Find the average rate of formation of $$\mathrm{NO}_{2(\mathrm{~g})}$$, in following reaction.

$$\begin{aligned} & 2 \mathrm{~N}_2 \mathrm{O}_{5(\mathrm{~g})} \rightarrow 4 \mathrm{NO}_{2(\mathrm{~g})}+\mathrm{O}_{2(\mathrm{~g})} \\ & {\left[-\frac{\Delta\left[\mathrm{N}_2 \mathrm{O}_5\right]}{\Delta \mathrm{t}}\right]=x \mathrm{~mol} \mathrm{~dm}^{-3} \mathrm{~s}^{-1}} \end{aligned}$$

Calculate the rate constant for the first order reaction, $$\mathrm{A} \rightarrow \mathrm{B}$$ if the rate of reaction is $$5.4 \times 10^{-6} \mathrm{~mol} \mathrm{~dm}^{-3} \mathrm{~s}^{-1}$$ and $$[\mathrm{A}]=0.3 \mathrm{M}$$.

Time required for $$90 \%$$ completion of a first order reaction is '$$x$$' minute. Calculate the time required to complete $$99.9 \%$$ of the reaction at same temperature.

For the reaction, $$3 \mathrm{~I}+\mathrm{S}_2 \mathrm{O}_8^{2-} \rightarrow \mathrm{I}_3^{-}+2 \mathrm{SO}_4^{2-}$$, at a particular time $$\mathrm{t}, \frac{\mathrm{d}\left[\mathrm{SO}_4^{2-}\right]}{\mathrm{dt}}$$ is $$2.2 \times 10^{-2} \mathrm{~mol} \mathrm{~dm}^{-3} \mathrm{~s}^{-1}$$. What is the value of $$-\frac{\mathrm{d}\left[\mathrm{I}^{-}\right]}{\mathrm{dt}}$$ ?