Chemistry 0620/52 February/March 2024: question paper and mark scheme

Question

You are going to investigate the reaction between aqueous sodium carbonate and two different solutions of dilute hydrochloric acid, labelled A and B. 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 dilute hydrochloric acid A. ● Rinse a conical flask with distilled water. ● Fill the burette with dilute hydrochloric acid A. Run some of the dilute hydrochloric acid out of the burette so that the level of the dilute hydrochloric acid is on the burette scale. ● Record the initial burette reading in Table 1.1. ● Use the measuring cylinder to pour 25 cm3 of aqueous sodium carbonate into the conical flask. ● Add five drops of methyl orange indicator to the conical flask. ● Stand the conical flask on a white tile. ● Slowly add dilute hydrochloric acid A from the burette to the conical flask, while swirling the flask, until the solution becomes orange. Record the final burette reading in Table 1.1. Experiment 2 ● Refill the burette with dilute hydrochloric acid A. Run some of the dilute hydrochloric acid out of the burette so that the level of the dilute hydrochloric acid is on the burette scale. ● Record the initial burette reading in Table 1.1. ● Empty the conical flask and rinse it with distilled water. ● Use the measuring cylinder to pour 25 cm3 of aqueous sodium carbonate into the conical flask. ● Add five drops of thymolphthalein indicator to the conical flask. ● Stand the conical flask on a white tile. ● Slowly add dilute hydrochloric acid A from the burette to the conical flask, while swirling the flask, until the solution becomes colourless. Record the final burette reading in Table 1.1. Experiment 3 ● Repeat Experiment 1, using dilute hydrochloric acid B instead of dilute hydrochloric acid A. Complete Table 1.1. Table 1.1 Experiment 1 Experiment 2 Experiment 3 final burette reading / cm3 initial burette reading / cm3 volume of dilute hydrochloric acid added / cm3 [5] (b) (i) State which solution of dilute hydrochloric acid, A or B, is the more concentrated. Explain your answer. more concentrated solution of dilute hydrochloric acid . …… explanation …… . …… [1] (ii) Deduce how many times more concentrated this solution of dilute hydrochloric acid is than the other solution of dilute hydrochloric acid. . …… . …… [1] (c) (i) Compare the volume of dilute hydrochloric acid A used in Experiment 1 to the volume of dilute hydrochloric acid A used in Experiment 2. . …… . …… . …… [2] (ii) Deduce the volume of dilute hydrochloric acid B required to reach the end-point if Experiment 3 is repeated using thymolphthalein indicator instead of methyl orange indicator. Use your answer to (c)(i) to help you. volume of dilute hydrochloric acid B = …… [2] (d) At the start of Experiment 3 the burette is rinsed with distilled water and then with dilute hydrochloric acid B. (i) Identify the substance removed from the burette when it is rinsed with distilled water at the start of Experiment 3. . …… [1] (ii) Describe how the result of the titration would change if the burette was not rinsed with dilute hydrochloric acid B after it had been rinsed with water. . …… . …… [1] (iii) Explain why the conical flask is not rinsed with aqueous sodium carbonate after it is rinsed with water. . …… . …… [1] (e) Explain why a white tile is used during the titration. . …… . …… [1] (f) Describe the effect on the result of warming the aqueous sodium carbonate used in Experiment 1 before carrying out the titration. Explain your answer. effect …… explanation …… [2] [Total: 17]

Question

You are provided with two solids: solid C and solid D. Do the following tests on the solids, recording all of your observations at each stage. Tests on solid C Divide solid C into two approximately equal portions in two boiling tubes. (a) Heat the first portion of solid C gently and test any gas given off with damp universal indicator paper. Record your observations. . …… . …… . …… [3] To the second portion of solid C, add about 10 cm3 of distilled water. Place a stopper in the boiling tube and shake the boiling tube to dissolve solid C and form solution C. Divide solution C into three approximately equal portions in two test-tubes and one boiling tube. (b) To the first portion of solution C in a test-tube, add about 1 cm depth of dilute nitric acid followed by a few drops of aqueous barium nitrate. Record your observations. . …… [1] (c) To the second portion of solution C in a test-tube, add about 1 cm depth of dilute nitric acid followed by a few drops of aqueous silver nitrate. Record your observations. . …… [1] (d) (i) To the third portion of solution C in a boiling tube, add about 1 cm depth of aqueous sodium hydroxide. Keep the product for use in (d)(ii). Record your observations. . …… [1] (ii) Warm the product from (d)(i) and test any gas given off. Record your observations. . …… [1] (e) Identify solid C. . …… . …… [2] Tests on solid D (f) Carry out a flame test on solid D. Record your observations. . …… . …… [1] (g) To the boiling tube containing solid D, add about 5 cm depth of dilute nitric acid. Test any gas given off. Keep the solution formed for use in (h). Record your observations. . …… . …… . …… [2] (h) Transfer about 1 cm depth of the solution formed in (g) to a test-tube. To the solution in the test-tube, add aqueous sodium hydroxide gradually until there is no further change. Record your observations. . …… . …… [2] (i) Identify three ions present in solid D. . …… . …… . …… [3] [Total: 17]

Question

When excess dilute sulfuric acid is added to solid zinc, hydrogen gas and aqueous zinc sulfate are made. Zn(s) + H2SO4(aq) → H2(g) + ZnSO4(aq) Plan an experiment to show that copper is a catalyst for this reaction. Your plan should include how the results of the experiment will show that copper is a catalyst for this reaction. You are provided with zinc powder, dilute sulfuric acid, copper powder 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