Dissolved reactants P and Q react together in a solution kept at constant temperature.
The concentration of P is increased while all other conditions are kept the same. The rate of reaction increases.
Which explanation for the increase in rate is correct?
More P particles are present per unit volume, so P and Q particles collide more frequently
The added P acts as a catalyst, providing a route with a lower activation energy
The added P increases the surface area of Q, exposing more Q particles for collisions
The added P raises the pressure of the liquid, forcing P and Q particles closer together
122 exam-style questions on Edexcel GCSE Chemistry 8.1 Rates of reaction, covering 8.1.1 Measuring and interpreting rates of reaction, 8.1.2 Collision theory and the factors affecting rate, and 8.1.3 Catalysts and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.