In a first order reaction concentration of reactant decreases from 20 m mol to 10 m mol in 1.151 min. What is rate constant?

Which type of reaction order is followed by radioactive processes?

For the reaction, $$3 \mathrm{I}_{(\mathrm{aq})}^{-}+\mathrm{S}_2 \mathrm{O}_{8(\mathrm{aq})}^{2-} \longrightarrow \mathrm{I}_{3(\mathrm{aq})}^{-}+2 \mathrm{SO}_{4(\mathrm{aq})}^{2-}$$, rate of formation of $$\mathrm{SO}_4^{2-}$$ is $$0.022 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{sec}^{-1}$$. What is rate of formation of $$\mathrm{I}_{3(\mathrm{aq})}^{-}$$ ?

Instantaneous rate of a reaction is $$ - {1 \over 2}{{d[x]} \over {dt}} = - {{d[y]} \over {dt}} = {1 \over 2}{{d[z]} \over {dt}}$$, identify the reaction.