Using half reactions, write complete balanced redox equations for the following: \text { (a) } \mathrm{Mn}^{2+} / \mathrm{MnO}_{2} \text { and } \mathrm{O}_{2} / \mathrm{H}_{2} \mathrm{O} \text { (b) }

\mathrm{S}_{2} \mathrm{O}_{3}{ }^{2-} / \mathrm{SO}_{4}^{2-} \text { and } \mathrm{I}_{2} / \mathrm{\Gamma} \text { (c) } \mathrm{NH}_{4}^{+} / \mathrm{NO}_{2}^{-} \text {and } \mathrm{O}_{2} / \mathrm{H}_{2} \mathrm{O} \text { (d) } \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} / \mathrm{CO}_{2} \text { and } \mathrm{Cr}_{2} \mathrm{O}^{2}-/ \mathrm{Cr}^{3+} \text { (e) } \mathrm{CH}_{3} \mathrm{COO}^{-} / \mathrm{CO}_{2} \text { and } \mathrm{SO}_{4}{ }^{2-} / \mathrm{H}_{2} \mathrm{~S}