Chemistry · May / June 2020 · Paper 12 · Question 2

Aqueous sodium thiosulfate reacts with acid to make a precipitate of sulfur. Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + SO2(g) + S(s) A student investigates the effect of temperature on the rate of this reaction. The student: ● places a piece of paper with a cross on it below the reaction mixture as shown in the diagram ● measures the time taken for the cross to no longer be seen ● repeats the reaction at different temperatures. [diagram: paper with cross, 50 cm3 aqueous sodium thiosulfate + acid] Which apparatus is needed for this investigation?

1. Abalance, pipette, stop-clock
2. Bbalance, stop-clock, thermometer
3. Cburette, gas syringe, thermometer
4. Dmeasuring cylinder, stop-clock, thermometer

As printed in the paper