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 $$-\frac{\mathrm{d}\left[\mathrm{I}^{-}\right]}{\mathrm{dt}}$$ ?

What is the half life of a first order reaction if rate constant is $$4.2 \times 10^{-2}$$ per day?

The reaction, $$3 \mathrm{ClO}^{-} \rightarrow \mathrm{ClO}_3^{-}+2 \mathrm{Cl}^{-}$$ occurs in two steps:

i. $$\quad 2 \mathrm{ClO}^{-} \rightarrow \mathrm{ClO}_2^{-}+\mathrm{Cl}^{-}$$

ii. $$\quad \mathrm{ClO}_2^{-}+\mathrm{ClO}^{-} \rightarrow \mathrm{ClO}_3^{-}+\mathrm{Cl}^{-}$$,

the reaction intermediate is:

Calculate the rate constant of first order reaction if the concentration of the reactant decreases by $$90 \%$$ in 30 minutes.