Chemistry 0620/63 October/November 2023: question paper and mark scheme

Question

Hydrated aluminium chloride is a white solid. When heated very strongly, hydrated aluminium chloride produces steam, hydrogen chloride gas and aluminium oxide. Hydrogen chloride gas is toxic and aluminium oxide is a white solid. A teacher heats a sample of hydrated aluminium chloride using the apparatus shown in Fig. 1.1. hydrated A aluminium chloride heat Fig. 1.1 (a) Name the item of apparatus labelled A in Fig. 1.1. . …… [1] (b) Explain why this experiment should be carried out in a fume cupboard. . …… . …… [1] (c) The hydrated aluminium chloride has to be heated very strongly. Describe how a Bunsen burner is adjusted to make the flame as hot as possible. . …… . …… [1] (d) During the experiment, the mass of apparatus A and its contents decreases. (i) Explain why the mass decreases. . …… . …… [1] (ii) Describe what the teacher can do to be sure all the hydrated aluminium chloride reacts. . …… . …… . …… [2] (e) In a second experiment, the teacher uses the apparatus shown in Fig. 1.2 to collect the water made. hydrated aluminium chloride waste gases heat ice Fig. 1.2 (i) Explain the purpose of the ice. . …… . …… [1] (ii) The water collected is not pure. Describe a test the teacher can do to show that the water collected is not pure. State the result of the test if the water is not pure. test …… result . …… [2] [Total: 9]

Question

A student investigates the reaction between dilute hydrochloric acid and aqueous sodium hydroxide. The student does two experiments. Experiment 1 ● Fill a burette with aqueous sodium hydroxide and run some of the aqueous sodium hydroxide out of the burette so that the level is on the burette scale. ● Record the initial burette reading. ● Use a measuring cylinder to pour 25 cm3 of dilute hydrochloric acid into a conical flask. ● Stand the conical flask on a white tile. ● Add five drops of methyl orange indicator to the conical flask. ● Slowly add aqueous sodium hydroxide from the burette to the conical flask, while swirling the flask, until the solution just changes colour. ● Record the final burette reading. Experiment 2 ● Empty the conical flask and rinse it with distilled water. ● Refill the burette with aqueous sodium hydroxide. ● Record the initial burette reading. ● Use the measuring cylinder to pour 25 cm3 of dilute hydrochloric acid into the conical flask. ● Add 0.50 g of calcium carbonate powder to the conical flask and swirl the flask. ● Stand the conical flask on the white tile. ● Add five drops of methyl orange indicator to the conical flask. ● Slowly add aqueous sodium hydroxide from the burette to the conical flask, while swirling the flask, until the solution just changes colour. ● Record the final burette reading. (a) Use the burette diagrams in Fig. 2.1 and Fig. 2.2 to record the readings for Experiment 1 and Experiment 2 in Table 2.1 and complete Table 2.1. Experiment 1 0 18 1 19 2 20 initial reading final reading Fig. 2.1 Experiment 2 1 7 2 8 3 9 initial reading final reading Fig. 2.2 Table 2.1 Experiment 1 Experiment 2 final burette reading / cm3 initial burette reading / cm3 volume of aqueous sodium hydroxide added / cm3 [4] (b) State the colour change observed in the conical flask at the end-point in both experiments. (c) When 0.50 g of calcium carbonate is added to the conical flask in Experiment 2, a gas is produced. Suggest the identity of the gas. . …… [1] (d) In Experiment 2, the conical flask is rinsed with water but the burette is not rinsed with water. (i) State why there is no need to rinse the burette with water. . …… [1] (ii) Explain why the conical flask is rinsed with water. . …… . …… [1] (iii) The conical flask is not dried after being rinsed with water. State how drying the conical flask affects the volume of aqueous sodium hydroxide needed to reach the end-point. Explain your answer. . …… . …… . …… [2] (e) (i) Compare the volumes of aqueous sodium hydroxide needed to reach the end-point in Experiment 1 and Experiment 2. . …… . …… [2] (ii) Explain why different volumes of aqueous sodium hydroxide are needed in Experiment 1 and Experiment 2. . …… . …… [1] (iii) Calculate the volume of aqueous sodium hydroxide needed to reach the end-point if Experiment 2 is repeated using 0.25 g of calcium carbonate instead of 0.50 g. volume of aqueous sodium hydroxide = …… [2] (f) Describe how the reliability of the results obtained can be confirmed. . …… . …… [1] [Total: 16]

