Chemistry · May / June 2019 · Paper 12 · Question 18

An experiment is carried out to measure the rate of reaction between magnesium and dilute hydrochloric acid under two different conditions. The mass of magnesium and the number of moles of hydrochloric acid are the same in both experiments. Graphs of the results are shown. [graph: volume of gas produced / cm³ against time / s, curves 1 and 2] Which statements could explain the difference between graph 1 and graph 2? 1 Graph 1 results are obtained at a higher temperature. 2 Graph 1 results are obtained by using hydrochloric acid that is more concentrated. 3 Graph 1 results are obtained using smaller pieces of magnesium.

1. A1, 2 and 3
2. B1 and 2 only
3. C1 and 3 only
4. D2 and 3 only

As printed in the paper