Which of the following species can be formed in acid-base reactions as Bronsted base as well as Bronsted acids?

Options

A. `[Fe(H_(2)O)_(5)]^(3+)`
B. `HPO_(4)^(-)`
C. `SO_(4)^(2)`
D. `NH_(4)^(+)`

Answer

To determine which species can act as both a Brønsted acid and a Brønsted base in acid-base reactions, we need to analyze each given species based on the definitions of Brønsted acids and bases:

1. **Brønsted Acid**: A substance that donates a proton (H⁺).
2. **Brønsted Base**: A substance that accepts a proton (H⁺).

Now, let's evaluate each option provided in the question:

### Step-by-Step Solution:

**Option 1: Fe(H₂O)₅³⁺**
- This species can donate a proton (acting as a Brønsted acid) but cannot accept a proton (cannot act as a Brønsted base).
- **Conclusion**: Brønsted acid only.

**Option 2: HBO₄⁻**
- This species can both donate a proton (acting as a Brønsted acid) and accept a proton (acting as a Brønsted base).
- **Conclusion**: Can act as both a Brønsted acid and a Brønsted base.

**Option 3: SO₄²⁻**
- This species can accept a proton (acting as a Brønsted base) but cannot donate a proton (cannot act as a Brønsted acid).
- **Conclusion**: Brønsted base only.

**Option 4: NH₄⁺**
- This species can donate a proton (acting as a Brønsted acid) but cannot accept a proton (cannot act as a Brønsted base).
- **Conclusion**: Brønsted acid only.

### Final Answer:
The only species that can act as both a Brønsted acid and a Brønsted base is **HBO₄⁻**.

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