In a first order reaction the concentration of the reactant decreases from 800 mol/ `dm^(3)` to 50 mol/ `dm^(3)` in `2xx10^(4)` sec . The rate constant of the reaction in `sec^(-1)` is :

Options

A. `2xx10^(4)`
B. `3.45xx10^(-5)`
C. `1.386xx10^(-4)`
D. `2xx10^(-4)`

Answer

C

Explanation

(C ) k = `(2.303)/(t) "log" ([A]_(0))/([A])`
`k = (2.303)/(2xx10^(4))"log" (800)/(50) = 1.38 xx10^(-4) s^(-1)`