Which is incorrect ?

Options

A. Conjugate acid of `H_2O "is" H_3O^+`
B. Conjugate base of `HCO_3-"is" CO_3^(2-)`
C. Conjugate base of `NH_3 "is " NH_2^(Theta)`
D. Conjugate base of HOCI is `CI^-`

Answer

To solve the question "Which is incorrect?" regarding conjugate acids and bases, we will analyze each statement provided in the question step by step.

### Step 1: Understand Conjugate Acids and Bases
- **Conjugate Acid**: A species formed when a base accepts a proton (H⁺).
- **Conjugate Base**: A species formed when an acid donates a proton (H⁺).

### Step 2: Analyze Each Statement

1. **Statement 1**: "Conjugate acid of H₂O is H₃O⁺"
- When water (H₂O) acts as a base and accepts a proton (H⁺), it forms hydronium ion (H₃O⁺).
- **Conclusion**: This statement is correct.

2. **Statement 2**: "Conjugate base of HCO₃⁻ is CO₃²⁻"
- The bicarbonate ion (HCO₃⁻) can donate a proton (H⁺) to form carbonate ion (CO₃²⁻).
- **Conclusion**: This statement is correct.

3. **Statement 3**: "Conjugate base of NH₃ is NH₂⁻"
- Ammonia (NH₃) can donate a proton (H⁺) to form the amide ion (NH₂⁻).
- **Conclusion**: This statement is correct.

4. **Statement 4**: "Conjugate base of HOCl is Cl⁻"
- Hypochlorous acid (HOCl) can donate a proton (H⁺) to form hypochlorite ion (OCl⁻), not chloride ion (Cl⁻).
- **Conclusion**: This statement is incorrect.

### Final Conclusion
- The incorrect statement is: "Conjugate base of HOCl is Cl⁻".