Q30 / 100 · BITSAT 2023 (Memory Based Paper 1) · Chemistry
Electrode potential data are given below:
$\mathrm{Fe}^{+3}(\mathrm{aq})+\mathrm{e}^{-} \longrightarrow \mathrm{Fe}^{+2}(\mathrm{aq}) ; \mathrm{E}^{\circ}=+0.77 \mathrm{~V}$
$\mathrm{Al}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \longrightarrow \mathrm{Al}_{(\mathrm{s})} ; \mathrm{E}^{\circ}=-1.66 \mathrm{~V}$
$\mathrm{Br}_2(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{Br}^{-}(\mathrm{aq}) ; \mathrm{E}^{\circ}=+1.08 \mathrm{~V}$
Based on the data, the reducing power of $\mathrm{Fe}^{2+}$, $\mathrm{Al}$ and $\mathrm{Br}^{-}$will increase in the order
$\mathrm{Fe}^{+3}(\mathrm{aq})+\mathrm{e}^{-} \longrightarrow \mathrm{Fe}^{+2}(\mathrm{aq}) ; \mathrm{E}^{\circ}=+0.77 \mathrm{~V}$
$\mathrm{Al}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \longrightarrow \mathrm{Al}_{(\mathrm{s})} ; \mathrm{E}^{\circ}=-1.66 \mathrm{~V}$
$\mathrm{Br}_2(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{Br}^{-}(\mathrm{aq}) ; \mathrm{E}^{\circ}=+1.08 \mathrm{~V}$
Based on the data, the reducing power of $\mathrm{Fe}^{2+}$, $\mathrm{Al}$ and $\mathrm{Br}^{-}$will increase in the order
- Correct answerA$\mathrm{Br}^{-} < \mathrm{Fe}^{2+} < \mathrm{Al}$
- B$\mathrm{Fe}^{2+} < \mathrm{Al} < \mathrm{Br}^{-}$
- C$\mathrm{Al} < \mathrm{Br}^{-} < \mathrm{Fe}^{2+}$
- D$\mathrm{Al} < \mathrm{Fe}^{2+} < \mathrm{Br}^{-}$
Solution
$\begin{array}{rrrr} & \text { Fe } & \text { A1 } & \text { B } \\ E_{\text {Red }}^{\circ} & 0.77 & -1.66 & 1.08 \\ E_{\text {Oxi }}^{\circ} & -0.77 & 1.66 & -1.08\end{array}$
Hence, reducing power $\mathrm{Al}>\mathrm{Fe}^{2+}>\mathrm{Br}$
Hence, the correct answer is option: 'A'.