for the gas. .......................................................................................................................................... ......................................................................................................................................[2]

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3

For Examiner’s Use

(c) A few grams of powdered calcium carbonate were added to 5 cm3 of hydrochloric acid. (i)

What did the student observe? ..................................................................................................................................

(ii)

Name the gas evolved. ..................................................................................................................................

(iii)

Give a test for this gas. .................................................................................................................................. .................................................................................................................................. [3]

3

A student used zinc to prepare zinc nitrate. The zinc nitrate was then heated to produce zinc oxide. Some zinc was put in a weighed evaporating dish. The dish was reweighed. Mass of dish + zinc Mass of dish

= =

22.20 g 15.70 g

(a) Calculate the mass of zinc. The mass of zinc = ................ g.

[1]

An acid was slowly added until all the zinc had dissolved. Zinc nitrate solution was produced.

(b) Name the acid. ......................................................................................................................................[1] The solution was evaporated to dryness and the resultant solid was heated in a fume cupboard. The following reaction took place. 2Zn(NO3)2 → 2ZnO + 4NO2 + O2 (c) Why was the heating done in a fume cupboard? .......................................................................................................................................... ......................................................................................................................................[1]

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4

For Examiner’s Use

After cooling, the dish was weighed. It was then heated again, cooled and reweighed. (d) Why was the dish heated again? ......................................................................................................................................[1] Final mass of dish + zinc oxide = 23.40 g (e) Calculate the mass of zinc oxide. .......................................................................................................................... g (f)

[1]

Using your answers to (a) and (e), calculate the percentage yield of zinc oxide from the initial mass of zinc. Ar : Zn, 65; O, 16.

......................................................................................................................................[2] In Questions 4 – 7 inclusive place a tick (✔) in the box against the best answer. 4

A gas, when passed through aqueous potassium dichromate(VI), changed the colour of the solution from orange to green. Which gas was used? (a) chlorine (b) ethane (c) oxygen (d) sulphur dioxide [1]

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5 5

A student was given a sample of damp soil which was known to be acidic. Which of the following substances cannot be used to neutralise the soil?

For Examiner’s Use

(a) ammonia (b) lime (c) salt (d) slaked lime [1]

6

Several strips of a metal X were placed in test-tubes containing aqueous solutions as shown in the diagrams. metal X

metal X

metal X

metal X

CaCl 2(aq)

CuCl 2(aq)

NaCl (aq)

ZnCl 2(aq)

A deposit was seen on X in two tubes only. What was metal X ? (a) iron (b) magnesium (c) potassium (d) silver [1]

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6 7

For Examiner’s Use

Four experiments were set up to find out how nails could be prevented from rusting.

oxygen

air

air

oxygen

layer of oil

painted nails in tap water (a)

unpainted nails in a solid drying agent (b)

unpainted nails in distilled water (c)

unpainted nails in boiled tap water (d)

In which tube did the nails rust? (a) (b) (c) (d) [1]

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7 8

For Examiner’s Use

P is a mixture of iron(II) sulphate and iron(III) sulphate. A student determined the percentage of iron(II) sulphate in the mixture by using 0.0200 mol/dm3 potassium manganate(VII), solution R. A sample of P was added to a previously weighed container, which was then reweighed. Mass of container + P Mass of container

= =

19.16 g 12.98 g

(a) Calculate the mass of P used in the experiment. ...........................................................................................................................g

[1]

The sample of P was placed in a flask, dissolved in 100 cm3 of dilute sulphuric acid and the solution was made up to 250 cm3 with distilled water. This was solution S. A 25.0 cm3 sample of S was measured into a conical flask. (b) What should be used to measure this volume? ......................................................................................................................................[1] Potassium manganate(VII), which is purple, oxidises iron(II) ions in the mixture. (c) Suggest why potassium manganate(VII) does not react with iron(III) ions. .......................................................................................................................................... ......................................................................................................................................[1] Solution R was run from the burette into a flask containing S. (d) How would the student know when the end-point was reached? .......................................................................................................................................... ......................................................................................................................................[1]

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8 (e) Three such titrations were done. Parts of the burette before and after each titration are shown below. 0

24

2

25

17

42

1

25

3

26

18

43

2

26

4

27

19

44

Using the diagrams, complete the following table. titration number

first

second

third

final burette reading / cm3 initial burette reading / cm3 volume of R used / cm3 best titration results (✓)

Summary: Tick (✔) the best titration results. Using these results, the average volume of R required was ......................... cm3

[4]

R is 0.0200 mol/dm3 potassium manganate(VII). (f)

Calculate how many moles of potassium manganate(VII) were present in the average volume of R calculated in (e).

