Chemistry 0620/63 May/June 2019: question paper and mark scheme

Question

A student investigated the colours present in three hair dyes, P, Q and R, using chromatography. P, Q and R are insoluble in water. The student suggested setting up the apparatus for the experiment as shown. clips glass cover rod chromatography paper beaker solvent (a) Why is a lid necessary on top of the beaker? . …… [1] (b) (i) Identify one mistake in the student’s diagram. . …… [1] (ii) Suggest why this mistake would stop the experiment working. . …… . …… [1] (c) Name a suitable solvent that could be used in this experiment. . …… [1] (d) A separate chromatography experiment was done using the hair dyes P, Q and R. The chromatogram obtained is shown. P Q R State three conclusions about the hair dyes P, Q and R which can be deduced from the chromatogram. 1 . …… 2 . …… 3 . …… [3] [Total: 7]

Question

A student investigated the temperature changes when two different metals, zinc and magnesium, reacted with aqueous copper(II) sulfate. Three experiments were done. Experiment 1 ●● A measuring cylinder was used to pour 25 cm3 aqueous copper(II) sulfate into a polystyrene cup. ●● The initial temperature of the solution was measured and the timer was started. ●● The temperature of the solution was measured at 30 seconds and at 60 seconds. ●● At 60 seconds, 5 g of zinc powder was added to the aqueous copper(II) sulfate. The mixture was stirred with a thermometer. ●● The temperature of the mixture was measured every 30 seconds for 210 seconds. The mixture was stirred continuously. (a) Use the thermometer diagrams to record the temperatures in the table. time / s 0 30 60 90 120 150 180 210 30 30 30 50 50 50 50 50 thermometer 25 25 25 45 45 45 45 45 diagram 20 20 20 40 40 40 40 40 temperature of mixture / °C [2] Experiment 2 ●● Experiment 1 was repeated using 5 g of magnesium powder instead of zinc powder. (b) Use the thermometer diagrams to record the temperatures in the table. time / s 0 30 60 90 120 150 180 210 30 30 30 60 80 80 80 80 thermometer 25 25 25 55 75 75 75 75 diagram 20 20 20 50 70 70 70 70 temperature of mixture / °C [1] Experiment 3 ●● Experiment 1 was repeated using 5 g of zinc granules instead of zinc powder. (c) Use the thermometer diagrams to record the temperatures in the table. time / s 0 30 60 90 120 150 180 210 30 30 30 30 30 30 30 30 thermometer 25 25 25 25 25 25 25 25 diagram 20 20 20 20 20 20 20 20 temperature of mixture / °C [1] (d) Plot the results for Experiments 1–3 on the grid and draw three smooth line graphs. Clearly label your lines. 80 70 60 50 temperature of mixture / °C 40 30 20 10 0 0 30 60 90 120 150 180 210 time / s [3] (e) From your graph, deduce the temperature of the mixture in Experiment 2 after 75 seconds. Show clearly on the grid how you worked out your answer. …… °C [2] (f) (i) From the results, which Experiment was the most exothermic? Explain your answer. . …… . …… [2] (ii) Compare the rates of reaction in Experiments 1 and 3. Explain why the rates of reaction are different. . …… . …… . …… [2] (g) Predict the temperature of the mixture in Experiment 2 after 2 hours. Explain your answer. . …… . …… [2] (h) When doing the experiments, what would be the advantage of taking the temperature readings every 15 seconds? . …… . …… [2] (i) Explain why a copper can should not be used in place of the polystyrene cup in these experiments. . …… . …… . …… [2] [Total: 19]

Question

Two substances, solid N and solid O were analysed. Solid N was hydrated aluminium sulfate. Tests were done on solid N and solid O. tests on solid N Complete the expected observations. (a) Describe the appearance of solid N. observation …… [1] Solid N was divided into two portions. (b) The first portion of solid N was heated in a hard-glass test-tube. Any gas produced was tested with cobalt(II) chloride paper. observations …… . …… [2] The second portion of solid N was added to distilled water. The mixture was shaken to dissolve solid N and form solution N. Solution N was divided into two equal portions in two test-tubes. (c) (i) Drops of aqueous sodium hydroxide were added to the first portion of solution N until a change was seen. observations …… [1] (ii) An excess of aqueous sodium hydroxide was then added to the mixture from (c)(i). observations …… [1] (d) Dilute nitric acid and aqueous barium nitrate were added to the second portion of solution N. observations …… [1] tests on solid O Some of the tests and observations are shown. tests on solid O observations test 1 A flame test was done on solid O. lilac flame Solid O was dissolved in water. The solution was divided into two portions. test 2 An excess of aqueous sodium hydroxide was no change added to the first portion of the solution. test 3 Dilute nitric acid and aqueous silver nitrate were white precipitate formed added to the second portion of the solution. (e) Identify solid O. . …… [2] [Total: 8]

Question

Calcium carbonate, calcium hydroxide and calcium oxide can be used to neutralise the acid in soil. Plan an investigation to find out which of these calcium compounds neutralises acid most effectively. You are provided with the three calcium compounds, dilute hydrochloric acid and common laboratory apparatus and chemicals. . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [6]