Question

Decomposition of substance $X$ follows first order reaction. Concentration of $X$ in vessel $A$ of $5L$ is $1M$ and it decrease to $0.25M$ in $8$ minutes. For the same substance in vessel $B$ of $10L$, the concentration decreases from $0.8M$ to $0.4M$. What is the time required?

• A. $4$ minutes
• B. $8$ minutes
• C. $2$ minutes
• D. $16$ minutes

Answer 1

The correct option is A $4$ minutes

$K_8=\frac{2.303}{8}log\frac{\left[1\right]}{\left[0.25\right]}$
$K_8=\frac{2.303}{8}log4$
$t=\frac{2.303}{\frac{2.303}{8}log4}log\left[\frac{0.8}{0.9}\right]$
$t=\frac{8}{0.6}\times 0.3=4$min

Hence, the correct option is A.