Question

The reaction $2X\to B$ is a zeroth order reaction. If the initial concentration of $X$ is $0.2M$, the half life is $6h$. When the initial concentration of $X$ is $0.5M$, the times required to reach its final concentration of $0.2M$ will be:

• A. $18.0h$
• B. $7.2$
• C. $9.0h$
• D. $12.0h$

Answer 1

The correct option is A $18.0h$

For zero-order

$\left[A_0\right]-\left[A_1\right]=kt$

$0.2-0.1=k\times 6$

$k=\frac{1}{60}M/hr$
and $0.5-0.2=\frac{1}{60}\times t$
$t=18$ hrs.

Hence, the correct option is $A$