Changing the concentration of the reactants
2 marks · NormalDescribe what happens to the rate of a chemical reaction when the concentration of one of the reactants is increased. Explain your answer.
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Also accept: rate increases because particles collide more often; more collisions per second cause a faster reaction
Common mistakes: Only saying 'there are more collisions' without referring to time
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Marking points
B1 · 1 mark · States that increasing concentration increases the rate of reaction.
B2 · 1 mark · Explains that there are more collisions per second/particles collide more frequently (must include time element).
Worked solution
When the concentration of a reactant is increased, the rate of the reaction increases. This is because the particles are closer together and collide more frequently (there are more collisions per second).