For $2{\mathrm{H}}_2{\mathrm{O}}_2\to 2{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2,{\mathrm{t}}_{0.5}=0.301\mathrm{hr}$ When $\left[{\mathrm{H}}_2{\mathrm{O}}_2\right]\text{ at }\mathrm{t}=0\text{ is }0.5\mathrm{M}$ initial rate is

Decomposition of H₂O₂ is a first order reaction.

$\mathrm{rate} = {\mathrm{k}}_1\left[\mathrm{A}\right]$

$\mathrm{rate}=\frac{0.693}{{\mathrm{t}}_{{\displaystyle \frac{1}{2}}}}\left[\mathrm{A}\right]$

$\mathrm{rate}=\frac{2.303\times 0.301}{0.301}[0.5]=1.1515 {\mathrm{Mhr}}^{-1}$