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How does reactant concentration affect the frequency of molecular collisions?

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dissociation of E–N — reaction mechanism Possible energy diagram for the dissociation of a covalent molecule, E–N, into its ions E⁺ and N⁻ (see text).

According to collision theory, the rate of a chemical reaction depends on the frequency of collisions between reacting species. Increasing the concentration of reactants directly increases the number of particles present in a given volume, which leads to a higher frequency of molecular collisions.123

Because the reaction rate is proportional to the frequency of effective collisions, increasing reactant concentration typically results in a faster reaction rate. In elementary reactions, this relationship is reflected in the rate law; for example, in a bimolecular reaction, the rate is proportional to the concentrations of both reacting substances, as higher concentrations increase the probability that these molecules will encounter one another.13

It is important to note that while higher concentrations increase the total number of collisions, only those collisions that possess sufficient activation energy and the correct spatial orientation result in a chemical change.132