Chemistry 0620/52 May/June 2024: question paper and mark scheme

Question

You are going to investigate the reaction between aqueous aluminium chloride and two aqueous solutions of sodium hydroxide, solution F and solution G. Solution F and solution G have different concentrations. Read all of the instructions carefully before starting the experiments. Instructions You are going to do three experiments. (a) Experiment 1 ● Rinse a burette with distilled water and then with aqueous aluminium chloride. ● Rinse a conical flask with distilled water. ● Fill the burette with aqueous aluminium chloride. Run some of the aqueous aluminium chloride out of the burette so that the level of the aqueous aluminium chloride is on the burette scale. ● Record the initial burette reading in Table 1.1. ● Use a measuring cylinder to pour 25 cm3 of solution F into the conical flask. ● Stand the conical flask on a black or dark-coloured sheet of paper. ● Slowly add aqueous aluminium chloride from the burette to the conical flask, while swirling the flask, until the mixture in the conical flask just starts to become cloudy. ● Record the final burette reading in Table 1.1. Experiment 2 ● Refill the burette with aqueous aluminium chloride. Run some of the aqueous aluminium chloride out of the burette so that the level of the aqueous aluminium chloride is on the burette scale. ● Record the initial burette reading in Table 1.1. ● Rinse the conical flask with distilled water. ● Rinse the measuring cylinder with distilled water and then with solution G. ● Use the measuring cylinder to pour 25 cm3 of solution G into the conical flask. ● Stand the conical flask on a black or dark-coloured sheet of paper. ● Slowly add aqueous aluminium chloride from the burette to the conical flask, while swirling the flask, until the mixture in the conical flask just starts to become cloudy. ● Record the final burette reading in Table 1.1. Experiment 3 ● Refill the burette with aqueous aluminium chloride. Run some of the aqueous aluminium chloride out of the burette so that the level of the aqueous aluminium chloride is on the burette scale. ● Record the initial burette reading in Table 1.1. ● Rinse the conical flask with distilled water. ● Use the measuring cylinder to pour 25 cm3 of solution G into the conical flask. ● Add 5 drops of thymolphthalein indicator to the conical flask. ● Stand the conical flask on a white tile. ● Slowly add aqueous aluminium chloride from the burette to the conical flask, while swirling the flask, until the thymolphthalein indicator changes colour. ● Record the final burette reading in Table 1.1. Complete Table 1.1. Table 1.1 Experiment 1 Experiment 2 Experiment 3 final burette reading / cm3 initial burette reading / cm3 volume of aqueous aluminium chloride added / cm3 [5] (b) State the colour change seen at the end-point in Experiment 3. from …… to …… [1] (c) State why the conical flask is swirled as solution F is added in Experiment 1. …… [1] (d) Suggest why the conical flask is placed on black or dark-coloured paper in Experiments 1 and 2. …… [1] (e) (i) Explain why the measuring cylinder is rinsed between Experiment 1 and Experiment 2. …… [1] (ii) Explain why the measuring cylinder does not need rinsing between Experiment 2 and Experiment 3. …… [1] (f) Compare the concentration of solution F used in Experiment 1 with the concentration of solution G used in Experiment 2. Explain your answer. …… [3] (g) Calculate the volume of aqueous aluminium chloride required when Experiment 1 is carried out with 10 cm3 of aqueous sodium hydroxide instead of 25 cm3. …… [2] (h) In all three experiments it is more accurate to measure the volume of the aqueous sodium hydroxide using a volumetric pipette instead of a measuring cylinder. Explain why it is not possible to use a volumetric pipette to measure the volume of aqueous aluminium chloride in these experiments. …… [1] [Total: 16]

Question

You are provided with two substances: solid H and solid I. Do the following tests on the substances, recording all of your observations at each stage. Tests on solid H (a) (i) Add about 10 cm3 of dilute hydrochloric acid to the sample of solid H in the boiling tube. Test any gas produced. Keep the solution produced for use in (b), (c), (d) and (e). Record your observations. …… [3] (ii) Identify the gas made in (a)(i). …… [1] The solution produced in (a)(i) is solution J. Divide solution J into four approximately equal portions in four test-tubes. (b) Carry out a flame test on the first portion of solution J. Record your observations. …… [1] (c) (i) To the second portion of solution J, add a few drops of acidified aqueous potassium manganate(VII). Record your observations. …… [1] (ii) State what conclusion can be made from the result in (c)(i). …… [1] (d) To the third portion of solution J, add a few drops of dilute sulfuric acid. Record your observations. …… [1] (e) To the fourth portion of solution J, add about 1 cm depth of dilute nitric acid followed by a few drops of aqueous barium nitrate. Record your observations. …… [1] (f) Identify solid H. …… [2] Tests on solid I Add about 5 cm depth of distilled water to the sample of solid I in the boiling tube. Replace the stopper in the boiling tube and shake to dissolve and form solution I. Divide solution I into three approximately equal portions in two boiling tubes and one test-tube. (g) To the first portion of solution I in a boiling tube, add about 2 cm depth of aqueous sodium hydroxide and warm the mixture. Test any gas produced, using damp red litmus paper and damp blue litmus paper. Record your observations. damp red litmus paper …… damp blue litmus paper …… [2] (h) (i) To the second portion of solution I in a boiling tube, add about 1 cm depth of dilute nitric acid followed by a few drops of aqueous silver nitrate. Keep the product for use in (h)(ii). Record your observations. …… [1] (ii) To the product from (h)(i), add about 4 cm depth of aqueous ammonia. Place a stopper in the boiling tube and shake to mix. Pour the product away and rinse the boiling tube and bung as soon as you have made your observations. Record your observations. …… [1] (i) Test the pH of the third portion of solution I. pH = …… [1] (j) Identify solid I. …… [2] [Total: 18]

Question

Bismuth is a metal that has a reactivity similar to that of copper. The ore bismite contains the compound bismuth(III) oxide, Bi2O3. Bismuth(III) oxide is insoluble in water and reacts with dilute acids to form an aqueous solution of a salt. The ore bismite contains no other compounds that are insoluble in water and no other compounds that react with acids to form aqueous solutions. Describe how you could obtain a sample of bismuth metal starting with a large lump of the ore bismite. You have access to common laboratory apparatus and chemicals. …… [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