Which statements is wrong about pH ?

Options

A. pH of pure water is not zero
B. Adding 1 N solution `CH_3COOH and 1 N` NaOH pH will be seven
C. pH of dilute and hot `H_2SO_4` is less then 7
D. Mixing solution of `CH_3COOH and HCI` pH will be less than 7

Answer

To determine which statement about pH is incorrect, we need to analyze the provided statements one by one.

### Step-by-Step Solution:

1. **Understanding pH of Pure Water**:
- The first statement claims that the pH of pure water is not zero. This is true. The pH of pure water at 25 degrees Celsius is 7, which indicates neutrality. A pH of 0 would indicate a very acidic solution, which is not the case for pure water.

2. **pH of Pure Water**:
- The statement that "both H⁺ and OH⁻ are the same in pure water" is also true. In pure water, the concentration of hydrogen ions [H⁺] is equal to the concentration of hydroxide ions [OH⁻], both being 1 x 10⁻⁷ M at 25 degrees Celsius.

3. **pH of Solutions**:
- The statement that "at 25 degrees Celsius, pH is 7" is correct. This is a standard reference point for pure water.

4. **Neutralization Reaction**:
- The next part discusses adding a 1N solution of acetic acid (CH₃COOH) and a 1N solution of sodium hydroxide (NaOH). The resulting solution will form sodium acetate (CH₃COONa) and water. Sodium acetate is a salt derived from a weak acid and a strong base, which typically results in a solution with a pH greater than 7 due to hydrolysis.

5. **Hydrolysis of Sodium Acetate**:
- The hydrolysis of CH₃COO⁻ ions will produce CH₃COOH and OH⁻, leading to a pH greater than 7. This statement is correct.

6. **pH of Dilute H₂SO₄**:
- The statement regarding dilute sulfuric acid (H₂SO₄) having a pH less than 7 is also correct, as H₂SO₄ is a strong acid.

7. **Mixing Acetic Acid and HCl**:
- The final statement about mixing acetic acid (CH₃COOH) and hydrochloric acid (HCl) resulting in a pH less than 7 is correct, as both are acids and will increase the concentration of H⁺ ions.

### Conclusion:
The only incorrect statement is that "the pH of pure water is zero." The correct pH of pure water at 25 degrees Celsius is 7.