Question

Substance Q initially weighs 120% of its remaining mass after its decay in 60 minutes. What is its half-life in hours?

Answer 1

Time = 60min = 1hr

Initial concentration= 1.2

Final concentration= 1

For first order reaction :-

$K =\frac {2.303} {t} log\frac {[initial]} {[final]}$

=> K = 0.18 hr-

Half life = $\frac {0.691} {K} =\frac {0.691} {0.18} = 3.8 hours$