Question

A second order reaction is 50% complete in 15 min. How long after the start of the 10 reaction will it be 85% complete?

Answer 1

Answer: 85 minutes

Step-by-step explanation:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

Half life for second order kinetics is given by:

`t_{(1)/(2)=(1)/(k* a_0)`

`t_{(1)/(2)` = half life = 15 min

k = rate constant =?

`a_0` = initial concentration = 100 (say)

`15min=(1)/(k* 100)`

`k=(1)/(1500)`

Integrated rate law for second order kinetics is given by:

`(1)/(a)=kt+(1)/(a_0)`

a= concentration left after time t =
`100-\farc{85}{100}* 100=15`

`(1)/(15)=(1)/(1500)* t+(1)/(100)`

`t=85min`

Thus after 85 minutes after the start of the reaction, it will be 85% complete.