The reaction `X to ` Product follows first order kinetics. In 40 minutes the concentration of X changes from 0.1 M to 0.025 M. Then the rate of reaction when concentration of X is 0.01 M will be

Options

A. `1.73 xx 10^(-4) min""^(-1)`
B. `3.47 xx 10^(-5) M min""^(-1)`
C. `3.47 xx 10^(-4) M min""^(-1)`
D. `1.73 xx 10^(-5) M min""^(-1)`

Answer

C

Explanation

In 40 minutes, the concentration is reduced to 1/4 of its original concentration
Therefore, half-life is 20 minutes. k= `(0.693 )/(t_(1//2)) = (0.693 )/( 20 min) = 0.0347 min""^(-1)`
rate ` - k [X]= 0.0347 min ^(-1) xx [ 0.01 M] = 3.47 xx 10^(-4) M min""^(-1)`