Complete and balance the following reactions:
(i). `Mn^(2+)+PbO_2toMnO_4^(ɵ)+H_2O`
(ii). `Ag^(o+)+AsH_3toH_3AsO_3+H^(o+)`

Explanation

To complete and balance the given reactions, we will follow a systematic approach.

### Reaction (i):
**Given:**
\[ \text{Mn}^{2+} + \text{PbO}_2 \rightarrow \text{MnO}_4^{-} + \text{H}_2\text{O} \]

**Step 1: Identify oxidation states.**
- Manganese in \(\text{Mn}^{2+}\) has an oxidation state of +2.
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