For a first-order reaction `A rarr B` the reaction rate at reactant concentration of `0.10 M` is found to be `2.0 xx 10^(-5) "mol" L^(-1) s^(-1)`. The half-life period of the reaction is

Options

A. 220 s
B. 30 s
C. 300 s
D. 347 s

Answer

D

Explanation

Rate, `r=k[A][because"iIt is a first order reaction"]`
`:. k=(r)/([A])=(2.0xx10^(-5)"Ms"^(-1))/(0.01M)`
`=(2xx10^(-5))/(10^(-2))s^(-1)=2xx10^(-3)s^(-1)`
`t_(1//2)=(0.693)/(k)=(0.693)/(2xx10^(-3))s`
`=346.5s ~= 347s`.