Question

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

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• A. is tripled
• B. is halved
• C. is doubled
• D. remains unchanged

Answer 1

The correct option is C is doubled

For a zero order reaction the half life will be:
$t_{1/2}=\frac{\left[R_0\right]}{2k}\dots \dots \dots \left(1\right)$
where, $\left[R_0\right]$ is the initial concentration of the reactant

After the concentration of the reactant is doubled:
$\left[R_0\right]\text{'}=2\left[R_0\right]\dots \dots \dots .\left(2\right)$

$t_{1/2}^{\prime }=\frac{[R_0{]}^{\prime }}{2k}.............\left(3\right)$

Substituting (2) in (3)
$\Rightarrow t_{1/2}^{\prime }=2\times \frac{\left[R_0\right]}{2k}$

From equation (1)
$t_{1/2}^{\prime }=2\times t_{1/2}$

Hence, after doubling the concentration of the reactant, the half life period of zero order reaction will be doubled.