A second order reaction requires `70 min` to change the concentration of reactants form `0.08 M` to `0.01 M`. How much time will require to become `0.04 M` ?

Options

A. `10 min`
B. `20 min`
C. `30 min`
D. `40 min`

Answer

A

Explanation

For second order, when `(a-x) = 0.01 M`
`k_(2) = (1)/(t).(x)/(a(a-x))`
`k_(2) = (1)/(70). (0.07)/(0.08 xx 0.01)` …(i)
When `(a-x) = 0.04 M`
`k_(2) = (1)/(t).(0.04)/(0.08 xx 0.04)` …(ii)
form Eqs. (i) and (ii),
`(0.07)/(70 xx 0.08 xx 0.01) = (0.04)/(t xx 0.08 xx 0.04)`
`rArr t = 10 min`