A student adds excess magnesium powder to 50 cm350\,\mathrm{cm^{3}}50cm3 of dilute hydrochloric acid and measures the volume of hydrogen made.
Which change would increase the initial rate of reaction but not change the total volume of hydrogen made?
Using 50 cm350\,\mathrm{cm^{3}}50cm3 of more concentrated hydrochloric acid
Warming the hydrochloric acid before adding the magnesium
Using 100 cm3100\,\mathrm{cm^{3}}100cm3 of the same hydrochloric acid
Using the same mass of magnesium ribbon instead of powder
56 exam-style questions on OCR GCSE Chemistry 5.2 Controlling reactions, covering 5.2.1 Measuring and interpreting rate of reaction, 5.2.2 Factors affecting rate and collision theory, and 5.2.3 Catalysts, activation energy and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.