Define rate constant (k). Write the unit of rate constant for the following:

(i) First order reaction

(ii) Second order reaction

Rate law is defined as an experimentally determined equation that expresses the rate of a chemical reaction in terms of molar concentrations of the reactants.

Mathematically,

From the above equation, rate constant can be defined as the rate of the chemical reaction when the reactant concentration is set to unity.

For a first order reaction only x=1 and y=0

The units of k is thus follows

∴

For a second order reaction, consider as the rate law for simplicity.

The units of k is thus follows

∴