Question

A student tests two substances: solid I and solution J. Tests on solid I Solid I is chromium(III) sulfate. The student dissolves solid I in water to form solution I. The student divides solution I into three portions. Complete the expected observations. (a) To the first portion of solution I, the student adds aqueous sodium hydroxide dropwise until it is in excess. observations adding dropwise …… observations in excess …… [2] (b) To the second portion of solution I, the student adds about 1 cm3 of dilute nitric acid followed by a few drops of aqueous silver nitrate. observations …… . …… [1] (c) To the third portion of solution I, the student adds about 1 cm3 of dilute nitric acid followed by a few drops of aqueous barium nitrate. observations …… . …… [1] Tests on solution J Table 3.1 shows the tests and the student’s observations for solution J. The student divides solution J into five portions. Table 3.1 tests observations test 1 Use a glass rod to transfer one drop of the first the universal indicator paper turns red portion of solution J onto a piece of universal indicator paper. test 2 To the second portion of solution J, add a piece the piece of magnesium ribbon disappears of magnesium ribbon. and effervescence is seen Test any gas produced. the gas produces a pop when tested with a lighted splint test 3 To the third portion of solution J, add about white precipitate 1 cm3 of dilute nitric acid followed by a few drops of aqueous silver nitrate. test 4 To the fourth portion of solution J, add about no change 1 cm3 of dilute nitric acid followed by a few drops of aqueous barium nitrate. test 5 Do a flame test on the fifth portion of solution J. lilac coloured flame (d) Suggest the pH of solution J. pH = …… [1] (e) Identify the gas given off in test 2. . …… [1] (f) Identify the three ions in solution J. . …… . …… . …… [3] [Total: 9]

Question

You are asked to investigate the effect of temperature on the rate of decomposition of aqueous hydrogen peroxide. Aqueous hydrogen peroxide decomposes to make oxygen gas. hydrogen peroxide → water + oxygen The reaction is very slow unless a catalyst is added to the hydrogen peroxide. Manganese(IV) oxide is a catalyst for this reaction. Plan an investigation to find how the temperature of the aqueous hydrogen peroxide affects the rate of the catalysed reaction. Your answer should include an explanation of how your results will tell you how the rate of reaction has changed. You are provided with aqueous hydrogen peroxide, manganese(IV) oxide and common laboratory apparatus. . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [6] Notes for use in qualitative analysis Tests for anions anion test test result carbonate, CO32– add dilute acid, then test for carbon effervescence, carbon dioxide dioxide gas produced chloride, Cl – acidify with dilute nitric acid, then white ppt. [in solution] add aqueous silver nitrate bromide, Br – acidify with dilute nitric acid, then cream ppt. [in solution] add aqueous silver nitrate iodide, I– acidify with dilute nitric acid, then yellow ppt. [in solution] add aqueous silver nitrate nitrate, NO3– add aqueous sodium hydroxide, ammonia produced [in solution] then aluminium foil; warm carefully sulfate, SO42– acidify with dilute nitric acid, then white ppt. [in solution] add aqueous barium nitrate sulfite, SO32– add a small volume of acidified the acidified aqueous potassium aqueous potassium manganate(VII) manganate(VII) changes colour from purple to colourless Tests for aqueous cations cation effect of aqueous sodium hydroxide effect of aqueous ammonia aluminium, Al 3+ white ppt., soluble in excess, giving white ppt., insoluble in excess a colourless solution ammonium, NH4+ ammonia produced on warming – calcium, Ca2+ white ppt., insoluble in excess no ppt. or very slight white ppt. chromium(III), Cr3+ green ppt., soluble in excess green ppt., insoluble in excess copper(II), Cu2+ light blue ppt., insoluble in excess light blue ppt., soluble in excess, giving a dark blue solution iron(II), Fe2+ green ppt., insoluble in excess, green ppt., insoluble in excess, ppt. turns brown near surface on ppt. turns brown near surface on standing standing iron(III), Fe3+ red-brown ppt., insoluble in excess red-brown ppt., insoluble in excess zinc, Zn2+ white ppt., soluble in excess, giving white ppt., soluble in excess, giving a colourless solution a colourless solution Tests for gases gas test and test result ammonia, NH3 turns damp red litmus paper blue carbon dioxide, CO2 turns limewater milky chlorine, Cl 2 bleaches damp litmus paper hydrogen, H2 ‘pops’ with a lighted splint oxygen, O2 relights a glowing splint sulfur dioxide, SO2 turns acidified aqueous potassium manganate(VII) from purple to colourless Flame tests for metal ions metal ion flame colour lithium, Li+ red sodium, Na+ yellow potassium, K+ lilac calcium, Ca2+ orange-red barium, Ba2+ light green copper(II), Cu2+ blue-green