A reaction that is of the first order with respect to reactant A has a rate constant `6 "min"^(-1)`. If we start with `[A] = 0.5 "mol" 1^(-1)`, when would `[A]` reach the value `0.05 mol 1^(-1)`

Options

A. `0.385` min
B. `0.15` min
C. `3` min
D. `3.84` min

Answer

A

Explanation

We know that for first order kinetics
`k=(2.303)/(t)log.(a)/(a-x)`
`(a-x)=0.05 "mol l"^(-1), 6=(2.303)/(t)log.(0.5)/(0.05)`
or `t=(2.303)/(6)log.(0.5)/(0.05)=(2.303)/(6)=0.384` min