Which of the following acids forms three series of salts?

Options

A. `H_(3)PO_(2)`
B. `H_(3)BO_(3)`
C. `H_(3)PO_(4)`
D. `H_(3)PO_(3)`

Explanation

To determine which of the given acids forms three series of salts, we need to analyze the number of ionizable hydrogens in each acid. The acids provided are H3PO2, H3BO3, H3PO4, and H3PO3.

### Step-by-Step Solution:

1. **Understanding Ionizable Hydrogens**:
- An acid can form salts based on the number of ionizable hydrogens it has. Each ionizable hydrogen can be replaced by a metal ion to form a salt. Therefore, an acid with three ionizable hydrogens can form three different series of salts.

2. **Analyzing H3PO2 (Phosphorous Acid)**:
- The structure of H3PO2 shows that it has only one ionizable hydrogen. Therefore, it can only form one series of salts.
- **Conclusion**: H3PO2 does not meet the criteria.

3. **Analyzing H3BO3 (Boric Acid)**:
- Boric acid (H3BO3) is a weak acid that does not lose protons in the traditional sense. Instead, it forms complexes with hydroxide ions (OH⁻). Hence, it does not have ionizable protons that can form salts.
- **Conclusion**: H3BO3 does not meet the criteria.

4. **Analyzing H3PO3 (Phosphorous Acid)**:
- H3PO3 has two ionizable hydrogens. It can form two series of salts.
- **Conclusion**: H3PO3 does not meet the criteria.

5. **Analyzing H3PO4 (Phosphoric Acid)**:
- H3PO4 has three ionizable hydrogens. It can lose these protons to form three different series of salts:
- First ionization: H3PO4 → H2PO4⁻ (Dihydrogen phosphate)
- Second ionization: H2PO4⁻ → HPO4²⁻ (Hydrogen phosphate)
- Third ionization: HPO4²⁻ → PO4³⁻ (Phosphate)
- Therefore, H3PO4 can form salts such as NaH2PO4, Na2HPO4, and Na3PO4.
- **Conclusion**: H3PO4 meets the criteria.

### Final Answer:
The acid that forms three series of salts is **H3PO4**.

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