Chemistry 0620/61 October/November 2023: question paper and mark scheme

Question

A student uses chromatography to analyse samples of three different dyes. The apparatus the student uses is shown in Fig. 1.1. lid paper beaker baseline Fig. 1.1 (a) A spot of each dye is placed on the paper and some ethanol is poured into the beaker. Draw on Fig. 1.1: three spots (●) to show where the three dyes are placed on the paper at the start of the ● experiment ● a line to show the level of ethanol in the beaker at the start of the experiment. [2] (b) During the experiment the ethanol moves up the paper. State when the student should remove the chromatography paper from the ethanol in the beaker. …… [1] (c) Fig. 1.2 shows the result of the chromatography experiment. dye dye dye 1 2 3 Fig. 1.2 State what conclusions can be made from this result. …… [2] [Total: 5]

Question

Copper(II) carbonate reacts with dilute acids to make carbon dioxide gas. Malachite is a mineral that contains copper(II) carbonate. A student investigates the rate of reaction between powdered malachite and dilute ethanoic acid at different temperatures. The student does six experiments. Experiment 1 ● Use a measuring cylinder to pour 40 cm3 of dilute ethanoic acid into a conical flask. ● Warm the dilute ethanoic acid by about 5 °C. ● Measure the temperature of the acid using a thermometer. ● Set the apparatus up as shown in Fig. 2.1. rubber delivery tube clamp bung inverted 100 cm3 measuring cylinder conical flask trough dilute ethanoic acid water Fig. 2.1 ● Remove the bung from the conical flask and add 1.0 g of powdered malachite to the conical flask, replace the bung and start a stop-clock. ● Record the time taken for 100 cm3 of gas to be collected in the measuring cylinder. ● Empty the conical flask and rinse it with distilled water. Experiment 2 ● Repeat Experiment 1 but warm the dilute ethanoic acid by about 10 °C. Experiment 3 ● Repeat Experiment 1 but warm the dilute ethanoic acid by about 15 °C. Experiment 4 ● Repeat Experiment 1 but warm the dilute ethanoic acid by about 25 °C. Experiment 5 ● Repeat Experiment 1 but warm the dilute ethanoic acid by about 35 °C. Experiment 6 ● Repeat Experiment 1 but warm the dilute ethanoic acid by about 40 °C. (a) Use the thermometer and stop-clock diagrams to complete Table 2.1. Table 2.1 temperature of time taken to thermometer experiment ethanoic acid stop-clock diagram collect 100 cm3 diagram / C of gas / s 0 30 seconds 0 1 25 45 15 5 15 10 20 minutes 30 0 35 0 2 30 45 15 5 15 10 25 30 0 40 0 3 35 45 15 5 15 10 30 30 0 50 0 4 45 45 15 5 15 10 40 30 0 55 0 5 50 45 15 5 15 10 45 30 0 60 0 6 55 45 15 5 15 10 50 30 [5] (b) Complete a suitable scale on the y-axis and plot the results from Experiments 1 to 6 on Fig. 2.2. Draw a line of best fit through your points. time taken to collect 100 cm3 of gas / s 0 20 30 40 50 60 70 temperature of ethanoic acid / C Fig. 2.2 [4] (c) The average rate of reaction in an experiment can be calculated using the equation shown. volume of gas collected average rate of reaction = time taken to collect the gas (i) Use this equation to calculate the average rate of reaction in Experiment 6. Give the units for the rate you have calculated. average rate = …… units …… [2] (ii) Deduce in which experiment, 1, 2, 3, 4, 5 or 6, the rate of reaction is greatest. . …… [1] (d) Extend the line on your graph in Fig. 2.2. Deduce the time taken to collect 100 cm3 of gas when the temperature of the ethanoic acid is 65 °C. Show clearly on Fig. 2.2 how you worked out your answer. …… s [3] (e) The 40 cm3 of ethanoic acid used in each experiment is measured using a measuring cylinder. Measuring cylinders are available in the following sizes. 10 cm3 25 cm3 50 cm3 100 cm3 500 cm3 Draw a circle around the size of measuring cylinder which would be most suitable to measure 40 cm3 of ethanoic acid. [1] (f) Most of the gas collected in the measuring cylinder is air rather than carbon dioxide. (i) Explain why air is collected in the measuring cylinder. . …… . …… [1] (ii) Explain why this does not affect the accuracy of the results. . …… . …… [1] (g) During each experiment the temperature of the acid decreases slowly. Give a reason why the temperature of the acid decreases and suggest a change to the apparatus used that would minimise the decrease in temperature. reason temperature decreases …… change to apparatus . …… [2] [Total: 20]

Question

A student tests two substances: solid M and solid N. Tests on solid M Solid M is hydrated chromium(III) nitrate. Complete the expected observations. (a) The student places half of solid M in a boiling tube and heats it strongly. (i) The student holds a piece of anhydrous cobalt(II) chloride paper at the mouth of the boiling tube. observations …… . …… [1] (ii) The student inserts a glowing splint into the mouth of the boiling tube. The splint bursts into flames. Identify the gas given off by heating solid M which causes this result. . …… [1] (b) The student dissolves the remaining solid M in water to form solution M. (i) The student adds aqueous sodium hydroxide dropwise and then in excess to solution M. observations adding dropwise …… observations in excess …… [2] (ii) The student adds a piece of aluminium foil to the product from (b)(i). The mixture is then warmed. The student tests for any gas produced. observations …… . …… . …… [1] Tests on solid N Table 3.1 shows the tests and the student’s observations for solid N. Table 3.1 tests observations test 1 Do a flame test on solid N. light green flame test 2 Dissolve the remaining solid N in water to form solution N. Divide solution N into four portions. To the first portion of solution N, add dilute white precipitate sulfuric acid. test 3 To the second portion of solution N, add about pale yellow precipitate 1 cm3 of dilute nitric acid followed by a few drops of aqueous silver nitrate. test 4 To the third portion of solution N, add about no visible change 1 cm3 of dilute nitric acid followed by a few drops of aqueous barium nitrate. test 5 To the fourth portion of solution N, add about brown solution 1 cm3 of aqueous chlorine. (c) Describe how to carry out a flame test. …… [2] (d) Identify solid N. …… [2] [Total: 9]

Question

Greaseaway and Kitchenclean are two solutions used as household cleaners that contain aqueous ammonia. Plan an investigation to find which of the two household cleaners contains aqueous ammonia with the highest concentration. Assume that aqueous ammonia is the only alkali in the cleaners. Include in your plan: ● the method you will use ● how your results will be used to determine which household cleaner contains aqueous ammonia with the highest concentration. You are provided with common laboratory apparatus and chemicals. …… [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