Which of the following oxyacids of phosphorous are monoprotic
(mono basic) ? .

Options

A. `H_(3)PO_(3)`
B. `H_(3)PO_(4)`
C. `H_(3)PO_(2)`
D. `H_(4)P_(2)O_(7)`

Answer

To determine which oxyacids of phosphorus are monoprotic (monobasic), we need to analyze the structures of the given oxyacids and identify how many ionizable hydrogen atoms (H) are present. An ionizable hydrogen atom is typically found in a hydroxyl (–OH) group.

### Step-by-Step Solution:

1. **Identify the Oxyacids**: The oxyacids of phosphorus we need to analyze are H3PO3, H3PO4, H3PO2, and H4P2O7.

2. **Analyze H3PO3 (Phosphorous Acid)**:
- Structure: H3PO3 has three hydrogen atoms, with two of them in hydroxyl groups (–OH) and one bonded directly to phosphorus (P-H).
- Ionizable H: The two –OH groups can release H+ ions, indicating that H3PO3 is dibasic (not monoprotic).

3. **Analyze H3PO4 (Phosphoric Acid)**:
- Structure: H3PO4 has four hydrogen atoms, all of which are part of three hydroxyl groups (–OH).
- Ionizable H: Since there are three ionizable –OH groups, H3PO4 is tribasic (not monoprotic).

4. **Analyze H3PO2 (Hypophosphorous Acid)**:
- Structure: H3PO2 has two hydrogen atoms in hydroxyl groups and one hydrogen atom directly bonded to phosphorus.
- Ionizable H: There is only one ionizable –OH group, making H3PO2 monoprotic (monobasic).

5. **Analyze H4P2O7 (Pyrophosphoric Acid)**:
- Structure: H4P2O7 has four hydrogen atoms, with multiple –OH groups.
- Ionizable H: There are four –OH groups, indicating that H4P2O7 is tetrabasic (not monoprotic).

6. **Conclusion**: After analyzing all the oxyacids, the only monoprotic (monobasic) oxyacid of phosphorus is H3PO2.

### Final Answer:
The oxyacid of phosphorus that is monoprotic (monobasic) is **H3PO2**.