4.2 Exercise 30

Balance each of the following equations according to the half-reaction method:

(a) $\text{MnO}_{4} ^{−} \left(a q\right) + \text{NO}_{2} ^{−} \left(a q\right) \rightarrow \text{MnO}_{2} \left(s\right) + \text{NO}_{3} ^{−} \left(a q\right) (\text{in base})$

(b) $\text{MnO}_{4} ^{2−} \left(a q\right) \rightarrow \text{MnO}_{4} ^{−} \left(a q\right) + \text{MnO}_{2} \left(s\right) (\text{in base})$

(c) $\text{Br}_{2} \left(l\right) + \text{SO}_{2} \left(g\right) \rightarrow \text{Br}^{−} \left(a q\right) + \text{SO}_{4} ^{2−} \left(a q\right) (\text{in acid})$