Chemistry 0620/63 October/November 2022: question paper and mark scheme

Question

Hydrogen chloride is a colourless gas that is soluble in water and denser than air. Hydrogen chloride can be made by reacting sodium chloride with concentrated sulfuric acid. The diagram shows some of the apparatus a teacher used to make hydrogen chloride gas and to measure the volume of gas made. cotton A B sodium chloride concentrated sulfuric acid (a) Name the items of apparatus labelled A and B. A …… B …… [2] (b) Describe how the reaction is started after the apparatus has been set up. . …… . …… [1] (c) A student suggests the gas can be collected and its volume measured using a measuring cylinder as shown in the diagram. cotton sodium chloride concentrated sulfuric acid Explain why the volume of gas collected cannot be measured using this method. . …… . …… [1] (d) Complete the diagram to show how the hydrogen chloride gas could be collected and the volume of the gas measured. cotton sodium chloride concentrated sulfuric acid [1] (e) Hydrogen chloride is a toxic gas and concentrated sulfuric acid is corrosive. (i) Give one safety precaution that should be taken when working with hydrogen chloride gas. . …… [1] (ii) Give one safety precaution that should be taken when working with concentrated sulfuric acid. . …… [1] [Total: 7]

Question

A student investigated the rate of the reaction between sodium metabisulfite and potassium iodate at different temperatures. Five experiments were done at different temperatures. (a) Experiment 1 ● 70 cm3 of aqueous potassium iodate was measured using a 100 cm3 measuring cylinder and poured into a 250 cm3 beaker. ● 5 cm3 of aqueous starch was measured using a 10 cm3 measuring cylinder and poured into the beaker containing the aqueous potassium iodate. ● 5 cm3 of aqueous sodium metabisulfite was measured using a clean 10 cm3 measuring cylinder and poured into the beaker. At the same time a stop-clock was started. ● The mixture was stirred until a sudden colour change was seen. ● The stop-clock was stopped and the temperature of the mixture in the beaker was measured using a thermometer. ● The beaker was rinsed with distilled water. Experiment 2 ● 70 cm3 of aqueous potassium iodate was measured using a 100 cm3 measuring cylinder and poured into a 250 cm3 beaker. ● 5 cm3 of aqueous starch was measured using a 10 cm3 measuring cylinder and poured into the beaker containing the aqueous potassium iodate. ● The aqueous potassium iodate and starch mixture was warmed over a Bunsen burner until the temperature of the solution was about 35 °C. The beaker was then removed from above the Bunsen burner. ● 5 cm3 of aqueous sodium metabisulfite was measured using a clean 10 cm3 measuring cylinder and poured into the beaker. At the same time a stop-clock was started. ● The mixture was stirred until a sudden colour change was seen. ● The stop-clock was stopped and the temperature of the mixture in the beaker was measured using a thermometer. ● The beaker was rinsed with distilled water. Experiment 3 ● Experiment 2 was repeated but the aqueous potassium iodate and starch mixture was warmed until the temperature of the solution was about 40 °C. Experiment 4 ● Experiment 2 was repeated but the aqueous potassium iodate and starch mixture was warmed until the temperature of the solution was about 45 °C. Experiment 5 ● Experiment 2 was repeated but the aqueous potassium iodate and starch mixture was warmed until the temperature of the solution was about 50 °C. Use the thermometer diagrams and stop-clock diagrams to complete the table. thermometer temperature stop-clock time experiment diagram / °C diagram /s 0 seconds 20 0 1 15 45 15 5 15 10 10 minutes 30 0 40 0 2 35 45 15 5 15 30 10 30 0 45 0 3 40 45 15 5 15 35 10 30 0 50 0 4 45 45 15 5 15 40 10 30 0 55 0 5 50 45 15 5 15 45 10 30 [4] (b) Complete a suitable scale on the y-axis and plot the results from Experiments 1 to 5 on the grid. Draw a curve of best fit through your points. time taken to change colour / s 0 10 20 30 40 50 60 temperature / C [4] (c) Deduce which experiment had the fastest rate of reaction. . …… [1] (d) From your graph, deduce the time taken for the mixture to change colour at a temperature of 60.0 °C. Show clearly on the grid how you worked out your answer. time taken to change colour = …… [3] (e) Experiments are often repeated and the results compared to check that they are reliable. Suggest why this is difficult to do for these experiments. . …… . …… [1] (f) Suggest why the aqueous potassium iodate is warmed before the aqueous sodium metabisulfite is added rather than after it has been added. . …… . …… [1] (g) A polystyrene cup can be used instead of the beaker in this experiment. (i) Explain the advantage of transferring the warmed potassium iodate to a polystyrene cup rather than leaving it in the beaker. . …… . …… . …… [2] (ii) Suggest why it is not a good idea to put the aqueous potassium iodate in a polystyrene cup before it is warmed. . …… . …… [1] (h) Sketch on the grid the graph obtained when the experiments are repeated using aqueous potassium iodate of a higher concentration. [1] [Total: 18]

Question

Solid N and solution O were analysed. Solid N was zinc carbonate. tests on solid N (a) Dilute hydrochloric acid was added to a boiling tube containing solid N. Any gas produced was tested. observations …… . …… . …… [2] The mixture formed in the boiling tube in (a) was filtered. The filtrate collected was solution P. Solution P was divided into two approximately equal portions in two test-tubes. (b) To the first portion of solution P, aqueous sodium hydroxide was added gradually until it was in excess. observations …… . …… [2] (c) To the second portion of solution P, aqueous ammonia was added gradually until it was in excess. observations …… . …… [2] tests on solution O tests observations test 1 A flame test was carried out on solution O. lilac flame The remaining solution O was divided into three portions in three test-tubes. test 2 Universal indicator paper was dipped into the the universal indicator turned purple first portion of solution O. test 3 1 cm3 of dilute nitric acid and a few drops of no change aqueous silver nitrate were added to the second portion of solution O. test 4 Aqueous copper(II) sulfate was added blue precipitate dropwise and then in excess to the third portion which remained in excess of solution O. (d) Deduce the pH of solution O. pH = …… [1] (e) Identify solution O. . …… . …… [2] [Total: 9]

Question

Many fizzy drinks contain phosphoric acid. Phosphoric acid reacts with sodium hydrogencarbonate to make carbon dioxide gas. Value Coke and Kola Koola are two fizzy drinks which contain phosphoric acid as the only acid. Plan an investigation to find which of these two fizzy drinks contains the highest concentration of phosphoric acid. Include in your answer how your results will tell you which drink contains the highest concentration of phosphoric acid. You are provided with samples of both fizzy drinks, solid sodium hydrogencarbonate and common laboratory apparatus. . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [6]