Imran did an experiment to see how changing the surface area of limestone affected the rate at which
it reacts with hydrochloric acid. He timed how long it
took for the reaction to produce 50 cm3 of carbon
dioxide gas. His results are shownin the picture

a) Explain why changing the surface area has the
effect that it does.

b) What must Imran have done to make this
experiment a fair test?

c) Write a word equation for this reaction (limestone
is calcium carbonate).​