Chemistry 0620/62 February/March 2025: question paper and mark scheme

Question

Inks contain different coloured substances called dyes. A student used chromatography to investigate the coloured dyes contained in six different inks. The student drew a baseline on a sheet of chromatography paper. The student then placed a spot of each ink on the chromatography paper and set up the apparatus as shown in Fig. 1.1. The student made two errors. lid chromatography paper baseline water yellow orange green blue purple black ink ink ink ink ink ink Fig. 1.1 (a) Identify the two errors the student made. 1 …… 2 …… [2] (b) State the name of the equipment used to draw a baseline on chromatography paper. …… [1] (c) The student corrects the errors and then carries out the chromatography. The chromatogram in Fig. 1.2 shows the student’s results. yellow orange green blue purple black ink ink ink ink ink ink Fig. 1.2 (i) Identify an ink which could contain only one coloured dye. …… [1] (ii) Deduce which ink could be mixed with the blue ink to make the black ink. …… [1] (iii) Deduce the colour of one dye that is contained in all three of the orange, green and black inks. …… [1] [Total: 6]

Question

A student investigates the temperature change when aqueous copper(II) sulfate reacts separately with two different metals, zinc and iron. The student does two experiments. Experiment 1 ● Use a 50 cm3 measuring cylinder to pour 30 cm3 of aqueous copper(II) sulfate into a 100 cm3 beaker. ● Use a thermometer to measure the temperature of the contents of the beaker. This is the temperature at time = 0 s. ● Add 3 g of zinc powder to the beaker. At the same time start a stop-watch. ● Using the thermometer, continually stir the mixture in the beaker. ● Measure the temperature of the mixture every 30 seconds for 210 seconds. ● Empty and rinse the beaker with distilled water. Experiment 2 ● Repeat Experiment 1, using 3 g of iron powder instead of 3 g of zinc powder. (a) Complete Table 2.1 by using the thermometer diagrams and calculating the temperature changes from the temperature at 0 s. Table 2.1 Experiment 1 Experiment 2 temperature temperature time thermometer temperature change since thermometer temperature change since in s diagram in °C time = 0 s diagram in °C time = 0 s in °C in °C 30 30 0 24.0 0.0 22.0 0.0 20 20 40 30 30 30 20 40 30 60 30 20 50 30 90 40 20 50 30 120 40 20 50 30 150 40 20 50 30 180 40 20 50 30 210 40 20 [4] (b) Complete a suitable scale on the y-axis, and plot your results for Experiment 1 and Experiment 2 on Fig. 2.1. The point at (0, 0) has been plotted for you. Draw two curves of best fit. Both curves must start at (0, 0). Label both curves. temperature change since time = 0 s in °C 0 0 50 100 150 200 250 time in s Fig. 2.1 [5] (c) Extrapolate the curve for Experiment 1 on your graph in Fig. 2.1 to deduce the temperature change since time = 0 s in Experiment 1 after 240 seconds. Show clearly on Fig. 2.1 how you worked out your answer. temperature change = …… [3] (d) State which experiment, Experiment 1 or Experiment 2, is the more exothermic. Explain your answer. more exothermic experiment …… explanation …… [1] (e) Predict the temperature of the solution in Experiment 1 after 3 hours. temperature after 3 hours = …… °C [1] (f) Explain why using a copper container instead of the beaker would not be an improvement in this investigation. …… [1] (g) Describe two changes to the apparatus that will improve the results of this investigation. For each change, explain why it will improve the results. change 1 …… explanation 1 …… change 2 …… explanation 2 …… [4] [Total: 19]

Question

A student tests two substances: solution A and solid B. Tests on solution A Solution A is aqueous chromium(III) chloride. The student divides solution A into three approximately equal portions. Complete the expected observations. (a) To the first portion of solution A, the student adds aqueous sodium hydroxide dropwise until it is in excess. observations …… …… [2] (b) To the second 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] (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 silver nitrate. observations …… …… [1] 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 Carry out a flame test on solid B. red coloured flame test 2 Dissolve the remaining solid B in distilled water to form solution B. Divide solution B into three portions. To the first portion of solution B, add a few drops of pale purple solution acidified aqueous potassium manganate(VII). test 3 To the second portion of solution B, add about solution remains colourless 1 cm3 of aqueous sodium hydroxide. test 4 Warm the product of test 3 and test any gas given damp red litmus paper remains red off with damp red litmus paper. test 5 To the third portion of solution B, add about 1 cm3 of dilute nitric acid followed by a few drops of aqueous white precipitate barium nitrate. (d) Describe how to carry out the flame test used in test 1. …… [2] (e) Identify the ion that is tested for in test 4. …… [1] (f) Identify the two ions which are in solid B. …… [2] [Total: 9]

Question

Metal spoons can be electroplated with silver. Describe how a metal spoon can be electroplated with silver. Include in your answer how you could determine the mass of the silver electroplated onto the metal spoon. You are provided with solid silver nitrate, a metal spoon, a piece of solid silver, distilled water and common laboratory apparatus. You must include a diagram in your answer. …… [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