Zero order reaction means that the rate of the reaction is proportional to zero power of the concentration of reactants.

Some enzyme catalysed reactions and reactions which occur on metal surfaces are a few examples of zero order reactions. The decomposition of gaseous ammonia on a hot platinum surface is a zero order reaction at high pressure.

Integrated rate equation for zero order reaction is given by the expression

$\mathrm{k}=\frac{{\left[\mathrm{R}\right]}_{0-}{\left[\mathrm{R}\right]}_{\mathrm{t}}}{\mathrm{t}}$

Where, k=rate constant

t=time in seconds

${\left[\mathrm{R}\right]}_0$=Initial concentration of the reactants

${\left[\mathrm{R}\right]}_{\mathrm{t}}=$Concentration of the reactants after time, t.

$$\begin{gathered} \mathrm{t}=\frac{{\left[\mathrm{R}\right]}_{0-}{\left[\mathrm{R}\right]}_{\mathrm{t}}}{\mathrm{k}} \\ =\frac{0.10-0.075}{0.0030}=8.33 \mathrm{seconds} \end{gathered}$$