Complete the following reactions
(a)`CO+H_(2)underset("420-670k,300atm")overset("ZnO+Cu")to`.....
(b)`R_(3)SiOH+OHSiR_(3)to`....+....
( c)`Na_(2)CO_(3)+Sito`...+....

Explanation

Let's complete the reactions step by step.

### Reaction (a):
**Given:**
\[ \text{CO} + \text{H}_2 \underset{420-670 \text{ K}, 300 \text{ atm}}{\overset{\text{ZnO} + \text{Cu}}{\rightarrow}} \]

**Step 1:** Identify the reactants and conditions.
- Reactants: Carbon monoxide (CO) and hydrogen gas (H2).
...