Chemistry 0620/51 May/June 2020: question paper and mark scheme

Question

You are going to investigate the reaction between dilute hydrochloric acid and two different aqueous solutions of sodium carbonate labelled solution E and solution F. Read all of the instructions carefully before starting the experiments. Instructions You are going to do three experiments. (a) Experiment 1 ●● Fill the burette up to the 0.0 cm3 mark with dilute hydrochloric acid. ●● Use the measuring cylinder to pour 25 cm3 of solution E into the conical flask. ●● Add five drops of thymolphthalein indicator to the conical flask. ●● Slowly add dilute hydrochloric acid from the burette to the conical flask, while swirling the flask, until the solution just changes colour. ●● Record the burette readings in the table and complete the table. Experiment 1 final burette reading / cm3 initial burette reading / cm3 volume of dilute hydrochloric acid added / cm3 Experiment 2 ●● Empty the conical flask and rinse it with distilled water. ●● Refill the burette with dilute hydrochloric acid. ●● Repeat Experiment 1 using five drops of methyl orange indicator instead of thymolphthalein indicator. ●● Record the burette readings in the table and complete the table. Experiment 2 final burette reading / cm3 initial burette reading / cm3 volume of dilute hydrochloric acid added / cm3 Experiment 3 ●● Empty the conical flask and rinse it with distilled water. ●● Refill the burette with dilute hydrochloric acid. ●● Use the measuring cylinder to pour 25 cm3 of solution F into the conical flask. ●● Add five drops of methyl orange indicator to the conical flask. ●● Slowly add dilute hydrochloric acid from the burette to the conical flask, while swirling the flask, until the solution just changes colour. ●● Record the burette readings in the table and complete the table. Experiment 3 final burette reading / cm3 initial burette reading / cm3 volume of dilute hydrochloric acid added / cm3 [5] (b) (i) What colour change was observed in the conical flask in Experiment 1? from …… to …… [1] (ii) What colour change was observed in the conical flask in Experiment 2? from …… to …… [1] (c) Compare the volumes of dilute hydrochloric acid added in Experiment 2 and Experiment 3. Explain any difference. . …… . …… [2] (d) Determine the simplest whole number ratio of volumes of dilute hydrochloric acid used in Experiments 1 and 2. ratio Experiment 1 : Experiment 2 = …… [1] (e) What volume of dilute hydrochloric acid would be required if Experiment 3 was repeated using thymolphthalein indicator instead of methyl orange indicator? volume = …… [2] (f) The conical flask was rinsed with distilled water between each experiment. (i) Why was the conical flask rinsed? . …… . …… [1] (ii) Why does it not matter if a little distilled water is left in the flask after it has been rinsed? . …… . …… [1] (g) State two sources of error in the experiments. For each error suggest an improvement that would reduce the error. source of error 1 …… improvement 1 . …… . …… source of error 2 …… improvement 2 . …… . …… [4] [Total: 18]

Question

You are provided with two solids, solid G and solid H. Do the following tests on solid G and solid H, recording all of your observations at each stage. tests on solid G (a) Place about half of solid G in a hard‑glass test‑tube. Heat the solid gently and then strongly. Record your observations. . …… . …… . …… . …… [2] (b) (i) Place the remaining half of solid G in a boiling tube. Add about 10 cm3 of dilute sulfuric acid to the boiling tube. Test any gas produced. Keep the solution formed for use in (c). Record your observations. . …… . …… . …… . …… [4] (ii) Identify the gas produced in (b)(i). . …… [1] (c) Leave the solution from (b) to settle for three minutes. Carefully pour about half of the solution into another boiling tube. To this portion add aqueous ammonia slowly until in excess. Record your observations. . …… . …… . …… . …… [3] (d) What conclusions can you make about solid G? . …… . …… [2] tests on solid H (e) Carry out a flame test on solid H. Record your observations. . …… [1] Add solid H to about 10 cm3 of distilled water in a boiling tube. Stopper the boiling tube and shake it to dissolve solid H and form solution H. (f) Add about 1 cm depth of dilute nitric acid and a few drops of aqueous barium nitrate to solution H. Record your observations. . …… [1] (g) Identify solid H. . …… [2] [Total: 16]

Question

Cobalt, manganese and nickel are metals. They react with dilute hydrochloric acid to form hydrogen gas. Plan an investigation to find the order of reactivity of these three metals. You are provided with: ●● samples of each metal ●● dilute hydrochloric acid ●● common laboratory apparatus. Your plan must make it clear how your investigation will be a fair test and how you will use your results to place these metals in order of reactivity. . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [6] Notes for use in qualitative analysis Tests for anions anion test test result carbonate (CO32–) add dilute acid effervescence, carbon dioxide produced chloride (Cl –) acidify with dilute nitric acid, then add white ppt. [in solution] aqueous silver nitrate bromide (Br –) acidify with dilute nitric acid, then add cream ppt. [in solution] aqueous silver nitrate iodide (I–) acidify with dilute nitric acid, then add yellow ppt. [in solution] aqueous silver nitrate nitrate (NO3–) add aqueous sodium hydroxide, then ammonia produced [in solution] aluminium foil; warm carefully sulfate (SO42–) acidify, then add aqueous white ppt. [in solution] barium nitrate sulfite (SO32–) add dilute hydrochloric acid, warm sulfur dioxide produced gently and test for the presence of will turn acidified aqueous sulfur dioxide potassium manganate(VII) 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 a white ppt., insoluble in excess 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 grey-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 iron(III) (Fe3+) red-brown ppt., insoluble in excess red-brown ppt., insoluble in excess zinc (Zn2+) white ppt., soluble in excess, giving a white ppt., soluble in excess, giving a colourless solution colourless solution Tests for gases Flame tests for metal ions gas test and test result metal ion flame colour ammonia (NH3) turns damp red litmus paper blue lithium (Li+) red carbon dioxide (CO2) turns limewater milky sodium (Na+) yellow chlorine (Cl 2) bleaches damp litmus paper potassium (K+) lilac hydrogen (H2) ‘pops’ with a lighted splint copper(II) (Cu2+) blue-green oxygen (O2) relights a glowing splint sulfur dioxide (SO2) turns acidified aqueous potassium manganate(VII) from purple to colourless