In the first order reaction, the concentration of the reactant is reduced to 12.5% in one hour. The half-life period of the reaction is:

Options

A. 15 min
B. 30 min
C. 20 min
D. 3 hr

Answer

C

Explanation

For a first order reaction,
`K = 2.303/t log""([A]_0)/([A]) =2.303/60log"" (100)/12.5 = 0.0346 "min"^(-1)`
Now t `1//2 = 0.693/K = 0.639/0.0346 = 20 min`.