Question

Explain the difference between instantaneous rate of a reaction and average rate of a reaction.

Answer 1

Average rate of a reaction is the change in concentration of reactants or products and the time taken for that change to occur.

Average rate = `- (Delta ["R"])/(Delta"t") = + (Delta ["P"])/(Delta "t")`

It occurs for a long interval of time. It can be determined for multistep as well as elementary reactions.

Instantaneous rate is obtained ‘when we consider the average rate at the smallest time interval dt (i.e., when t approaches zero). Hence, for an infinitesimally small dt instantaneous rate is given by

Instantaneous rate = - `("d"["R"])/"dt" = + ("d"["P"])/"dt"`

It occurs for a short span of time. It cannot be determined for multistep and elementary reaction.