Chemstry June 2001 - Paper 4

Centre Number

Candidate Number

Candidate Name

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

CHEMISTRY

5070/4

PAPER 4 Alternative to Practical MAY/JUNE SESSION 2001

1 hour

Candidates answer on the question paper. No additional materials required.

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.

FOR EXAMINER’S USE

This question paper consists of 16 printed pages. SB (CW/KN) QF10460/4 © UCLES 2001

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2 1

(a) Which of the following pieces of apparatus is best used for accurately measuring 25.0 cm3 of a liquid? A

B

C

50 40 30 20

10

20

30

40

50

25 cm3

10

......................................................................................................................................[1] (b) Name the piece of apparatus that you have chosen. ......................................................................................................................................[1]

2

A student placed 100 cm3 of 0.100 mol / dm3 ammonia in a beaker. A piece of litmus paper was dipped into the solution. (a) (i)

What colour was the litmus paper in the solution? ...................................................................................................................................

(ii)

How could the pH of the solution be measured? ................................................................................................................................... [2]

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3 The ammonia was neutralised by the addition of dilute nitric acid and a salt was formed. (b) (i)

For Examiner’s Use

Name the salt. ...................................................................................................................................

(ii)

Give the chemical formula of the salt. ...................................................................................................................................

(iii)

The student produced some crystals of the salt from the solution. How was this done? ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... [4]

(c) The salt is used industrially as a fertiliser. Which element in the fertiliser is necessary for the growth of plants? ......................................................................................................................................[1]

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4 3

A student electrolyses aqueous copper(II) sulphate, using carbon electrodes. The apparatus is shown below.

+

–

A

B

carbon electrodes

aqueous copper(II) sulphate

After a few minutes, a pink solid is deposited on one electrode and a gas is evolved at the other electrode. (a) (i)

At which electrode, A or B, is the pink solid deposited? ...................................................................................................................................

(ii)

Name this pink solid. ...................................................................................................................................

(iii)

Name the gas evolved at the other electrode. ...................................................................................................................................

(iv)

Give a test for this gas. test ............................................................................................................................ result ......................................................................................................................... ................................................................................................................................... [4]

How does the colour of the electrolyte change during the electrolysis? (b) (i) (ii)

from ........................................................... to ........................................................... Why does the change take place? ................................................................................................................................... [3]

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5 Eventually, no more of the pink solid is formed. Instead, a gas is given off from the electrode. (c) (i)

For Examiner’s Use

Name this gas. ...................................................................................................................................

(ii)

Give a test for this gas. test ............................................................................................................................ result ......................................................................................................................... ...............................................................................................................................[2]

In questions 4 to 7, place a tick against the best answer. 4

A student converted starch into ethanol by a process involving two stages. An acid was used in stage A and yeast in stage B. A B STARCH → SUGAR → ETHANOL What are the stages A and B? A

B

(a) distillation → esterification (b) distillation → fermentation (c) hydrolysis → esterification (d) hydrolysis → fermentation [1]

5

In which of the following reactions is hydrogen not produced? (a) magnesium and hydrochloric acid (b) sodium and water (c) calcium carbonate and hydrochloric acid (d) iron and steam [1]

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6 6

Substance Y was added to aqueous bromine. The colour of the bromine changed from brown to colourless. What could Y have been? (a) H

(b) H

(c) H

H

H

H

C

C

C

H

H

H

H

H

C

C

H

H

H

H

H

C

C

C

H H

C H

H

H

H (d)

O

H

O C O

H [1]

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7 7

A student added 10.0 cm3 of 0.100 mol / dm3 hydrochloric acid to an excess of zinc pieces. The volume of hydrogen produced was recorded at time intervals until no more gas was produced. This was experiment P. The experiment was repeated using 10.0 cm3 of 0.100 mol / dm3 sulphuric acid and an excess of zinc powder. This was experiment Q. Which of the following graphs was obtained? (a)

(b)

volume of H2 –––––– cm3

volume of H2 –––––– cm3

Q P

Q

P 0

0 0

0

time/s

(c)

time/s

(d)

Q volume of H2 –––––– cm3

Q

volume of H2 –––––– cm3

P

0

P

0 0

0

time/s

time/s

[1]

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8 8

M CO3 is a metal carbonate. A student did an experiment to find • the relative molecular mass of M CO3 • the relative atomic mass of M. A sample of M CO3 was added to a previously weighed container which was then re-weighed. Mass of container + M CO3 Mass of container

= =

9.01 g 7.98 g

(a) Calculate the mass of M CO3 used in the experiment. ......................................................................................................................................[1] The sample was placed in a volumetric flask to which 50.0 cm3 of 1.00 mol / dm3 hydrochloric acid (an excess) were added. A gas was evolved. (b) (i)

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

(ii)

Give a test for the gas. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... [2]

When no more gas was evolved, the solution was made up to 250 cm3 with distilled water. This was solution R. A 25.0 cm3 sample of R was transferred to a titration flask and a few drops of methyl orange indicator were added. Then, 0.100 mol / dm3 sodium hydroxide was run into R from a burette until an end point was reached. (c) What was the colour change of the methyl orange? The colour changed from ............................................ to .............................................[2]

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9 (d) Three such titrations were done. Parts of the burette with liquid levels before and after each titration are shown below. first titration

second titration

For Examiner’s Use

third titration

0

24

2

28

21

46

1

25

3

29

22

47

2

26

4

30

23

48

3

27

5

31

24

49

Use the above diagrams to complete the following results table. titration number

first

second

third

Final burette reading / cm3 Initial burette reading / cm3 Volume of 0.100 mol / dm3 sodium hydroxide required / cm3 Best titration results (✔)

Summary Tick the best titration results. Using these results, the average volume of 0.100 mol / dm3 sodium hydroxide was ..................... cm3.

