Changing the pressure on the reaction
2 marks · NormalDescribe the effect of increasing the pressure on a reaction between two gases, and link your answer to particle collisions.
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The rate of reaction increases because the gas particles are forced closer together, which makes them collide more often.
Also accept: Increasing pressure increases the rate because the particles collide more frequently.
Common mistakes: Saying only 'rate increases' with no explanation.
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Marking points
B1 · 1 mark · States that the rate of reaction increases.
B2 · 1 mark · Links the increase to more frequent collisions between gas particles.
Worked solution
When the pressure is increased in a reaction between gases, the rate of reaction increases because the particles are closer together and collide more often.