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Comprehension \( \quad: \mathrm{E}_{\mathrm{RP}}^{\circ} \) and their respective half reactions for some change are given below;
(i)
\[
\begin{array}{l}
\mathrm{Mn}^{7+}(\mathrm{aq})+8 \mathrm{H}^{+}+5 \mathrm{e}^{-} \longrightarrow \mathrm{Mn}^{2+}(\mathrm{aq})+4 \mathrm{H}_{2} \mathrm{O}(l) \\
\mathrm{E}^{\circ}=+1.52 \mathrm{~V}
\end{array}
\]
(ii)
\[
\begin{array}{l}
\mathrm{Mn}^{7+}(\mathrm{aq})+4 \mathrm{H}^{+}+3 \mathrm{e}^{-} \longrightarrow \mathrm{MnO}_{2}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{O}(l) \\
\mathrm{E}^{\circ}=+2.26 \mathrm{~V}
\end{array}
\]
(iii)
\[
\begin{array}{l}
\mathrm{Mn}^{7+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Mn}^{5+}(\mathrm{aq}) ; \mathrm{E}^{\circ}=+0.56 \mathrm{~V} \text { (acid } \\
\text { med.) }
\end{array}
\]
(iv) \( \mathrm{Mn}^{3+}+\mathrm{e}^{-} \longrightarrow \mathrm{Mn}^{2+} ; \mathrm{E}^{\circ}=+1.51 \mathrm{~V} \) (acid med.)
(v) \( \mathrm{Mn}^{4+}+\mathrm{e}^{-} \longrightarrow \mathrm{Mn}^{3+} ; \mathrm{E}^{\circ}=+0.95 \mathrm{~V} \) (acid med.)
The most stable oxidation state of \( \mathrm{Mn} \) is
(a) \( \mathrm{Mn}^{4+} \)
(b) \( \mathrm{Mn}^{2+} \)
(c) \( \mathrm{Mn}^{7+} \)
(d) \( \mathrm{Mn}^{6+} \)
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