Question

In the first order reaction 75% of the reactant disappeared o. 1.386h . calculate the rate constant

Answer 1

Given that the reaction is first order reaction.

75% of of the reactant is disappeared.

If we assume that the initial concentration is 100 grams

Mass of reactant remaining after 1.386 hours =100-75=  25 grams.

Integrated rate law for the first order reaction is

$ln[A]_{t} = -kt+ln[A]_{o}$.

$ln25 = -k*1.386h+ln100$

3.218 =-k(1.386h)+4.605

-k(1.386h) =3.218-4.605

-k(1.386h)= -1.387

k =1.0$h^{-}$

Answer 2

This is your answer hope it helps you...