[4]

(e) Calculate how many moles of sodium hydroxide are in the average volume of 0.100 mol / dm3 sodium hydroxide in (d).

......................................................................................................................................[1]

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10 .

(f)

Using the equation NaOH + HCl → NaCl + H2O calculate how many moles of hydrochloric acid are in 25.0 cm3 of R.

......................................................................................................................................[1] (g) Calculate how many moles of hydrochloric acid are in 250 cm3 solution of R.

......................................................................................................................................[1] (h) Calculate how many moles of hydrochloric acid were originally taken in 50.0 cm3 of 1.00 mol / dm3 hydrochloric acid.

......................................................................................................................................[1] (j)

By subtracting your answer (g) from (h), calculate how many moles of hydrochloric acid reacted with the M CO3.

......................................................................................................................................[1] (k) One mole of M CO3 reacts with two moles of hydrochloric acid. Calculate how many moles of M CO3 were present in the original sample.

......................................................................................................................................[1]

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11 (l)

(Ar: C,12; O,16) Using your answers to (k) and (a), calculate (i)

the mass of one mole M CO3,

(ii)

the relative atomic mass of M.

...............................................................................................................................[3]

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12 9

The following table shows the tests a student did on V, an anhydrous salt, and the conclusions made from the observations. Complete the table by describing these observations and suggest the test and observations which led to the conclusion from test 4. test 1

V 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.

observation

V is a compound of a transition metal.

V may contain Fe3+ ions.

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

conclusion

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

The presence Fe3+ ions confirmed.

of is

(b) An excess of aqueous ammonia was added to the mixture from (a). 4

V contains Cl – ions.

Conclusions The formula for V is .............................................................................................................[9]

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13 10 When sulphuric acid was added to aqueous sodium hydroxide, a rise in temperature was observed.

For Examiner’s Use

A student added dilute sulphuric acid from a burette to 1.00 mol / dm3 sodium hydroxide, using the apparatus shown below. The temperature both of the sodium hydroxide and of the sulphuric acid was 25 °C.

burette thermometer dilute sulphuric acid stirrer

insulated beaker 1.00 mol/dm3 sodium hydroxide 20.0 cm3 sample of 1.00 mol / dm3 sodium hydroxide was placed in the beaker. To the 20.0 cm3 of sodium hydroxide, 5.0 cm3 of sulphuric acid were added from the burette and the temperature was recorded. Further 5.0 cm3 portions of acid were added and each time the temperature was recorded.

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14 The diagrams below show the parts of the thermometer stem giving the temperatures after the addition of 5.0 cm3, 15.0 cm3, 25.0 cm3 and 35.0 cm3 of sulphuric acid.

30

35

35

35

25

30

30

30

20

25

25

25

Addition of 5.0 cm3 of sulphuric acid

Addition of 15.0 cm3 of sulphuric acid

Addition of 25.0 cm3 of sulphuric acid

Addition of 35.0 cm3 of sulphuric acid

(a) Use the diagram to complete the following table. volume of sulphuric acid added / cm3

temperature / °C

0

25

5.0 15.0 25.0 35.0 45.0

28

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[2]

For Examiner’s Use

15 (b) Plot these results on the grid below. Join up the points with two straight lines which intersect and use the resulting graph to answer the questions below.

For Examiner’s Use

35

30

temperature /°C

25

20

0

5

10

15

20

25

30

35

40

45

volume of sulphuric acid added / cm3 [3] (c) (i)

Use your graph to deduce the highest temperature reached. ...................................................................................................................................

(ii)

What volume of sulphuric acid produced this highest temperature? ...............................................................................................................................[2]

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16 (d) The volume of acid in (c) (ii) neutralises 20.0 cm3 of 1.00 mol / dm3 sodium hydroxide. 2 NaOH + H2SO4 → Na2SO4 + 2H2O Deduce the concentration, in mol / dm3, of the sulphuric acid.

......................................................................................................................................[1] The experiment was repeated using 20.0 cm3 of 0.50 mol / dm3 sodium hydroxide and sulphuric acid of concentration of 0.50 mol / dm3. The initial temperature of each solution was 25 °C, the same as in the first experiment. (e) (i)

Suggest the volume of sulphuric acid required to produce the highest temperature. ...................................................................................................................................

(ii)

Suggest whether the temperature would be higher, lower or the same as in the first experiment. Explain your answer. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... [3]

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