Chemistry 0620/63 May/June 2023: question paper and mark scheme

Question

This question is about separating mixtures. (a) The apparatus in Fig. 1.1 can be used to separate a mixture of liquids with different boiling points. A B Fig. 1.1 (i) Name the separation technique that uses the apparatus shown in Fig. 1.1. . …… [1] (ii) Name the items of apparatus labelled A and B. A …… B …… [2] (iii) Draw an arrow on Fig. 1.1 to show where the apparatus should be heated. [1] (b) Fig. 1.2 shows the apparatus that can be used to separate insoluble calcium carbonate from aqueous sodium chloride. Fig. 1.2 (i) State the term used for the solid removed from a liquid using the apparatus shown in Fig. 1.2. . …… [1] (ii) The calcium carbonate obtained using the apparatus in Fig. 1.2 is contaminated with aqueous sodium chloride. Describe how the aqueous sodium chloride can be removed. . …… . …… [1] (iii) Name the method of separation that can be used to obtain solid sodium chloride from an aqueous solution of sodium chloride. . …… [1] [Total: 7]

Question

A student investigates the temperature change when solid citric acid reacts with solid sodium carbonate. The student does six experiments. (a) Experiment 1 ● Place 5.0 g of solid sodium carbonate in a 100 cm3 beaker. ● Use a thermometer to stir the solid sodium carbonate for 30 seconds. Measure the temperature of the solid sodium carbonate. Experiment 2 ● Add 1.0 g of solid citric acid to the solid sodium carbonate in the beaker from Experiment 1. ● Use the thermometer to stir the mixture for 30 seconds. Measure the temperature of the mixture. ● Rinse the beaker and thermometer with water. Experiment 3 ● Place 5.0 g of solid sodium carbonate in the 100 cm3 beaker. ● Add 2.0 g of solid citric acid to the solid sodium carbonate in the beaker. ● Use the thermometer to stir the mixture for 30 seconds. Measure the temperature of the mixture. ● Rinse the beaker and thermometer with water. Experiment 4 ● Repeat Experiment 3, using 4.0 g of solid citric acid instead of 2.0 g. Experiment 5 ● Repeat Experiment 4, using 5.0 g of solid citric acid instead of 4.0 g. Experiment 6 ● Repeat Experiment 5, using 6.0 g of solid citric acid instead of 5.0 g. Use the information in the description of the experiments and the thermometer diagrams to complete Table 2.1. Table 2.1 mass of mass thermometer temperature after experiment solid sodium of solid diagram after 30 seconds / °C carbonate / g citric acid / g 30 seconds 30 1 5.0 0.0 25 20 20 2 5.0 1.0 15 10 10 3 5 0 10 4 5 0 0 5 –5 –10 0 6 –5 –10 [4] (b) Complete a suitable scale on the y-axis and plot the results from Experiments 1 to 6 on Fig. 2.1. Draw a line of best fit through your points. temperature / C mass of 0 citric acid 0 1 2 3 4 5 6 /g Fig. 2.1 [4] (c) State whether the reaction between solid sodium carbonate and solid citric acid is exothermic or endothermic. Explain your answer. . …… . …… [1] (d) Deduce which experiment had the greatest temperature change compared to the temperature in Experiment 1. . …… [1] (e) From your graph, deduce the temperature, after stirring for 30 seconds, that is obtained when 3.5 g of solid citric acid is added to 5.0 g of solid sodium carbonate. Show clearly on the grid how you worked out your answer. temperature = …… °C [2] (f) Suggest why the solid sodium carbonate and solid citric acid are stirred before the temperature is measured. . …… . …… [2] (g) Explain why using a polystyrene cup in place of the glass beaker would increase the accuracy of the results. . …… . …… [2] [Total: 16] Question 3 starts on the next page.

Question

A student tests two solids: solid G and solid H. Tests on solid G Table 3.1 shows the student’s observations for solid G. Solid G contains three ions. Table 3.1 tests observations test 1 Do a flame test on solid G. lilac coloured flame test 2 Heat half of solid G in a boiling tube. solid G became a solution, condensation Hold anhydrous cobalt(II) chloride paper above formed at the top of the boiling tube; the boiling tube. cobalt(II) chloride paper turned pink test 3 Dissolve the remaining solid G in water to form solution G. Divide solution G into three portions. To the first portion of solution G, add aqueous white precipitate which dissolves in excess sodium hydroxide dropwise and then in excess. test 4 To the second portion of solution G, add a pale purple solution few drops of acidified aqueous potassium manganate(VII). test 5 To the third portion of solution G, add 1 cm3 white precipitate of dilute nitric acid followed by a few drops of aqueous barium nitrate. (a) State what conclusion can be made about solid G from the observations in test 2. . …… [1] (b) State what conclusion can be made about solid G from the observations in test 4. . …… [1] (c) The observations in test 3 show that one of two possible cations could be in solid G. Identify these two possible cations. . …… . …… [2] (d) Identify two ions, other than those you gave in (c), which must be in solid G. . …… . …… [2] Tests on solid H Solid H is copper(II) carbonate. (e) About 10 cm3 of dilute hydrochloric acid is added to solid H. Any gas given off is tested. observations …… . …… . …… [2] The solution formed in (e) is solution I. Solution I is divided into two portions. (f) To the first portion of solution I, add aqueous sodium hydroxide dropwise and then in excess. observations when added dropwise …… observations in excess …… [2] (g) To the second portion of solution I, add 1 cm3 of dilute nitric acid followed by a few drops of aqueous silver nitrate. observations …… . …… [1] [Total: 11]

Question

Oxalic acid is a white solid which is soluble in both water and ethanol to form colourless solutions. Plan an experiment to determine if oxalic acid is more soluble in water or in ethanol, at room temperature. Your answer should include how your results tell you if oxalic acid is more soluble in water or in ethanol, at room temperature. You are provided with oxalic acid, water, ethanol 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