Reacting gases are enclosed in a sealed cylinder fitted with a movable piston. The piston is moved outwards so that the gas pressure decreases. The temperature is kept constant.
Which statement explains why the rate of reaction decreases?
The collision frequency is unchanged, but the fraction of collisions with enough energy decreases
The collision frequency increases, but each collision has less kinetic energy
The collision frequency decreases, but the fraction of collisions with enough energy is unchanged
The collision frequency decreases, and the activation energy increases
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.