The concentration of a chemical degrades according to first-order kinetics. the degradation constant is 0.2 day-1. if the initial concentration is 100.0 mg l-1, how many days are required for the concentration to reach 0.14 mg l-1?

It will require 33 days to reach concentration of the chemical equal to 0.14 mg/ L

Explanation:

For a first order reaction :

The rate law is -

Where and   are initial concentration of A and concentration of A after t time respectively. k is degradation constant or rate constant.

Here k = 0.2 , and

So plug-in all the given values in the rate equation-

or, t = 33

So, it will require 33 days to reach concentration of the chemical equal to 0.14 mg/ L