Chemical Kinetics Question 204
Question: A first order reaction with respect to the reactant A has a rate constant of $ 6\ {{\sec }^{-1}} $ . If we start with [A] = 0.5 mol/litre, then in what time the concentration of A becomes 0.05 mol/litre [DCE 2004]
Options:
A) 0.384 sec
B) 0.214 sec
C) 3.84 sec
D) 0.402 sec
Show Answer
Answer:
Correct Answer: A
Solution:
For the first order reaction $ t=\frac{2.303}{K}\log \frac{a}{a-x} $ Given: $ a=0.5\ mol/litre $ ; $ a-x=0.05\ ,mol/litre $
$ K=6{{\sec }^{-1}}. $
$ t=\frac{2.303}{6}\log \frac{0.5}{0.05}=\frac{2.303}{6}\log 10 $
$ =\frac{2.303}{6}=0.384\sec $ .
