Ammonia gas dissolves in water to form `NH_(4)OH`. In this reaction water acts as

Options

A. An acid
B. A base
C. A salt
D. A conjugate base

Answer

To determine how water acts in the reaction where ammonia gas dissolves in water to form NH₄OH, we can analyze the reaction step by step.

### Step 1: Write the Reaction
When ammonia (NH₃) dissolves in water (H₂O), it forms ammonium hydroxide (NH₄OH). The reaction can be represented as:
\[ \text{NH}_3(g) + \text{H}_2\text{O}(l) \rightleftharpoons \text{NH}_4^+(aq) + \text{OH}^-(aq) \]

### Step 2: Identify the Species Involved
In this reaction:
- NH₃ is the ammonia gas.
- H₂O is water.
- NH₄⁺ is the ammonium ion.
- OH⁻ is the hydroxide ion.

### Step 3: Analyze the Role of Water
In the reaction, water (H₂O) donates a proton (H⁺) to ammonia (NH₃). This donation of a proton leads to the formation of the ammonium ion (NH₄⁺) and the hydroxide ion (OH⁻).

### Step 4: Classify the Role of Water
Since water donates a proton (H⁺) to ammonia, it acts as an acid in this reaction. According to the Brønsted-Lowry theory of acids and bases, an acid is defined as a substance that donates protons.

### Conclusion
Thus, in the reaction where ammonia gas dissolves in water to form NH₄OH, water acts as an acid.

### Final Answer
Water acts as an acid in this reaction.

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