Hello ,

Order of a chemical reaction is the sum of the powers to which the concentration terms are raised for expressing the rate law.

Characteristics of the Order of a reaction :

1. The order of a reaction maybe -ve integer, +ve integer , zero or fraction.
2. It is an experimental factor
3. It can be taken from balance equation of the reaction if it is elementary ( single step) reaction otherwise the slowest step of the mechanism gives the rate law and order of reaction.