................................. moles of KMnO4

[1]

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For Examiner’s Use

9

For Examiner’s Use

(g) One mole of KMnO4 reacts with five moles of iron(II) sulphate, FeSO4. Calculate how many moles of FeSO4 were present in 25.0 cm3 of S.

................................. moles of FeSO4

[1]

(h) Calculate how many moles of FeSO4 were present in 250 cm3 of S.

................................. moles of FeSO4 (i)

[1]

Using your answer to (h), calculate the mass of FeSO4 present in the solution of S. (Mr: FeSO4, 152)

................................. g of FeSO4 (j)

[1]

Using your answers to (a) and (i), calculate the percentage of FeSO4 in the sample of P.

[1]

................................. % of FeSO4

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10 9

The following table shows the tests a student did on substance G and the conclusions made from the observations. Complete the table by describing these observations and describe the test and observations which led to the conclusion from test 4. test 1

G was dissolved in water and the solution divided into three parts for tests 2, 3 and 4.

2

(a) To the first part, aqueous sodium hydroxide was added until a change was seen.

observations

G is not a compound of a transition metal.

G may contain Zn2+ ions.

(b) An excess of aqueous sodium hydroxide was added to the mixture from (a). 3

conclusions

(a) To the second part, aqueous ammonia was added until a change was seen.

The presence of Zn2+ ions is confirmed.

(b) An excess of aqueous ammonia was added to the mixture from (a).

G contains I– ions.

4

Conclusion: The formula for substance G is ...........................................................

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[9]

For Examiner’s Use

11

For Examiner’s Use

10 A student plated a metal ring with silver using the apparatus shown below.

A

variable resistor +

–

aqueous silver nitrate carbon (graphite) anode

metal ring

The ring was weighed and placed in the solution. This was the cathode. The circuit was completed and a current of 1 A was allowed to flow. (a) What was the purpose of the variable resistor? ......................................................................................................................................[1]

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12 The ring was removed every ten minutes, carefully washed, dried and weighed. This was experiment I. The experiment was repeated using a current of 1.5 A. This was experiment II. The results from both experiments are shown in the table. (b) Complete the table by calculating the total increase in mass after each ten minutes in both experiments. experiment I

experiment II

current 1 A

current 1.5 A

time/min

mass of ring/g

total increase in mass/g

0

8.80

0.00

8.80

0.00

10

9.10

0.30

9.25

0.45

20

9.40

0.60

9.70

30

9.70

10.15

40

10.00

10.60

50

10.30

10.60

60

10.60

10.60

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mass of ring/g

total increase in mass/g

[2]

For Examiner’s Use

13 (c) Plot the two sets of results on the grid below. Join each set of results using straight lines. Label the lines I and II corresponding to the two experiments.

For Examiner’s Use

2.0

1.8

1.6

1.4

1.2 total increase in mass /g

1.0

0.8

0.6

0.4

0.2

0 0

10

20

30

40

50

60

time/min [4]

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14

For Examiner’s Use

(d) What was the time taken to deposit 1.00 g of silver in each experiment? I

................................................... g

II

................................................... g

[2]

(e) Calculate how much more silver was deposited after 15 minutes in experiment II than in experiment I. mass of silver deposited in 15 minutes in II ................................................... g mass of silver deposited in 15 minutes in I ................................................... g difference in mass = .......................... g (f)

[2]

Predict the mass of silver deposited in experiment I if the experiment had continued for 70 minutes. Explain your answer. ....................................................................................................................................... g Explanation ...................................................................................................................... ......................................................................................................................................[2]

(g) Suggest how the rate of deposition of a metal during electrolysis is influenced by the value of the current. ......................................................................................................................................[1]

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15 11 A student did the following experiments with copper powder. (a) He heated the copper powder in air and a black solid was formed. Name the compound formed. ......................................................................................................................................[1] (b) A small volume of dilute sulphuric acid was added to the substance formed in (a). The solid reacted with the acid to form a solution. (i)

What was the colour of the solution? ..................................................................................................................................

(ii)

Name the solution. .................................................................................................................................. [2]

(c) Some powdered zinc was added to the solution formed in (b) and left for a while. Describe what was seen. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3]

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For Examiner’s Use

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