In a first order reaction, the concentration of the reactant decreases form `0.8 M` to `0.4 M` in `15 min`. The time taken for the concentration to change form `0.1 M` to `0.025 M` is

Options

A. 60 minutes
B. 15 minutes
C. 7.5 minutes
D. 30 minutes

Answer

D

Explanation

The concentration of reactant decreases from 0.8 to 0.4 in 15 minutes.
`therefore " "t_(1//2) =15` m in
To decrease the concentration from 0.1 to 0.025, we need two half lives i.e., 30 minutes.