The pH of a sample of hydrochloric acid is 3.5. What will be its pH when this solution is diluted?

Options

A. Less than 3.5
B. Equal to 3.5
C. More than 3.5
D. Exactly 3

Answer

To solve the problem of determining the pH of a diluted hydrochloric acid (HCl) solution, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding pH**: The pH scale ranges from 0 to 14. A pH of 7 is neutral, below 7 indicates acidity, and above 7 indicates basicity. In this case, a pH of 3.5 indicates that the solution is acidic.

2. **Effect of Dilution**: When an acid is diluted with water, the concentration of hydrogen ions (H⁺) in the solution decreases. This is because the same amount of acid is now spread out in a larger volume of solution.

3. **Relationship Between pH and Concentration**: The pH is calculated using the formula:
\[ \text{pH} = -\log[\text{H}^+] \]
where \([\text{H}^+]\) is the concentration of hydrogen ions. As the concentration of H⁺ ions decreases due to dilution, the pH value will increase.

4. **Conclusion**: Since the original pH of the hydrochloric acid solution is 3.5, when this solution is diluted, the pH will increase. Therefore, the new pH will be greater than 3.5.

5. **Final Answer**: The pH of the diluted hydrochloric acid will be greater than 3.5.