Chose the correct acidity orders among the following.
(1) `H_(3)AsO_(4) < H_(3)PO_(4)`
(2) `H_(2)CO_(3) >H_(3)BO_(3)`
(3) `H_(3)AsO_(4)< H_(3)AsO_(2)`

Options

A. 1 and3
B. 1 and 2
C. 3 only
D. 2 and 3

Answer

To determine the correct acidity orders among the given compounds, we will analyze each statement one by one.

### Step 1: Analyze Statement (1) `H₃AsO₄ < H₃PO₄`

1. **Structure and Resonance**:
- Draw the structures of both acids.
- For `H₃AsO₄`, the conjugate base after losing an H⁺ would be `H₂AsO₄⁻`, which has resonance stabilization.
- For `H₃PO₄`, the conjugate base after losing an H⁺ would be `H₂PO₄⁻`, which also has resonance stabilization.

2. **Electronegativity**:
- Phosphorus (P) is more electronegative than Arsenic (As). This means that the negative charge in the conjugate base of `H₃PO₄` is more stabilized compared to that in `H₃AsO₄`.

3. **Conclusion**:
- Since the conjugate base of `H₃PO₄` is more stable due to higher electronegativity, `H₃PO₄` is more acidic than `H₃AsO₄`.
- Therefore, the order `H₃AsO₄ < H₃PO₄` is correct.

### Step 2: Analyze Statement (2) `H₂CO₃ > H₃BO₃`

1. **Structure and Resonance**:
- Draw the structures of both acids.
- For `H₂CO₃` (carbonic acid), the conjugate base after losing an H⁺ would be `HCO₃⁻`, which has resonance stabilization.
- For `H₃BO₃` (boric acid), the conjugate base after losing an H⁺ would be `H₂BO₃⁻`, which does not have significant resonance stabilization.

2. **Conclusion**:
- The conjugate base of `H₂CO₃` is more stable due to resonance, while `H₃BO₃` lacks such stabilization.
- Therefore, `H₂CO₃` is more acidic than `H₃BO₃`, making the order `H₂CO₃ > H₃BO₃` correct.

### Step 3: Analyze Statement (3) `H₃AsO₄ < H₃AsO₂`

1. **Structure and Resonance**:
- Draw the structures of both acids.
- For `H₃AsO₄`, the conjugate base after losing an H⁺ would be `H₂AsO₄⁻`, which has resonance stabilization.
- For `H₃AsO₂`, the conjugate base after losing an H⁺ would be `H₂AsO₂⁻`, which also has resonance stabilization but has fewer oxygen atoms to stabilize the negative charge.

2. **Conclusion**:
- `H₃AsO₄` is more acidic than `H₃AsO₂` because it has more oxygen atoms that can stabilize the negative charge in the conjugate base.
- Therefore, the order `H₃AsO₄ < H₃AsO₂` is incorrect.

### Final Conclusion

- The correct acidity orders are:
- (1) `H₃AsO₄ < H₃PO₄` is **correct**.
- (2) `H₂CO₃ > H₃BO₃` is **correct**.
- (3) `H₃AsO₄ < H₃AsO₂` is **incorrect**.

Thus, the correct options are (1) and (2) only.