A substance decomposes by following first order kinetics. If 50% of the compound is decomposed in 120 minutes, how long will it take for 90% of the compound to decompose?

Explanation

`k=(0.693)/(t_(1//2))`
`=(0.693)/(120)=5.77xx10^(-3)" min"^(-1)`
For first order reaction,
`t=(2.303)/(k)"log"([A_(0)])/([A])`
`=(2.303)/(5.77xx10^(-3))"log 10"=399" minutes"`