Q. In the first order reaction, 75% of the reactant gets disappeared in 1.386h. The rate constant of the reaction is
A) $3.0 \times 10^{- 3}s^{- 1}$
B) $2.8 \times 10^{- 4}s^{- 1}$
C) $17.2 \times 10^{- 3}s^{- 1}$
D) $1.8 \times 10^{- 3}s^{- 1}$
Explanation
(b)
for first order reaction,
$t = \frac{2.303}{k}\log\frac{\lbrack A\rbrack_{0}}{\lbrack A\rbrack}$
$k = \frac{2.303}{1.386 \times 60 \times 60}\log\frac{100}{25}$
$k = \frac{2.303 \times 0.6021}{1.386 \times 60 \times 60} = 2.8 \times 10^{- 4}s^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.