The aqueous solution of which of the following salt will have the lowest pH ?

Options

A. `NaClO_(3)`
B. `NaClO`
C. `NaClO_(4)`
D. `NaClO_(2)`

Explanation

To determine which aqueous solution of the given salts will have the lowest pH, we need to analyze the hydrolysis of each salt and the strength of the acids produced.

### Step-by-Step Solution:

1. **Identify the Salts**: The salts given in the question are:
- NHClO3 (Ammonium chlorate)
- NHClO (Ammonium hypochlorite)
- NaClO4 (Sodium perchlorate)
- NaClO2 (Sodium chlorite)

2. **Understand Hydrolysis**: When these salts dissolve in water, they can undergo hydrolysis, which involves the reaction of the salt with water to produce an acid and a base. The strength of the resulting acid will influence the pH of the solution.

3. **Analyze Each Salt**:
- **NHClO3**: Hydrolyzes to produce HClO3 (chloric acid), which is a strong acid.
- **NHClO**: Hydrolyzes to produce HClO (hypochlorous acid), which is a weak acid.
- **NaClO4**: Hydrolyzes to produce HClO4 (perchloric acid), which is a very strong acid.
- **NaClO2**: Hydrolyzes to produce HClO2 (chlorous acid), which is a weak acid.

4. **Compare Acid Strengths**: The strength of the acids produced from the salts is crucial:
- HClO4 (from NaClO4) is the strongest acid among the acids produced.
- HClO3 (from NHClO3) is also strong but not as strong as HClO4.
- HClO (from NHClO) and HClO2 (from NaClO2) are weaker acids.

5. **Determine pH**: The pH of a solution is inversely related to the concentration of hydrogen ions (H⁺) in the solution. The stronger the acid, the more H⁺ ions it will produce, leading to a lower pH.

6. **Conclusion**: Since NaClO4 produces HClO4, which is the strongest acid, it will produce the highest concentration of H⁺ ions, resulting in the lowest pH.

### Final Answer:
The aqueous solution of **NaClO4** will have the lowest pH.

---