A reaction whose rate depends on the reactant concentration raised to the first power is called a first order reaction. First order reaction is A → product. Rate law can be expressed as, Rate = k [A]1 . Where, k is the first order rate constant

Integrate the above equation (I) between the limits of time t = 0 and time equal to t, while the concentration varies from initial concentration [A0] to [A] at the later time.

This equation (2) is in natural logarithm. To convert it into usual logarithm with base 10, we have to multiply the term by 2.303
