`NH_(4)^(+)` ion in an aqueous solution will behave as :

Options

A. A base
B. An acid
C. Both acid and base
D. Neutral

Explanation

To determine how the ammonium ion \((NH_4^+)\) behaves in an aqueous solution, we can analyze it step by step using the Bronsted-Lowry acid-base theory.

### Step-by-Step Solution:

1. **Understanding the Ammonium Ion**:
- The ammonium ion \((NH_4^+)\) is a positively charged ion formed when ammonia \((NH_3)\) accepts a proton \((H^+)\).

2. **Bronsted-Lowry Acid-Base Theory**:
- According to the Bronsted-Lowry theory, an acid is defined as a proton donor, while a base is a proton acceptor.
- In an aqueous solution, we need to consider how \((NH_4^+)\) interacts with water.

3. **Dissociation in Water**:
- When \((NH_4^+)\) is dissolved in water, it can donate a proton to water:
\[ NH_4^+ + H_2O \rightarrow NH_3 + H_3O^+ \]
- In this reaction, \((NH_4^+)\) donates a proton \((H^+)\) to water, forming hydronium ions \((H_3O^+)\) and ammonia \((NH_3)\).

4. **Behavior as an Acid**:
- Since \((NH_4^+)\) donates a proton, it behaves as an acid according to the Bronsted-Lowry definition.

5. **Weak Base Formation**:
- The reaction also produces ammonia, which can act as a weak base. However, the primary behavior of \((NH_4^+)\) in this context is as an acid.

6. **Conclusion**:
- Therefore, in an aqueous solution, the ammonium ion \((NH_4^+)\) behaves as an acid.

### Final Answer:
The ammonium ion \((NH_4^+)\) in an aqueous solution behaves as an **acid**.

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