The solution of which one of the following will have pH less than 7?

Options

A. NaOH
B. KCI
C. `FeCI_(3)`
D. NaCI

Explanation

To determine which solution has a pH less than 7, we need to identify the nature of the solutions provided in the options. A solution with a pH less than 7 is considered acidic. Let's analyze each option step by step.

### Step-by-Step Solution:

1. **Identify the Options**:
We need to evaluate the following options:
- A) NaOH
- B) KCl
- C) FeCl3
- D) NaCl

2. **Analyze NaOH**:
- NaOH is a strong base.
- The pH of a strong base is greater than 7 (typically around 14).
- **Conclusion**: NaOH does not have a pH less than 7.

3. **Analyze KCl**:
- KCl is a salt formed from a strong acid (HCl) and a strong base (KOH).
- The pH of a solution of KCl is neutral, which is 7.
- **Conclusion**: KCl does not have a pH less than 7.

4. **Analyze FeCl3**:
- FeCl3 is a salt formed from a weak base (Fe(OH)3) and a strong acid (HCl).
- The pH of a solution of FeCl3 is less than 7 because it is an acidic salt.
- **Conclusion**: FeCl3 has a pH less than 7.

5. **Analyze NaCl**:
- NaCl is a salt formed from a strong acid (HCl) and a strong base (NaOH).
- The pH of a solution of NaCl is neutral, which is 7.
- **Conclusion**: NaCl does not have a pH less than 7.

6. **Final Conclusion**:
- Among the options analyzed, only FeCl3 has a pH less than 7.
- Therefore, the correct answer is **C) FeCl3**.