Chemistry 0620/61 October/November 2025: question paper and mark scheme

Question

Hot concentrated hydrochloric acid reacts with solid manganese(IV) oxide to make chlorine gas. Chlorine gas is toxic and more dense than air. Concentrated hydrochloric acid is corrosive. Fig. 1.1 shows the apparatus used to make and collect a sample of chlorine gas. There is one error in the way the apparatus has been set up in Fig. 1.1. Y X HEAT Fig. 1.1 (a) Name the item of apparatus labelled X in Fig. 1.1. …… [1] (b) Identify the substance labelled Y in Fig. 1.1. …… [1] (c) Name an item of apparatus that can be used to heat X in Fig. 1.1. …… [1] (d) There is one error in the way the apparatus has been set up. Describe a change that needs to be made to the apparatus in Fig. 1.1 to correct this error. …… [1] (e) Explain why this experiment should be carried out in a fume cupboard. …… [1] [Total: 5] * 0000800000003 * DFD 3

Question

A student investigates the reaction between dilute hydrochloric acid and aqueous sodium hydroxide. The student does five experiments. Experiment 1 • Fill a burette with aqueous sodium hydroxide. • Run some of the aqueous sodium hydroxide out of the burette so that the level of the aqueous sodium hydroxide is on the burette scale. • Record the initial burette reading. • Use a volumetric pipette to add 25.0 cm3 of dilute hydrochloric acid to a conical flask. • Stand the conical flask on a white tile. • Add five drops of thymolphthalein 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. This is the end-point. • Record the final burette reading. Experiment 2 • Empty the conical flask and rinse it with distilled water. • Refill the burette with aqueous sodium hydroxide. • Run some of the aqueous sodium hydroxide out of the burette so that the level of the aqueous sodium hydroxide is on the burette scale. • Record the initial burette reading. • Use the volumetric pipette to add 25.0 cm3 of dilute hydrochloric acid to the conical flask. • Add 0.25 g of sodium hydrogencarbonate to the conical flask and swirl the flask. • Stand the conical flask on the white tile. • Add five drops of thymolphthalein 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. This is the end-point. • Record the final burette reading. Experiment 3 • Repeat Experiment 2 using 0.50 g of sodium hydrogencarbonate instead of 0.25 g. Experiment 4 • Repeat Experiment 2 using 1.00 g of sodium hydrogencarbonate instead of 0.25 g. Experiment 5 • Repeat Experiment 2 using 1.50 g of sodium hydrogencarbonate instead of 0.25 g. * 0000800000004 * DFD 4 (a) Use the information in the descriptions of Experiments 1 to 5 and the burette diagrams in Fig. 2.1 and Fig. 2.2 to complete Table 2.1. Experiment 1 Experiment 2 0 0 45 40 1 1 46 41 2 2 47 42 initial burette final burette initial burette final burette reading reading reading reading Fig. 2.1 Fig. 2.2 Table 2.1 Experiment Experiment Experiment Experiment Experiment 1 2 3 4 5 volume of dilute hydrochloric acid / cm3 mass of sodium 0.00 0.25 0.50 1.00 1.50 hydrogencarbonate / g final burette reading / cm3 36.0 24.1 13.5 initial burette reading / cm3 1.4 0.3 0.5 volume of aqueous sodium hydroxide added to reach 13.0 the end-point / cm3 [5] * 0000800000005 * DFD 5 (b) Complete a suitable scale on the y-axis and plot the results from Experiments 1 to 5 in Table 2.1 on Fig. 2.3. Draw a straight line of best fit. volume of aqueous sodium hydroxide added to reach the end-point / cm3 0 0.00 0.50 1.00 1.50 2.00 2.50 mass of sodium hydrogencarbonate / g Fig. 2.3 [4] (c) The sodium hydrogencarbonate added in Experiments 2 to 5 neutralises some of the dilute hydrochloric acid in the conical flask. The sodium hydroxide used in the titration neutralises the remaining dilute hydrochloric acid. Extrapolate the line on your graph in Fig. 2.3 and deduce the mass of sodium hydrogencarbonate needed to neutralise all of the dilute hydrochloric acid in the conical flask. Show clearly on Fig. 2.3 how you worked out your answer. mass of sodium hydrogencarbonate = …… [3] * 0000800000006 * DFD 6 (d) (i) Explain why a volumetric pipette is used rather than a measuring cylinder to measure the volume of dilute hydrochloric acid used in each experiment. …… [1] (ii) Explain why it is not possible to use a volumetric pipette instead of the burette to measure the volume of aqueous sodium hydroxide added in each experiment. …… [1] (e) The conical flask is placed on a white tile to make the colour change of the indicator at the end-point more visible. Explain why universal indicator is not a suitable indicator for this titration. …… [2] (f) Draw a line on Fig. 2.3 to show the results you would expect if the investigation was repeated using aqueous sodium hydroxide with twice the concentration. Label your line F. [2] [Total: 18] * 0000800000007 * DFD 7

