How does dilution affect the reaction rate?

Dilution lowers the reaction rate. A chemical reaction can only take place when reactant particles bump into each other. The rate of the chemical reaction depends on the rate at which reactants collide. The higher the concentration of a reactant is, the more likely it is to collide into other reactants and bring about a chemical change. On the other hand, dilution lowers the rate of collision and thereby lowers the rate of reaction.