JEE Main & Advanced Chemistry Chemical Kinetics / रासायनिक बलगतिकी Sample Paper Topic Test - Chemical Kinetics

A reaction that is of the first order with respect to reactant A has a rate constant \[6{{\min }^{-1}}\]. If we start with [A]\[0.5\,mol\,{{l}^{-1}},\] when would [A] reach the value \[0.05\,mol\,{{l}^{-1}}\]

A) 0.384 min

B) 0.15 min

C) 3 min

D) 3.84 min

Correct Answer: A

Solution :

We know that for first order kinetics

\[k=\frac{2.303}{t}\log \frac{a}{a-x},\left( a-x \right)=0.05mol\text{ }{{l}^{-1}}\]

\[6=\frac{2.3030}{t}\log \frac{0.5}{0.05}\]

or \[t=\frac{2.303}{6}\log \frac{0.5}{0.05}=\frac{2.303}{6}=0.384\text{ }\min \]