Question

A student tests two solids: solid J and solid K. Tests on solid J Solid J is lithium chloride. Record the expected observations. (a) The student carries out a flame test on solid J. (i) State the colour the Bunsen burner flame becomes during the flame test. …… [1] (ii) The student uses a roaring Bunsen burner flame to carry out the flame test. State why a yellow Bunsen burner flame is not suitable for a flame test. …… [1] (b) The student dissolves the remaining solid J in distilled water to form solution J. The student divides solution J into two portions. (i) To the first portion of solution J, the student adds about 1 cm3 of dilute nitric acid followed by a few drops of aqueous silver nitrate. observations …… …… [1] (ii) To the second portion of solution J, the student adds aqueous sodium hydroxide until it is in excess. observations …… …… [1] * 0000800000008 * DFD 8 Tests on solid K Table 3.1 shows the tests and the student’s observations for solid K. Table 3.1 tests observations test 1 Heat about half of solid K in a boiling tube until there is condensation forms at the top of the no further change. boiling tube Hold anhydrous cobalt(II) chloride paper at the mouth of the anhydrous cobalt(II) chloride paper the boiling tube. changes colour from blue to pink test 2 The remaining solid K is dissolved in distilled water to form solution K. Solution K is divided into three portions. To the first portion of solution K, add aqueous ammonia a green precipitate forms dropwise and then in excess. the precipitate remains when excess aqueous ammonia is added test 3 To the second portion of solution K, add 1 cm3 of dilute a white precipitate forms nitric acid followed by a few drops of aqueous barium nitrate. test 4 To the third portion of solution K, add 3 cm3 of aqueous effervescence is seen and a green sodium carbonate. precipitate forms Test any gas given off. the gas turns limewater milky (c) State the conclusion that can be made from the observations in test 1. …… [1] (d) Two different cations can give the observations in test 2. (i) Identify the two possible cations that the observations in test 2 show could be in solid K. …… [2] * 0000800000009 * DFD 9 (ii) Describe an additional test that can be carried out on solution K to confirm which of the two cations you have identified in (d)(i) is in solid K. Explain how the result of this test shows which of these two cations is in solid K. test …… explanation …… [2] (e) Identify the gas given off in test 4. …… [1] (f) Identify the anion in solid K. …… [1] [Total: 11] * 0000800000010 * DFD 10

Question

When a solid metal is added to an aqueous salt of a less reactive metal, a reaction takes place. The reaction is exothermic, and the temperature of the reaction mixture increases. The larger the difference in reactivity of the two metals, the more exothermic the reaction. Cobalt, manganese and nickel are three metals which are all more reactive than copper and react with aqueous copper(II) sulfate. The temperature of the reaction mixture increases during each reaction. Plan an investigation to find the order of reactivity of the three metals cobalt, manganese and nickel. Your plan should include how you can use the results to find the order of reactivity of the three metals cobalt, manganese and nickel. You are provided with powdered samples of cobalt, manganese and nickel, aqueous copper(II) sulfate and common laboratory apparatus. …… [6] * 0000800000011 * DFD 11 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 * 0000800000012 * DFD 12 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