A first order reaction is 20% complete in 15 minutes, How much time it will take for 80% completion?

Options

A. 108.2 minutes
B. 138.6 minutes
C. 207.9 minutes
D. 60 minutes

Answer

A

Explanation

`t_(20%)=15=(2.303)/(k)log(100)/(100-20)=(2.303)/(k)log5/4` …(i)
`t_(80%)=(2.303)/(k)log(100)/(100-80)=(2.303)/(k)log 5` …...(ii)
On dividing equation (ii) by (i),
`t_(80%)=108.2` minutes.