Among the following pairs, the one representing a conjugate pair of an acid & a base is

Options

A. `H_(3)O^(+)` & `H_(2)O`
B. `CH_(3)COOH` & `CH_(3)COONa`
C. `NH_(4)OH` & `NH_(4)CI`
D. `SO_(4)^(2-)` & `HSO_(4)^(-)`

Answer

To determine which of the given pairs represents a conjugate pair of an acid and a base, we need to understand the concept of conjugate acids and bases. According to the Brønsted-Lowry theory:

1. A **conjugate acid** is formed when a base gains a proton (H⁺).
2. A **conjugate base** is formed when an acid loses a proton (H⁺).

Now, let's analyze the given pairs:

### Given Pairs:
1. **H₃O⁺ and H₂O**
2. **CH₃CWH and CH₃CWNA**
3. **NH₄OH and NH₄Cl**
4. **SO₄²⁻ and HSO₄⁻**

### Step-by-Step Analysis:

**Step 1: Analyze the first pair (H₃O⁺ and H₂O)**
- H₂O can act as a base and accept a proton to form H₃O⁺.
- H₃O⁺ is the conjugate acid of H₂O.
- Therefore, H₃O⁺ and H₂O form a conjugate acid-base pair.

**Step 2: Analyze the second pair (CH₃CWH and CH₃CWNA)**
- Without specific details about the compounds, we cannot definitively identify them as a conjugate acid-base pair.
- However, based on the naming conventions, CH₃CWH is likely an acid and CH₃CWNA is likely a base, but they do not form a clear conjugate pair.

**Step 3: Analyze the third pair (NH₄OH and NH₄Cl)**
- NH₄OH (ammonium hydroxide) can act as a base, while NH₄Cl (ammonium chloride) is a salt.
- There is no direct proton transfer between these two, hence they do not form a conjugate acid-base pair.

**Step 4: Analyze the fourth pair (SO₄²⁻ and HSO₄⁻)**
- HSO₄⁻ can donate a proton to form SO₄²⁻.
- Therefore, SO₄²⁻ is the conjugate base of HSO₄⁻.
- This pair also represents a conjugate acid-base pair.

### Conclusion:
The pairs that represent conjugate acid-base pairs are:
- **H₃O⁺ and H₂O**
- **HSO₄⁻ and SO₄²⁻**

### Final Answer:
The pairs representing conjugate pairs of an acid & a base are **H₃O⁺ and H₂O**, and **HSO₄⁻ and SO₄²⁻**.