Complete and balance the following half-reactions. In each case indicate whether the half-reaction is an oxidation or a reduction. $$ \begin{array}{l}{\text { (a) } \mathrm{Mo}^{3+}(a q) \longrightarrow \mathrm{Mo}(s) \text { (acidic solution) }} \\ {\text { (b) } \mathrm{H}_{2} \mathrm{SO}_{3}(a q) \longrightarrow \mathrm{SO}_{4}^{2-}(a q) \text { (acidic solution) }} \\ {\text { (c) } \mathrm{NO}_{3}^{-}(a q) \longrightarrow \mathrm{NO}(g)(\text { acidic solution })} \\ {\text { (d) } \mathrm{O}_{2}(g) \longrightarrow \mathrm{H}_{2} \mathrm{O}(l) \text { (acidic solution) }} \\ {\text { (e) } \mathrm{O}_{2}(g) \longrightarrow \mathrm{H}_{2} \mathrm{O}(l) \text { (basic solution) }} \end{array} \\\ {\text { (f) } \mathrm{Mn}^{2+}(a q) \longrightarrow \mathrm{MnO}_{2}(s) \text { (basic solution) }} \\ {\text { (g) } \mathrm{Cr}(\mathrm{OH})_{3}(s) \longrightarrow \mathrm{CrO}_{4}^{2-}(a q) \text { (basic solution) }} $$

Here are the balanced reactions: a) \( \textrm{Mo}^{3+}(aq) + 3 \, \textrm{e}^- \rightarrow \textrm{Mo}(s) \) - Reduction b) \( \textrm{H}_{2}\textrm{SO}_{3}(aq) + \textrm{H}_{2}\textrm{O} \rightarrow \textrm{SO}_{4}^{2-}(aq) + 4 \, \textrm{H}^+ + 2 \, \textrm{e}^- \) - Oxidation c) \( \textrm{NO}_{3}^{-}(aq) + 2 \, \textrm{H}^+ + \textrm{e}^- \rightarrow \textrm{NO}(g) + \textrm{H}_{2}\textrm{O} \) - Reduction d) \( \textrm{O}_{2}(g) + 4 \, \textrm{H}^+ + 4 \, \textrm{e}^- \rightarrow 2 \, \textrm{H}_{2}\textrm{O}(l) \) - Reduction e) \( 2 \, \textrm{O}_{2}(g) + 4 \, \textrm{H}_{2}\textrm{O}(l) + 4 \, \textrm{e}^- \rightarrow 4 \, \textrm{OH}^{−}(aq) \) - Reduction f) \( \textrm{Mn}^{2+}(aq) + 2 \, \textrm{OH}^-(aq) + 2 \, \textrm{e}^- \rightarrow \textrm{MnO}_{2}(s) + \, \textrm{H}_{2}\textrm{O}(l) \) - Reduction g) \( \textrm{Cr}(\textrm{OH})_{3}(s) + 5 \, \textrm{e}^- + 6 \, \textrm{OH}^-(aq) \rightarrow \textrm{CrO}_{4}^{2-}(aq) + 3 \, \textrm{H}_{2}\textrm{O}(l) \) - Reduction