Chapter 14, Problem 51QP

Balance the following half-reactions, adding ${\text{H}}^{+}\left(aq\right),{\text{H}}_2\text{O}\left(l\right),$ and electrons as appropriate.

$\begin{array}{l}\left(\text{a}\right)\text{ Ba}\left(s\right)\to {\text{Ba}}^{2+}\left(aq\right)\hfill \\ \left(\text{b}\right){\text{ HNO}}_{\text{2}}\left(aq\right)\to \text{NO}\left(g\right)\hfill \\ \left(\text{c}\right){\text{ H}}_{\text{2}}{\text{O}}_{\text{2}}\left(aq\right)\to {\text{H}}_{\text{2}}\text{O}\left(l\right)\hfill \\ \left(\text{d}\right){\text{ Cr}}^{3+}\left(aq\right)\to {\text{Cr}}_{\text{2}}{\text{O}}_7^{2-}\left(aq\right)\hfill \end{array}$