Changing the surface area of the reactants
3 marks · EasyA student compares the reaction between calcium carbonate and hydrochloric acid using two forms of calcium carbonate: large lumps and powdered. All other conditions are kept the same.
State which form will react faster.
Explain why this form reacts faster.
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(a) Powdered calcium carbonate
(b) The powdered form has a greater surface area exposed to the acid, so more particles can react at the same time, increasing the frequency of collisions and making the reaction faster.
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Marking points
B1 (a) · 1 mark · Correctly identifies powdered calcium carbonate as the faster-reacting form.
M1 (b) · 1 mark · Mentions increased surface area or more particles exposed.
M2 (b) · 1 mark · Links increased surface area to more frequent collisions or faster reaction.
Worked solution
a) Powdered calcium carbonate reacts faster.
b) Powder has a larger surface area, exposing more particles to collide with the acid. More collisions occur per second, so the reaction is faster.