In the titration of NaOH and HCl, which of the following indicator will be used?

Options

A. Methyl orange
B. Methyl red
C. Both A and B
D. None of the above

Explanation

To determine the appropriate indicator for the titration of NaOH (a strong base) and HCl (a strong acid), we can follow these steps:

### Step 1: Identify the nature of the reactants
- NaOH is a strong base, while HCl is a strong acid. When titrating a strong acid with a strong base, the resulting solution at the equivalence point will have a neutral pH of 7.

**Hint:** Remember that strong acids and strong bases completely dissociate in solution.

### Step 2: Understand the equivalence point
- The equivalence point in a titration is where the amount of acid equals the amount of base, resulting in a neutral solution. For the titration of NaOH and HCl, this point occurs at pH 7.

**Hint:** The equivalence point is crucial for choosing the right indicator, as it tells you what pH to look for.

### Step 3: Choose the appropriate indicator
- An indicator is a substance that changes color at a specific pH range. For a titration that reaches a pH of 7, we need an indicator that changes color around this pH.

- Methyl orange is an indicator that changes color at a pH range of 3.1 to 4.4, which is too acidic for our titration.

- Phenolphthalein, on the other hand, changes color in the range of pH 8.2 to 10.0, which is slightly basic. However, it is more suitable than methyl orange for this titration.

**Hint:** Check the pH range of different indicators to see if they match the pH at the equivalence point.

### Step 4: Conclusion
- Given that the equivalence point for the titration of NaOH and HCl is at pH 7, the best choice of indicator would be phenolphthalein, as it indicates a transition from colorless to pink as the solution becomes slightly basic after the equivalence point.

**Final Answer:** The best indicator to use in the titration of NaOH and HCl is **Phenolphthalein**.