An excess of magnesium ribbon is introduced into dilute hydrochloric acid, and the amount of hydrogen gas produced is recorded as the reaction continues. The reaction is exothermic. The results are plotted on a graph showing total volume ($\text{cm}^3$) against time (s), with points P, Q and R marked. Which row explains how the rate of reaction changes between points P and Q and between points Q and R?
- Abetween P and Q: the reaction temperature is increasing; between Q and R: the acid concentration is falling
- Bbetween P and Q: the reaction temperature is increasing; between Q and R: the magnesium has been used up
- Cbetween P and Q: magnesium’s surface area is decreasing; between Q and R: the acid concentration is falling
- Dbetween P and Q: magnesium’s surface area is decreasing; between Q and R: the magnesium has been used up