Which of the following represents the isopolyacid of phosphorus ?

Options

A. `{:(" "O" "O),(" "||" "||),(H-P-O-P-O-H),(" "|" "|),(" "O-H" "O-H):}`
B. `H - overset(O) overset(||) underset(OH) underset(|)P - overset(O) overset(||)P -underset(OH) underset(|) OH`
C. `H-overset(O) overset(||) underset(OH) underset(|)P - O - overset(O) overset(||) underset(H) underset(|)P - H`
D. `HO - overset(O) overset(||) underset(OH) underset(|) P -O- overset(O) overset(||) underset(OH) underset(|)P - OH`

Answer

To determine which of the following represents the isopolyacid of phosphorus, we need to understand what an isopolyacid is and identify the correct molecular formula and structure.

### Step-by-Step Solution:

1. **Understanding Isopolyacids**:
- Isopolyacids are a type of polyacid that contains only one type of central atom (in this case, phosphorus) and are formed by the condensation of oxoacids of that element. They typically have the general formula \( H_nE_mO_k \), where \( E \) is the central atom.

2. **Identifying Phosphorus Isopolyacids**:
- The most common isopolyacids of phosphorus include phosphoric acid (\( H_3PO_4 \)), pyrophosphoric acid (\( H_4P_2O_7 \)), and metaphosphoric acid (\( HPO_3 \)). Among these, pyrophosphoric acid is a well-known isopolyacid.

3. **Analyzing Pyrophosphoric Acid**:
- Pyrophosphoric acid has the molecular formula \( H_4P_2O_7 \). In its structure, each phosphorus atom is tetrahedrally coordinated and forms one double bond with oxygen, two single bonds with hydroxyl groups, and a P-O-P linkage connecting the two phosphorus atoms.

4. **Conclusion**:
- Based on the structure and properties discussed, pyrophosphoric acid is indeed the isopolyacid of phosphorus. Therefore, the correct answer to the question is the option that represents pyrophosphoric acid, which is option number four.

### Final Answer:
The isopolyacid of phosphorus is represented by pyrophosphoric acid, with the molecular formula \( H_4P_2O_7 \).

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