Define average rate and instantaneous rate.

Explanation

(i) Average rate : The average rate of a reaction is defined as the rate of change of concentration of a reactant (or of a product) over a specified measurable period of time.
(ii) Instantaneous rate : Instantaneous rate of reaction gives the tendency of the reaction at a particular point of time during its course (or)
The time derivative of the concentration of a reactant (or product) converted to a positive number is called the instantaneous rate of reaction.