A first order reaction is 20% complete in 10 min. How long it takes to complete 80% ?

Explanation

Applying first order integral rate equation, rate constant K is given as,
`k=(2.303)/(t)log.(a)/(a-x)implies(2.303)/(10)log.(100)/(100-20)=0.0223"min"^(-1)`
Time required for `80%` completion of the first order reaction, `t_(0.8)`
`t_(0.8)=(2.303)/(k)log.(100)/(100-80)=(2.303)/(0.0223)log.(100)/(20)=72.2"min"`