Chemistry 0620/53 May/June 2019: question paper and mark scheme

Question

You are going to investigate the temperature changes when two different metals, zinc and magnesium, react with aqueous copper(II) sulfate. Read all the instructions carefully before starting the experiments. Instructions You are going to do three experiments. (a) Experiment 1 ●● Put the cup provided into the 250 cm3 beaker for support. ●● Use the measuring cylinder to pour 25 cm3 of aqueous copper(II) sulfate into the cup. ●● Measure the initial temperature of the solution and start the timer. ●● Measure the temperature of the solution at 30 seconds and at 60 seconds. ●● Record the temperatures in the table. ●● At 60 seconds, add all of the zinc powder to the aqueous copper(II) sulfate. Stir the mixture continuously with the thermometer. ●● Continue to stir the mixture and measure the temperature of the mixture every 30 seconds for a total of 180 seconds. ●● Record your results in the table. ●● Empty the cup and rinse it with distilled water. time / s 0 30 60 90 120 150 180 temperature of mixture / °C [2] (b) Experiment 2 ●● Repeat Experiment 1 but using magnesium powder instead of zinc powder. ●● Record your results in the table. time / s 0 30 60 90 120 150 180 temperature of mixture / °C [2] (c) Experiment 3 ●● Repeat Experiment 1 but using zinc granules instead of zinc powder. ●● Record your results in the table. time / s 0 30 60 90 120 150 180 temperature of mixture / °C [1] (d) Plot your results for Experiments 1–3 on the grid. Draw three smooth line graphs. Clearly label your lines. 90 80 70 60 50 temperature of mixture / °C 40 30 20 10 0 0 30 60 90 120 150 180 time / s [3] (e) From your graph, deduce the temperature of the mixture in Experiment 2 after 75 seconds. Show clearly on the grid how you worked out your answer. …… °C [2] (f) (i) From your results, which experiment was the most exothermic? Explain your answer. . …… . …… [2] (ii) Compare the rates of reaction in Experiments 1 and 3. Explain why the rates of reaction are different. . …… . …… . …… [2] (g) Predict the temperature of the mixture in Experiment 2 after 2 hours. Explain your answer. . …… . …… [2] (h) When doing the experiments, what would be an advantage of taking the temperature readings every 15 seconds? . …… . …… [2] (i) Explain why a copper can should not be used in place of the cup in these experiments. . …… . …… [1] [Total: 19] Question 2 starts on the next page.

Question

You are provided with solid M, which is a salt. Do the following tests on solid M, recording all of your observations at each stage. tests on solid M (a) Describe the appearance of solid M. . …… [1] Use a spatula to divide solid M into two approximately equal portions. (b) Heat the first portion of solid M in a hard‑glass test-tube. Test any gas produced with cobalt(II) chloride paper. Record your observations. . …… . …… . …… [4] Add the second portion of solid M to about 10 cm3 of distilled water in a boiling tube. Stopper the boiling tube and shake the mixture to dissolve solid M and form solution M. Divide solution M into three approximately equal portions in three test-tubes. (c) (i) Add drops of aqueous sodium hydroxide to the first portion of solution M. Record your observations. . …… [2] (ii) Now add an excess of aqueous sodium hydroxide to the mixture from (c)(i). Record your observations. . …… [1] (d) (i) Add drops of aqueous ammonia to the second portion of solution M. Record your observations. . …… [1] (ii) Now add an excess of aqueous ammonia to the mixture from (d)(i). Record your observations. . …… [1] (e) Add a few drops of dilute nitric acid and about 1 cm3 of aqueous barium nitrate to the third portion of solution M. Record your observations. . …… [2] (f) What does the test in (b) tell you about solid M? . …… [1] (g) Identify solid M. . …… . …… [2] [Total: 15]

Question

Calcium carbonate, calcium hydroxide and calcium oxide can be used to neutralise the acid in soil. Plan an investigation to find out which of these calcium compounds neutralises acid most effectively. You are provided with the three calcium compounds, dilute hydrochloric acid and common laboratory apparatus and chemicals. . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [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