Chemistry 0620/52 February/March 2022: question paper and mark scheme

Question

You are going to investigate the temperature change when anhydrous lithium chloride dissolves in water. Read all of the instructions carefully before starting the experiments. Instructions You are going to do six experiments. (a) Experiment 1 ● Use a measuring cylinder to pour 30 cm3 of distilled water into a 100 cm3 beaker. ● Use a thermometer to measure the initial temperature of the water. Record the initial temperature in the table. ● Add the 1.0 g sample of anhydrous lithium chloride to the water in the beaker. At the same time start a timer. ● Continually stir the mixture in the beaker using the thermometer. ● Measure the temperature reached by the mixture after 30 seconds. Record the temperature of the mixture in the table. ● Calculate and record the temperature change in the table. ● Empty and rinse the beaker with distilled water. Experiment 2 ● Repeat Experiment 1 using the 1.5 g sample of anhydrous lithium chloride instead of the 1.0 g sample of anhydrous lithium chloride. Experiment 3 ● Repeat Experiment 1 using the 2.0 g sample of anhydrous lithium chloride instead of the 1.0 g sample of anhydrous lithium chloride. Experiment 4 ● Repeat Experiment 1 using the 2.5 g sample of anhydrous lithium chloride instead of the 1.0 g sample of anhydrous lithium chloride. Experiment 5 ● Repeat Experiment 1 using the 3.0 g sample of anhydrous lithium chloride instead of the 1.0 g sample of anhydrous lithium chloride. Experiment 6 ● Repeat Experiment 1 using the 4.0 g sample of anhydrous lithium chloride instead of the 1.0 g sample of anhydrous lithium chloride. Complete the table. mass of anhydrous initial temperature after temperature experiment lithium chloride / g temperature / °C 30 seconds / °C change / °C 1 1.0 2 1.5 3 2.0 4 2.5 5 3.0 6 4.0 [5] (b) Complete a suitable scale on the y-axis and plot your results from Experiments 1 to 6 on the grid. Draw a straight line of best fit through your points. The straight line must pass through (0,0). temperature change / C 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 mass of anhydrous lithium chloride / g [5] (c) From your graph, deduce the temperature change when 3.2 g of anhydrous lithium chloride is dissolved in 30 cm3 of distilled water. Show clearly on the grid how you worked out your answer. temperature change = …… °C [2] (d) Estimate the temperature change if Experiment 6 is repeated using 60 cm3 of water instead of 30 cm3 of water. Give a reason for your answer. . …… . …… [2] (e) Suggest two changes that could be made to the apparatus to improve the accuracy of the results. For each change explain why it improves the accuracy of the results. change 1 . …… explanation 1 …… . …… change 2 . …… explanation 2 …… . …… [4] [Total: 18]

Question

You are provided with solution A and solid B. Do the following tests on the substances, recording all of your observations at each stage. tests on solution A (a) Carry out a flame test on solution A. Record your observations. . …… [1] Divide the remaining solution A into four approximately equal portions in one boiling tube and three test‑tubes. (b) To the first portion of solution A in a boiling tube add aqueous ammonia dropwise until it is in excess. Record your observations. . …… . …… . …… [3] (c) To the second portion of solution A add about 1 cm depth of dilute nitric acid followed by a few drops of aqueous silver nitrate. Record your observations. . …… . …… [1] (d) Add the third portion of solution A to the test‑tube containing aqueous chlorine. Record your observations. . …… . …… [1] (e) To the fourth portion of solution A add the magnesium ribbon. Record your observations. . …… . …… [1] (f) Identify the three ions contained in solution A. . …… . …… . …… [3] tests on solid B Add about 15 cm3 of distilled water to the boiling tube containing solid B. Replace the stopper in the boiling tube and shake the boiling tube to dissolve as much solid B as possible and form solution B. Filter the mixture formed and collect solution B as the filtrate. Divide solution B into three approximately equal portions in three test‑tubes. (g) Test the pH of the first portion of solution B. pH = …… [1] (h) To the second portion of solution B add aqueous sodium hydroxide dropwise and then in excess. Record your observations. . …… . …… [2] (i) To the third portion of solution B add aqueous ammonia dropwise and then in excess. Record your observations. . …… . …… [1] (j) Identify solid B. . …… . …… [2] [Total: 16]

Question

Fizzy drinks contain carbon dioxide gas dissolved in a liquid. The carbon dioxide gas can be removed from the fizzy drink by heating. Plan an investigation to find the volume of carbon dioxide gas in 1 dm3 of a fizzy drink. Include in your answer how you will calculate the volume of carbon dioxide gas dissolved in 1 dm3 of a fizzy drink. You are provided with a small sample (less than 1 dm3) of the fizzy drink and common laboratory apparatus. (1 dm3 = 1000 cm3) . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [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