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 2000 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 13 printed pages and 3 blank pages. SB (SLC/DJ) QF06371/4 UCLES 2000 [Turn over

1 (a) Name the apparatus shown below. 2...[1] (b) (i) What safety item should be used with this apparatus? (ii) Why is this safety item used?...[2] 2 A student did two experiments as shown below. air glass disc cold water bromine vapour crystal of copper(ii) sulphate bromine liquid diagram 1 diagram 2

(a) 3 A student was given a crystal of copper(ii) sulphate. He placed the crystal in a beaker of cold water as shown in diagram 1. (i) What is the colour of copper(ii) sulphate crystals? What changes were seen in the appearance of the contents of the beaker. (ii) after a few minutes, (iii) after several hours? [3] (b) The student set up the apparatus as shown in diagram 2. Then he carefully removed the glass disc allowing the contents of the gas jars to mix. What change was seen after a few minutes?......[1] (c) (i) Name the process that was illustrated by both of the experiments. (ii) Explain why the changes observed in (a) took place. (iii) Explain why the change observed in (b) was faster than the change in (a). [3] [Turn over

3 4 + + A B C D molten sodium chloride aqueous sodium chloride heat The diagram shows two electrolytic cells. Each of the electrodes is labelled with a letter. these letters to answer the questions below. (a) At which electrode was a metal produced?...[1] (b) (i) At which two electrodes was the same gas evolved? electrodes... and.... (ii) Name this gas. (iii) Give a test for this gas. [3] (c) (i) Name the other gas evolved in these experiments. (ii) Give a test for this gas. [2]

5 questions 4 to 8 inclusive, place a tick in the box against the best answer. 4 Ethanol may be made by growing yeast in sugar solution. The process is called (a) (b) (c) (d) combustion, cracking, esterification, fermentation. [1] 5 Aqueous barium chloride reacts with aqueous sodium sulphate as shown by the equation BaCl 2 + Na 2 SO 4 BaSO 4 + 2NaCl When 0.20 moles of barium chloride was added to 0.40 moles sodium sulphate the number of moles of barium sulphate produced was (a) 0.20, (b) 0.40, (c) 0.60, (d) 0.80. [1] [Turn over

6 A student added 5 g of zinc to 50 cm 3 of 1.00 mol/dm 3 hydrochloric acid at 20 C. Hydrogen was produced. The experiment was repeated at 30 C and 40 C. In each case the total volume of hydrogen produced was plotted against time. 6 Which one of the graphs represents the volumes of hydrogen given off in the three experiments? 40 C Volume of hydrogen/ cm 3 30 C 20 C Volume of hydrogen/ cm 3 40 C 30 C 20 C 0 0 time/s 0 0 A time/s B Volume of hydrogen/ cm 3 20 C 30 C 40 C Volume of hydrogen/ cm 3 20 C 30 C 40 C 0 0 time/s 0 0 C time/s D (a) (b) (c) (d) A B C D [1]

7 Metal A displaced metal B from a solution of its ions. Metal B displaced metal C from a solution of its ions. 7 What could A, B and C have been? A B C (a) (b) (c) (d) calcium silver zinc calcium zinc silver silver calcium zinc zinc silver calcium [1] 8 A student made a polyamide using the apparatus shown below. The polyamide was formed at the junction of the two liquids. polymer aqueous solution non-aqueous solution The polyamide was (a) (b) (c) (d) nylon, polythene, starch, Terylene. [1] [Turn over

9 Hydrogen peroxide decomposes slowly at room temperature to form water and oxygen. 8 2H 2 O 2 (aq) 2H 2 O(l) + O 2 (g) A student investigated how the rate of decomposition changes by using two catalysts; copper and manganese(iv) oxide. The volume of oxygen produced was measured at intervals. 10 20 30 40 50 gas syringe catalyst hydrogen peroxide (a) Experiment 1, using copper powder (Cu). The diagrams below show the volume of oxygen collected in the syringe after the times stated. Further volumes are shown in the table. 10 20 30 40 50 60 1 min 10 20 30 40 50 60 2 min 10 20 30 40 50 60 3 min 10 20 30 40 50 60 4 min Complete Table 1 for copper by reading the syringes in the diagrams. (b) Experiment 2, using manganese(iv) oxide, MnO 2. The experiment was repeated using manganese(iv) oxide as the catalyst in place of copper. The results are shown in Table 1. Table 1 total volume of oxygen/cm 3 collected after catalyst 1 min 2 min 3 min 4 min 5 min 6 min copper 50 50 manganese(iv) oxide 9 17 24 28 32 35 [2]

