Give the structural formula for the following :
(i) Phosphorous acid, `H_3 PO_3`
(ii) Pyrophosphoric acid, `H_4 P_2 O_7`.

Explanation

To provide the structural formulas for the given compounds, we will follow a systematic approach for each acid.

### (i) Phosphorous Acid, `H₃PO₃`

1. **Identify the central atom**: The central atom in phosphorous acid is phosphorus (P).
2. **Count the total number of oxygen atoms**: There are 3 oxygen atoms in `H₃PO₃`.
3. **Determine the bonding**: Phosphorous acid is an oxa-acid, which means it contains P=O (double bond) and P-OH (single bond) groups.
4. **Construct the structure**:
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