Chemistry 0620/63 May/June 2021: question paper and mark scheme

Question

Cobalt(II) sulfate is a soluble salt. It can be made by reacting insoluble cobalt(II) oxide with dilute sulfuric acid. A student made a sample of hydrated cobalt(II) sulfate using the following steps. step 1 step 2 step 3 A stir cobalt(II) oxide aqueous cobalt(II) sulfate B dilute sulfuric acid heat unreacted solid cobalt(II) oxide was added the mixture was the mixture was to dilute sulfuric acid stirred and heated allowed to cool (a) Name the items of apparatus labelled A and B. A …… B …… [2] (b) (i) Suggest why the mixture was heated in step 2. . …… . …… [1] (ii) Name an item of apparatus that can be used to heat the mixture in step 2. . …… [1] (c) Name the reactant which was in excess. Explain your answer. . …… . …… [1] (d) Additional steps are required to obtain pure cobalt(II) sulfate. (i) The unreacted solid is removed from the aqueous cobalt(II) sulfate. Name the process used to remove the unreacted solid. . …… [1] (ii) Describe how crystals of hydrated cobalt(II) sulfate could be made from the solution obtained in (i). . …… . …… . …… . …… [2] [Total: 8]

Question

A student investigated the rate at which hydrogen gas was made when magnesium reacted with dilute sulfuric acid. Five experiments were carried out using the apparatus shown. rubber delivery tube clamp bung inverted 100 cm3 measuring cylinder conical flask trough water Experiment 1 ● Using a measuring cylinder, 25 cm3 of dilute sulfuric acid was poured into a conical flask. ● Using a different measuring cylinder, 30 cm3 of distilled water was poured into the conical flask. ● The apparatus was set up as shown in the diagram. ● The bung was removed from the conical flask. ● A coiled length of magnesium ribbon was added to the conical flask, the bung was replaced immediately and a timer started. ● The volume of gas collected in the inverted measuring cylinder after 30 seconds was measured. Experiment 2 ● Experiment 1 was repeated using 20 cm3 of distilled water instead of 30 cm3. Experiment 3 ● Experiment 1 was repeated using 10 cm3 of distilled water instead of 30 cm3. Experiment 4 ● Experiment 1 was repeated using 5 cm3 of distilled water instead of 30 cm3. Experiment 5 ● Experiment 1 was repeated without adding any distilled water to the dilute sulfuric acid. (a) Use the information in the description of the experiments and the inverted measuring cylinder diagrams to complete the table. volume of volume of gas volume of dilute inverted measuring experiment distilled water collected in sulfuric acid / cm3 cylinder diagram / cm3 30 seconds / cm3 10 1 20 30 10 2 20 30 30 3 40 50 50 4 60 70 80 5 90 100 [4] (b) Plot the results from Experiments 1 to 5 on the grid. Draw a smooth curve of best fit. 100 80 60 volume of gas collected in 30 seconds / cm3 40 20 0 0 5 10 15 20 25 30 35 40 volume of distilled water / cm 3 [3] (c) Extrapolate (extend) the line on your graph and deduce the volume of gas that would be collected in 30 seconds if 35 cm3 of distilled water was added to the dilute sulfuric acid. …… cm3 [2] (d) The rate of reaction can be calculated using the equation shown. volume of gas collected rate of reaction = time taken to collect the gas (i) Use this equation to calculate the rate of reaction in Experiment 3. Give the units for the rate you have calculated. rate = …… units = …… [2] (ii) State which Experiment, 1, 2, 3, 4 or 5, had the highest rate of reaction. . …… [1] (e) The volume of the dilute sulfuric acid was measured using a measuring cylinder. A 25 cm3 pipette could have been used instead of a measuring cylinder. (i) State one advantage of using a 25 cm3 pipette instead of a measuring cylinder. . …… [1] (ii) State one disadvantage of using a 25 cm3 pipette instead of a measuring cylinder. . …… [1] (f) Name another item of apparatus, which can be used instead of an inverted measuring cylinder, to collect and measure the volume of gas made in the reaction. . …… [1] (g) The diagram shows a modified conical flask that could be used in this investigation. glass divider magnesium dilute sulfuric acid Explain the advantage of using this type of conical flask instead of the type used in the investigation. . …… . …… . …… [2] [Total: 17]

Question

Solid I and solid J were analysed. Solid I was chromium(III) chloride. tests on solid I Complete the expected observations. Solid I was placed in a boiling tube and about 10 cm3 of distilled water was added to the boiling tube. The mixture was shaken to dissolve solid I and form solution I. Solution I was divided into four portions in four test-tubes. (a) Aqueous sodium hydroxide was added dropwise and then in excess to the first portion of solution I. observations …… . …… . …… [2] (b) Aqueous ammonia was added dropwise and then in excess to the second portion of solution I. observations …… . …… . …… [2] (c) About 1 cm3 of dilute nitric acid followed by a few drops of aqueous silver nitrate were added to the third portion of solution I. observations …… [1] (d) About 1 cm3 of dilute nitric acid followed by a few drops of aqueous barium nitrate were added to the fourth portion of solution I. observations …… [1] tests on solid J tests observations test 1 A flame test was carried out on solid J. lilac flame The remaining solid J was placed in a boiling tube and about 10 cm3 of distilled water was added to the boiling tube. The mixture was shaken to dissolve solid J and form solution J. test 2 About 5 cm3 of dilute nitric acid was added to effervescence solution J. Any gas produced was tested. the gas turned limewater milky test 3 A few drops of aqueous silver nitrate were no visible change added to the mixture formed in test 2. (e) Identify the gas formed in test 2. . …… [1] (f) Identify solid J. . …… . …… [2] [Total: 9]

Question

The energy given out when different liquid alcohols are burned can be compared using the apparatus shown. thermometer test-tube water spirit burner liquid alcohol Describe how the apparatus shown can be used to compare the amount of energy given out by three different liquid alcohols, ethanol, propanol and butanol. Your answer should include how the results can be used to determine which fuel gives out the most energy. . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [6]