Chemistry 0620/63 October/November 2025: question paper and mark scheme

Question

A student uses the apparatus in Fig. 1.1 to show that water is formed as one of the products when a fuel is burned. The gases produced when the fuel is burned are passed through the apparatus using a suction pump. U-tube to suction pump W burning fuel ice solid X Fig. 1.1 (a) Identify the item of apparatus labelled W in Fig. 1.1. …… [1] (b) When the fuel is burned, the steam produced passes into the U-tube. Suggest why the U-tube is surrounded by ice. …… [1] (c) Water causes solid X in the U-tube to change colour. Name solid X and state the colour change seen. solid X …… colour change from …… to …… [2] . * 0000800000003 * DFD 3 The student tries to use the apparatus in Fig. 1.2 to pass the gases produced through acidified aqueous potassium manganate(VII). There is an error in the apparatus in Fig. 1.2 so that the gases produced will not pass through the acidified aqueous potassium manganate(VII). to suction pump Y burning fuel acidified aqueous potassium manganate(VII) Fig. 1.2 (d) Identify the item of apparatus labelled Y in Fig. 1.2. …… [1] (e) On Fig. 1.2, draw a circle around the error in the apparatus. [1] (f) The error in the apparatus in Fig. 1.2 is corrected. The student observes that the acidified aqueous potassium manganate(VII) changes colour from purple to colourless. Suggest why this colour change occurs. …… [1] [Total: 7] DFD 4 * 0000800000005 * DFD 5

Question

A student investigates the temperature change when a 5 cm length of coiled magnesium ribbon reacts with excess dilute sulfuric acid. The student does five experiments. Experiment 1 • Rinse a burette with distilled water and then with dilute sulfuric acid. • Fill the burette with dilute sulfuric acid. Run some of the dilute sulfuric acid out of the burette so that the level of the dilute sulfuric acid is on the 0.0 cm3 mark. • Use the burette to add 30.0 cm3 of dilute sulfuric acid to a boiling tube. • Use a thermometer to measure the initial temperature of the acid. • Record the initial temperature. • Add a coil of magnesium ribbon to the boiling tube. At the same time start a stop-watch. • Continually stir the contents of the boiling tube using the thermometer. • After 1 minute, measure the temperature of the mixture in the boiling tube. • Record this temperature. Experiment 2 • Refill the burette with dilute sulfuric acid. Run some of the dilute sulfuric acid out of the burette so that the level of the dilute sulfuric acid is on the 0.0 cm3 mark. • Use the burette to add 25.0 cm3 of dilute sulfuric acid to a new boiling tube. • Use the thermometer to measure the initial temperature of the acid. • Record the initial temperature. • Add a coil of magnesium ribbon to the boiling tube. At the same time start the stop-watch. • Continually stir the contents of the boiling tube using the thermometer. • After 1 minute, measure the temperature of the mixture in the boiling tube. • Record this temperature. Experiment 3 • Repeat Experiment 2, using 20.0 cm3 of dilute sulfuric acid instead of 25.0 cm3. Experiment 4 • Repeat Experiment 2, using 15.0 cm3 of dilute sulfuric acid instead of 25.0 cm3. Experiment 5 • Repeat Experiment 2, using 10.0 cm3 of dilute sulfuric acid instead of 25.0 cm3. * 0000800000006 * DFD 6 (a) Use the thermometer diagrams to complete Table 2.1. Table 2.1 thermometer thermometer volume of diagram for initial diagram for temperature temperature experiment dilute initial temperature temperature after 1 sulfuric acid minute increase temperature / °C after 1 minute / °C / cm3 / °C / °C / °C 30 30 1 30.0 25 25 20 20 30 40 2 25.0 25 35 20 30 30 40 3 20.0 25 35 20 30 30 40 4 15.0 25 35 20 30 30 50 5 10.0 25 45 20 40 [4] * 0000800000007 * DFD 7 (b) On Fig. 2.1, complete a suitable scale on the y-axis and plot the results from Experiments 1 to 5. Draw a line of best fit. temperature increase / °C 0.0 10.0 15.0 20.0 25.0 30.0 35.0 volume of dilute sulfuric acid / cm3 Fig. 2.1 [4] (c) Explain why the temperature increase changes as the volume of dilute sulfuric acid changes. …… [2] (d) Extrapolate the line of best fit on your graph in Fig. 2.1 to deduce the temperature increase if 33.0 cm3 of dilute sulfuric acid is used. Show clearly on Fig. 2.1 how you worked out your answer. temperature increase = …… [3] (e) The investigation is repeated using 2.5 cm lengths of coiled magnesium ribbon instead of 5 cm lengths. On Fig. 2.1, sketch a line to show the results you would expect. Label this line E. [1] * 0000800000008 * DFD 8 (f) (i) Give one reason why a burette, rather than a measuring cylinder, is used to measure the volume of the dilute sulfuric acid. …… [1] (ii) Explain why the contents of the boiling tube are stirred during each experiment. …… [1] (g) Describe one change to the apparatus that will give more accurate results. Explain your answer. change to apparatus …… explanation …… [2] [Total: 18] * 0000800000009 * DFD 9

Question

A student tests two substances: solution A and solid B. Tests on solution A Solution A is aqueous iron(III) nitrate. Record the expected observations. The student divides solution A into three approximately equal portions. (a) To the first portion of solution A, the student adds aqueous ammonia dropwise and then in excess. observations when added dropwise …… observations in excess …… [2] (b) (i) To the second portion of solution A, the student adds excess aqueous sodium hydroxide. observations …… …… [1] (ii) To the product from (b)(i), the student adds a small piece of aluminium foil. The student gently warms the mixture formed and tests any gas produced. observations …… …… [1] (iii) Identify the gas produced in (b)(ii). …… [1] (c) To the third portion of solution A, the student adds about 1 cm3 of dilute nitric acid followed by a few drops of aqueous barium nitrate. observations …… …… [1] * 0000800000010 * DFD 10 Tests on solid B Table 3.1 shows the tests and the student’s observations for solid B. Table 3.1 tests observations test 1 Do a flame test on solid B. light green flame colour test 2 Add the remaining solid B to dilute effervescence and a colourless solution forms hydrochloric acid. Test any gas produced. limewater turns milky (d) Identify the gas produced in test 2. …… [1] (e) Identify solid B. …… [2] [Total: 9] * 0000800000011 * DFD 11

Question

Duralumin is an alloy containing a mixture of the metals aluminium, copper, magnesium and manganese only. Table 4.1 gives some information about the four metals in duralumin. Table 4.1 reaction with dilute reaction with dilute metal hydrochloric acid nitric acid aluminium reacts to form a soluble salt does not react reacts very slowly at room copper does not react temperature and quickly when heated to form a soluble salt reacts quickly to form a reacts quickly to form a magnesium soluble salt soluble salt reacts quickly to form a reacts quickly to form a manganese soluble salt soluble salt Plan an investigation to find the percentage by mass of aluminium in a sample of duralumin. Your plan must include how you will calculate the percentage by mass of aluminium in duralumin. You are provided with a powdered sample of the alloy duralumin, dilute hydrochloric acid, dilute nitric acid, distilled water and common laboratory apparatus. …… [6] DFD 12 DFD 13 DFD 14 * 0000800000015 * DFD 15 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 * 0000800000016 * DFD 16 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