9 Plot both sets of results from Experiments 1 and 2 on the grid below and draw a smooth curve through each set of points. Label the curves Cu and MnO 2. 60 50 40 total volume of oxygen collected / cm 3 30 20 10 0 0 1 2 3 4 5 6 time / min [3] (c) Suggest why the last two readings in Experiment 1 were the same.......[1] (d) your graph to estimate the time taken, in each experiment, to double the total volume of oxygen produced from 15 cm 3 to 30 cm 3. Cu MnO 2 time taken to produce 30 cm 3 /min time taken to produce 15 cm 3 /min time taken to double the volume/min [4] [Turn over

(e) (f) (g) 10 Which was the better catalyst, copper or manganese(iv) oxide? Explain your answer..........[2] Suggest a further experiment which could be done to confirm that the two substances are acting as catalysts.......[2] Suggest another way of increasing the rate of decomposition of hydrogen peroxide without using a catalyst....[1]

10 Substance V contains three ions. The following table shows the tests a student did on substance V 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. 11 test observation conclusion 1 V was dissolved in water and the solution divided into three parts for tests 2, 3 and 4. V is a compound of a transition metal. 2 (a) To the first part, aqueous sodium hydroxide was added until a change was seen. (b) (c) The mixture from (a) was warmed. An excess of aqueous sodium hydroxide was added to the mixture from (a). V contains NH 4 + ions. V may contain Fe 2+ ions. 3 (a) To the second part, aqueous ammonia was added until a change was seen. (b) An excess of aqueous ammonia was added to the mixture from (a). The presence of Fe 2+ ions is confirmed. 4 V contains SO 4 2 ions. Conclusion: Ions present in V are...[11] [Turn over

11 A student was given a sample of impure barium hydroxide, Ba(OH) 2. She found the percentage purity by titrating an aqueous solution with 0.098 mol/dm 3 hydrochloric acid. 12 A sample of barium hydroxide was placed in a weighed container which was reweighed. mass of container + barium hydroxide mass of container = 12.16 g = 9.93 g (a) Calculate the mass of the sample of barium hydroxide....[1] This sample of barium hydroxide was transferred to a graduated flask and made up to 250 cm 3 with distilled water. This was solution G. A pipette was used to transfer 25.0 cm 3 of G into a flask. A few drops of methyl orange indicator were added. 0.098 mol/dm 3 hydrochloric acid was added from a burette until an end point was reached. (b) What was the colour change of methyl orange? The colour changed from... to...[2] Three titrations were done. Parts of the burette with the liquid levels before and after each titration are shown below. First Titration Second Titration Third Titration 18 0 24 6 30 42 19 1 25 7 31 43 20 2 26 8 32 44 (c) the diagram to complete the results table. titration first second third final reading/cm 3 first reading/cm 3 volume of hydrochloric acid/cm 3 best titration results ( )

Summary Tick ( ) the best titration results. 13 Using these results, the average volume of hydrochloric acid required was...cm 3. [4] (d) Calculate the number of moles of hydrochloric acid in the average volume of 0.098 mol/dm 3 hydrochloric acid....moles [1] (e) Ba(OH) 2 + 2HCl BaCl 2 + 2H 2 O Using the equation above and your answer to (d), calculate the number of moles of barium hydroxide in 25.0 cm 3 of G....[1] (f) Calculate the number of moles of barium hydroxide in the original 250 cm 3 of G....[1] (g) Calculate the mass of one mole barium hydroxide, Ba(OH) 2 (A r : Ba,137; O,16; H,1)....[1] (h) Using your answers to (f) and (g), calculate the mass of barium hydroxide in the 250 cm 3 solution G....[1] (i) Using your answers to (a) and (h) calculate the percentage purity of the barium hydroxide....[1]

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