For the reaction, $3 \mathrm{I}_{(\mathrm{aq})}^{-}+\mathrm{S}_2 \mathrm{O}_{8(\mathrm{aq})}^{2-}…

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 formation of $\mathrm{I}_{3(\mathrm{aq})}^{-}$?
  1. $0.022 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{sec}^{-1}$
  2. $0.11 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{sec}^{-1}$
  3. $0.011 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{sec}^{-1}$
  4. $0.033 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{sec}^{-1}$

Solution

$\begin{aligned} & 3 \mathrm{I}_{(\mathrm{aq})}^{-}+\mathrm{S}_2 \mathrm{O}_{8(\mathrm{aq})}^{2-} \longrightarrow \mathrm{I}_{3(\mathrm{aq})}^{-}+2 \mathrm{SO}_{4(\mathrm{aq})}^{2-} \\ & \frac{\mathrm{d}\left[\mathrm{I}_3^{-}\right]}{\mathrm{dt}}=\frac{1}{2} \frac{\mathrm{d}\left[\mathrm{SO}_4^{2-}\right]}{\mathrm{dt}}=\frac{1}{2} \times 0.022=0.011 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{sec}^{-1} \end{aligned}$

Asked in: MHT CET 2021 (20 Sep Shift 2)

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