Question

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

Answer 1

Correct Answer - D
`t_(1//2) = 15` minute
`:. t = (2.303 xx 15)/(0.639)"log"(0.1)/(0.025) = 30 min`