Which among the following statement is/are correct ?

Options

A. `pH=-log_(10)[H_(3)O^(+)]` for dilute solution
B. pH of `H_(2)O` decreases with increase of temperature
C. pH can not more than 14
D. If a solution is diluted ten times, its pH always increases by 1

Answer

To determine which of the given statements is/are correct, let's analyze each statement one by one.

### Step 1: Analyze Statement 1
**Statement:** pH is minus log base 10 hydronium ion concentration for dilute solution.

**Analysis:**
The definition of pH is pH = -log[H⁺] or pH = -log[H₃O⁺]. This definition holds true for all solutions, not just dilute ones. Therefore, the statement is incorrect.

### Step 2: Analyze Statement 2
**Statement:** pH of water decreases with increase of temperature.

**Analysis:**
As temperature increases, the dissociation constant (Kₐ) of water increases, leading to an increase in the concentration of H⁺ ions. Since pH is calculated as pH = -log[H⁺], an increase in [H⁺] results in a decrease in pH. Therefore, this statement is correct.

### Step 3: Analyze Statement 3
**Statement:** pH cannot be more than 14.

**Analysis:**
The pH scale typically ranges from 0 to 14, but this is not a strict limit. For very strong bases, the pH can exceed 14. Therefore, this statement is incorrect.

### Step 4: Analyze Statement 4
**Statement:** If a solution is diluted 10 times, its pH always increases by 1.

**Analysis:**
When a solution is diluted 10 times, the concentration of H⁺ ions decreases by a factor of 10. If the initial concentration is C, after dilution, the new concentration becomes C/10. The pH change can be calculated as follows:
- Initial pH = -log[C]
- New pH = -log[C/10] = -log[C] - log[0.1] = -log[C] + 1
Thus, the pH increases by 1 when diluted 10 times. Therefore, this statement is correct.

### Conclusion
The correct statements are:
- Statement 2: pH of water decreases with increase of temperature (Correct)
- Statement 4: If a solution is diluted 10 times, its pH always increases by 1 (Correct)

### Final Answer
The correct statements are **Statement 2 and Statement 4**.

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