75% of a first order reaction is completed in 30min. Calculate (a) half life, (b) rate constant and (c) time required for 99.9% completion of the reaction

Explanation

Time required for 75% completion is 2 half lifes = 30 min
(a) Half life `t-(1/2) = 15` min
(b) Rate constant (K) `0.693/t_(1//2) = 0.693/15 =- 0.046 min^(-1)`
c) Time period for 99.9% of the reaction
`t=2.303/K log a/(a-x) = 2.303/0.046 log 100/0.1 = 149` min