Chemistry 0620/62 February/March 2022: question paper and mark scheme

Question

Calcium carbonate reacts with dilute hydrochloric acid. The products of the reaction are aqueous calcium chloride, water and carbon dioxide gas. A student investigated the rate of the reaction between calcium carbonate and dilute hydrochloric acid using the apparatus shown. cotton wool flask dilute hydrochloric acid calcium carbonate balance 124.25 g The mass of the flask and contents was recorded every 30 seconds. When the reaction stopped there were still small pieces of calcium carbonate in the flask. (a) State what happens to the reading on the balance as the reaction takes place. Explain your answer. reading on balance …… explanation …… . …… [2] (b) There is a piece of cotton wool in the neck of the flask. (i) Suggest why a bung is not used in the neck of the flask. . …… . …… [1] (ii) Suggest why cotton wool is placed in the neck of the flask rather than leaving the flask open. . …… . …… [1] (c) State which reactant is in excess. . …… [1] (d) Describe how crystals of calcium chloride can be obtained from the mixture left in the flask after the reaction has stopped. . …… . …… . …… . …… [3] [Total: 8]

Question

A student investigated the temperature change when anhydrous lithium chloride dissolves in water. The student did six experiments. (a) Experiment 1 ● Using a measuring cylinder, 30 cm3 of distilled water was poured into a 100 cm3 beaker. ● The initial temperature of the water was measured using a thermometer. ● 1.0 g of anhydrous lithium chloride was added to the water in the beaker. At the same time a timer was started. ● The water and lithium chloride mixture was continually stirred using a thermometer. ● The temperature of the mixture was measured after 30 seconds. ● The beaker was rinsed with distilled water. Experiment 2 ● Experiment 1 was repeated using 1.5 g of anhydrous lithium chloride instead of the 1.0 g of anhydrous lithium chloride. Experiment 3 ● Experiment 1 was repeated using 2.0 g of anhydrous lithium chloride instead of the 1.0 g of anhydrous lithium chloride. Experiment 4 ● Experiment 1 was repeated using 2.5 g of anhydrous lithium chloride instead of the 1.0 g of anhydrous lithium chloride. Experiment 5 ● Experiment 1 was repeated using 3.0 g of anhydrous lithium chloride instead of the 1.0 g of anhydrous lithium chloride. Experiment 6 ● Experiment 1 was repeated using 4.0 g of anhydrous lithium chloride instead of the 1.0 g of anhydrous lithium chloride. Use the thermometer diagrams to complete the table and calculate the temperature changes. mass of initial after 30 seconds anhydrous temperature experiment change lithium chloride thermometer temperature thermometer temperature /g diagram / C diagram / C / C 30 30 1 1.0 25 25 20 20 30 30 2 1.5 25 25 20 20 30 35 3 2.0 25 30 20 25 30 35 4 2.5 25 30 20 25 30 40 5 3.0 25 35 20 30 30 40 6 4.0 25 35 20 30 [5] (b) Complete a suitable scale on the y-axis and plot the results from Experiments 1 to 6 on the grid. Draw a straight line of best fit through your points. The straight line must pass through (0,0). temperature change / C 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 mass of anhydrous lithium chloride / g [5] (c) From your graph, deduce the temperature change when 3.2 g of anhydrous lithium chloride is dissolved in 30 cm3 of distilled water. Show clearly on the grid how you worked out your answer. temperature change = …… °C [2] (d) Estimate the temperature change if Experiment 6 is repeated using 60 cm3 of water instead of 30 cm3 of water. Give a reason for your answer. . …… . …… . …… [2] (e) Suggest two changes that could be made to the apparatus to improve the accuracy of the results. For each change explain why it improves the accuracy of the results. change 1 . …… explanation 1 …… . …… change 2 . …… explanation 2 …… . …… [4] [Total: 18]

Question

Solution A and solid B were analysed. Solution A was aqueous copper(II) bromide. Tests were done on each substance. Complete the expected observations. tests on solution A Solution A was divided into three approximately equal portions in three test-tubes. (a) The end of a piece of wire was dipped into the first portion of solution A. The end of the wire was then placed at the edge of a roaring Bunsen burner flame. observations …… [1] (b) To the second portion of solution A aqueous ammonia was added dropwise until in excess. observations …… . …… . …… [3] (c) To the third portion of solution A about 1 cm depth of dilute nitric acid followed by a few drops of aqueous silver nitrate were added. observations …… . …… [1] tests on solid B tests observations Solid B was added to 15 cm of water in 3 a boiling tube. A bung was placed in the boiling tube and it was shaken to dissolve solid B and form solution B. Solution B was divided into three approximately equal portions in three test‑tubes. test 1 The first portion of solution B was tested using the universal indicator paper turned blue universal indicator paper. test 2 To the second portion of solution B aqueous a white precipitate formed which sodium hydroxide was added dropwise and remained when excess aqueous then in excess. sodium hydroxide was added test 3 To the third portion of solution B aqueous the solution remained colourless ammonia was added dropwise and then in excess. (d) Deduce the pH of solution B. pH = …… [1] (e) Identify solid B. . …… . …… [2] [Total: 8]

Question

Fizzy drinks contain carbon dioxide gas dissolved in a liquid. The carbon dioxide gas can be removed from the fizzy drink by heating. Plan an investigation to find the volume of carbon dioxide gas in 1 dm3 of a fizzy drink. Include in your answer how you will calculate the volume of carbon dioxide gas dissolved in 1 dm3 of a fizzy drink. You are provided with a small sample (less than 1 dm3) of the fizzy drink and common laboratory apparatus. (1 dm3 = 1000 cm3) . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [6]