The pH of a solution which is three times as acidic as pure water is

Options

A. 6.7
B. 3.5
C. `7.0`
D. 6.523

Answer

To find the pH of a solution that is three times as acidic as pure water, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the pH of Pure Water**:
- The pH of pure water is 7. This means that the concentration of hydrogen ions \([H^+]\) in pure water is \(10^{-7} \, \text{M}\).

2. **Determine the Concentration of the New Solution**:
- If the new solution is three times as acidic as pure water, then its hydrogen ion concentration will be three times that of pure water.
- Therefore, the concentration of hydrogen ions in the new solution \([H^+]_{new}\) can be calculated as:
\[ [H^+]_{new} = 3 \times [H^+]_{pure \, water} = 3 \times 10^{-7} \, \text{M} = 3 \times 10^{-7} \, \text{M} \]

3. **Calculate the pH of the New Solution**:
- The pH is calculated using the formula:
\[ pH = -\log[H^+] \]
- Substitute the new concentration into the formula:
\[ pH = -\log(3 \times 10^{-7}) \]
- Using the logarithmic property \(\log(ab) = \log a + \log b\):
\[ pH = -(\log 3 + \log(10^{-7})) \]
- We know that \(\log(10^{-7}) = -7\), so:
\[ pH = -\log 3 + 7 \]

4. **Find the Value of \(\log 3\)**:
- The value of \(\log 3\) is approximately \(0.4771\).
- Substitute this value into the pH equation:
\[ pH = -0.4771 + 7 = 6.5229 \]

5. **Final Result**:
- The pH of the solution which is three times as acidic as pure water is approximately \(6.523\).

### Final Answer:
The pH of the solution is **6.523**.