The best indicator for titrating HCl against `NH_(4)OH` is :

Options

A. Litmus
B. Phenolphthalein
C. Phenol red
D. Methyl orange

Explanation

To determine the best indicator for titrating HCl against NH₄OH, we need to analyze the nature of the acid and base involved in the titration, as well as the pH range of the indicators provided.

### Step-by-Step Solution:

1. **Identify the Acid and Base**:
- Hydrochloric acid (HCl) is a strong acid.
- Ammonium hydroxide (NH₄OH) is a weak base.

2. **Determine the Nature of the Salt Formed**:
- When HCl reacts with NH₄OH, they produce ammonium chloride (NH₄Cl) and water.
- NH₄Cl is an acidic salt because it is derived from a strong acid (HCl) and a weak base (NH₄OH).

3. **Understand the pH at Equivalence Point**:
- The pH at the equivalence point of a titration involving a strong acid and a weak base will be less than 7, indicating an acidic solution.

4. **Evaluate the Indicators**:
- **Litmus**: pH range 5 to 8 (changes color around neutral).
- **Phenolphthalein**: pH range 8.3 to 10 (changes color in basic range).
- **Phenol Red**: pH range 6.5 to 8.2 (changes color in slightly basic range).
- **Methyl Orange**: pH range 3.1 to 4.4 (changes color in acidic range).

5. **Select the Best Indicator**:
- Since the equivalence point is in the acidic range (due to the formation of NH₄Cl), we need an indicator that works well in this acidic range.
- Methyl orange, with a transition range of 3.1 to 4.4, is suitable because it will change color in the acidic pH range, allowing for a clear indication of the endpoint of the titration.

6. **Conclusion**:
- The best indicator for titrating HCl against NH₄OH is **Methyl Orange**.

### Final Answer:
The best indicator for titrating HCl against NH₄OH is **Methyl Orange**.