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

Options

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

Answer

A

Explanation

`t_(1//2) = 15 min `
` 0.025 = 0.1 ((1)/(2))^n or ( 0.025 )/( 0.1 ) = (1/2)^n or 1/4 = (1/2)^n " " therefore n=2`
time required `= 2 xx 15 = 30 `min