Write two differences between ‘order of reaction’ and ‘molecularity of reaction.'.

Ans:

Molecularity of a reaction Order of reaction
The number of reacting species which must collide simultaneously in order to bring about a chemical reaction is called molecularity of a reaction. The sum of powers of the concentrations of the reactants in the rate law expression is called the order of that chemical reaction.
Molecularity is. always a whole number value. Order may have zero, whole number, negative or fractional, values.