For a first order reaction, (A) `rarr` products, the concentration of A changes from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M is:

Options

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

Answer

A

Explanation

`0.1 rarr 0.05 rarr 0.025`
There are two half lives involved.
Hlaf life `= (40)/(2) = 20 min`
Rate constant
`k = (0.693)/(20) = 0.347 min^(-1)`
Rate `= k[A] = 0.347 xx 0.01 = 3.47 xx 10^(-4) min^(-1)`