In the titration of `NH_(4)OH` versus `HCl`, the `pH` of the solution at equivalence point is about:

Options

A. `5.5`
B. `7`
C. `8.5`
D. `9.5`

Explanation

To determine the pH at the equivalence point in the titration of ammonium hydroxide (NH4OH) with hydrochloric acid (HCl), we can follow these steps:

### Step 1: Identify the nature of the reactants
- Ammonium hydroxide (NH4OH) is a weak base.
- Hydrochloric acid (HCl) is a strong acid.

### Step 2: Write the neutralization reaction
- The reaction between NH4OH and HCl can be represented as:
\[ \text{NH}_4\text{OH} + \text{HCl} \rightarrow \text{NH}_4\text{Cl} + \text{H}_2\text{O} \]
- This reaction produces ammonium chloride (NH4Cl), which is a salt.

### Step 3: Analyze the salt formed
- Ammonium chloride (NH4Cl) is a salt formed from a weak base (NH4OH) and a strong acid (HCl).
- The nature of the solution at the equivalence point is determined by the properties of this salt.

### Step 4: Determine the pH at the equivalence point
- Since NH4Cl is a salt of a weak base and a strong acid, it will hydrolyze in water to produce an acidic solution:
\[ \text{NH}_4^+ + \text{H}_2\text{O} \rightleftharpoons \text{NH}_4\text{OH} + \text{H}^+ \]
- This reaction shows that NH4+ ions will release H+ ions into the solution, making the solution acidic.

### Step 5: Conclusion about pH
- Therefore, at the equivalence point, the pH of the solution will be less than 7, indicating an acidic solution.
- Among the given options (5.5, 7, 8.5, and 9.5), the only value that is less than 7 is 5.5.

### Final Answer
- The pH of the solution at the equivalence point is approximately **5.5**.

---