In a first order reaction, the concentration of the reactant decreases form `800 "mol dm"^(-3)` to `50 "mol dm"^(-3)` in `2 xx 10^(4) s`. The rate constant of the reaction (in `s^(-1)`) is

Options

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

Answer

C

Explanation

`K=(2.303)/(t) log ""([A]_(0))/([A]_(t)) ` [ for first order reaction ]
substituting the given values , we have
` K= (2.303)/(2xx10^(4))log""(800)/(50)=1.386xx10^(-4)sec^(-1)`