A computer model tracks collisions during a reaction. When catalyst C is added, some collisions that previously failed form products, while other collisions still fail.
Why do some collisions still fail?
Catalyst C makes particles collide less often, so fewer collisions succeed.
A collision succeeds only when the particles have exactly the activation energy.
Some collisions still have less energy than the lowered activation energy.
Catalyst C raises the activation energy needed for some collisions.
127 exam-style questions on AQA GCSE Chemistry 6.1 Rate of reaction, covering 6.1.1a Calculating rates of reactions, 6.1.1b Gradient of a tangent as rate, 6.1.2 Factors which affect the rates of chemical reactions, 6.1.3 Collision theory and activation energy, and 6.1.4 Catalysts. Each one has a worked solution and a mark scheme showing where the marks go.