IGCSE Chemistry 0620 Paper 62, May/June 2023

Name the item of apparatus labelled A.

Draw an arrow on Fig. 1.1 to show where the apparatus should be heated.

Explain why powdered lead(II) oxide is used and not a large lump of lead(II) oxide.

Explain what happens at the point labelled B, on Fig. 1.1.

The waste gases contain methane. State why the waste gases should not be released into the laboratory.

Experiment 1 ● Use a $50{\text{ cm}}^3$ measuring cylinder to pour $50{\text{ cm}}^3$ of aqueous iron(III) nitrate into a $100{\text{ cm}}^3$ beaker. ● Stand the beaker on a printed sheet as shown in Fig. 2.1. ● Use a $10{\text{ cm}}^3$ measuring cylinder to pour $5{\text{ cm}}^3$ of aqueous sodium thiosulfate into the beaker and at the same time start a stop-clock. ● Use a thermometer to stir the contents of the beaker. ● Look down from above the beaker and when the text on the printed sheet becomes visible, stop the stop-clock. ● Use the thermometer to measure the temperature of the solution when the text becomes visible. ● Rinse the beaker and thermometer with water. Experiment 2 ● Use the $50{\text{ cm}}^3$ measuring cylinder to pour $50{\text{ cm}}^3$ of aqueous iron(III) nitrate into the $100{\text{ cm}}^3$ beaker. ● Heat the beaker on a gauze over a Bunsen burner until the temperature of the iron(III) nitrate has increased by about $5{}^{\circ }\text{C}$. ● Stand the beaker on the printed sheet as shown in Fig. 2.1. ● Use the $10{\text{ cm}}^3$ measuring cylinder to pour $5{\text{ cm}}^3$ of aqueous sodium thiosulfate into the beaker and at the same time start a stop-clock. ● Use the thermometer to stir the contents of the beaker. ● Look down from above the beaker and when the text on the printed sheet becomes visible, stop the stop-clock. ● Use the thermometer to measure the temperature of the solution when the text becomes visible. ● Rinse the beaker and thermometer with water. Experiment 3 ● Repeat Experiment 2, this time heating the aqueous iron(III) nitrate until the temperature has increased by about $10{}^{\circ }\text{C}$. Experiment 4 ● Repeat Experiment 2, this time heating the aqueous iron(III) nitrate until the temperature has increased by about $15{}^{\circ }\text{C}$. Experiment 5 ● Repeat Experiment 2, this time heating the aqueous iron(III) nitrate until the temperature has increased by about $25{}^{\circ }\text{C}$. Use the thermometer diagrams and stop-clock diagrams to complete Table 2.1.

Write a suitable scale on the y-axis and plot your results from Experiments 1 to 5 on Fig. 2.2. Draw a smooth curve of best fit.

Deduce the experiment in which the rate of reaction is fastest.

Use your graph to predict the temperature of the solution when the text becomes visible after 55 seconds. Show your working on Fig. 2.2. temperature = .............................. °C

Explain why wrapping the beaker in cotton wool after it has been heated will improve the accuracy of the results obtained.

Explain why it would be an improvement to measure the volume of aqueous iron(III) nitrate in a burette rather than a measuring cylinder.

Suggest why it would not be an improvement to add the aqueous sodium thiosulfate using a pipette.

Suggest why the aqueous sodium thiosulfate must be added after the aqueous iron(III) nitrate has been heated and not before it is heated.

Describe how the results of the experiment would change when the experiment is repeated using a $250{\text{ cm}}^3$ beaker in place of the $100{\text{ cm}}^3$ beaker. Explain your answer. change in results ....................................................................................................................... explanation ................................................................................................................................ ....................................................................................................................................................

Describe how to do the flame test used in test 1.

Identify the gas given off in test 2.

Identify solution F.

State what would be observed if the student adds dilute sulfuric acid to another portion of solution F. observations .............................................................................................................................. ..............................................................................................................................................

Tests on solid G Solid G is iron(II) carbonate. About $10{\text{ cm}}^3$ of dilute sulfuric acid is added to solid G. Any gas given off is tested. observations .............................................................................................................................. ....................................................................................................................................................

To the product from (e), aqueous sodium hydroxide is added dropwise until in excess. observations adding dropwise ................................................................................................... observations in excess ..............................................................................................................