Question

When initial concentration of the reactant is doubled, the half-life period of a zero order reaction?

• A. Is tripled
• B. Is halved
• C. Remains unchanged
• D. Is doubled

Answer 1

The correct option is D Is doubled

When initial concentration of the reactant is doubled, the half-life period of a zero order reaction is doubled.
The half-life period of a zero order reaction is given by the expression
$t_{1/2}=\frac{\left[A_0\right]}{2k}$
The initial concentration of the reactant is doubled.
$[A{]}_0^{\prime }=2[A{]}_0$....(1)
$t_{1/2}^{\prime }=\frac{[A_0{]}^{\prime }}{2k}$....(2)
Substitute equation (1) in equation (2)
$t_{1/2}^{\prime }=\frac{2\left[A_0\right]}{2k}$
$t_{1/2}^{\prime }=2\times \frac{\left[A_0\right]}{2k}$
But $\frac{\left[A_0\right]}{2k}=t_{1/2}$
Hence $t_{1/2}^{\prime }=2t_{1/2}$
The half-life period of a zero order reaction is doubled.