Half life of a first order reaction is 900 minute at 400 K , find its half life at 300 K ?

$$ \left(\frac{\mathrm{E}_{\mathrm{a}}}{2.303 \mathrm{R}}=1.3056 \times 10^3\right) $$

Rate law for the reaction,

$$ \mathrm{C}_2 \mathrm{H}_5 \mathrm{I}_{(\mathrm{g})} \longrightarrow \mathrm{C}_2 \mathrm{H}_{4(\mathrm{~g})}+\mathrm{HI}_{(\mathrm{g})} \text { is } \mathrm{r}=\mathrm{k}\left[\mathrm{C}_2 \mathrm{H}_5 \mathrm{I}\right] $$

What is the order and molecularity of this reaction?

For the reaction, $\mathrm{NO}_{2(\mathrm{~g})}+\mathrm{CO}_{(\mathrm{g})} \longrightarrow \mathrm{NO}_{(\mathrm{g})}+\mathrm{CO}_{2(\mathrm{~g})}$, rate of formation of $\mathrm{NO}_{(\mathrm{g})}$ is $\mathrm{Y} \mathrm{mol} \mathrm{dm} \mathrm{ds}^{-1}$. Find the rate of disappearance of $\mathrm{CO}_{(\mathrm{g})}$.

In a first order reaction concentration of reactant decreases from 20 milli $\mathrm{mol} \mathrm{dm}^{-3}$ to 8 milli $\mathrm{mol} \mathrm{dm}^{-}$ in 40 minutes, find rate constant of reaction?