Collision Theory

Question

Explain, in terms of collision theory, how and why a reaction's rate changes as the reaction progresses.

Answer 1

A the reaction progresses, the concentrations of reactants and products changes (with time). As the concentrations change, the rate of collisions change, i.e. as concentrations decrease, collisions/unit time decrease. As collisions/unit time decrease, the rate of reaction decreases because the rate depends on the number of collisions per unit time.