Whether a negative value of pH is possible

Options

A. Yes
B. No
C. Some times
D. None of these

Answer

To determine whether a negative value of pH is possible, we need to understand the concept of pH and its range.

### Step-by-Step Solution:

1. **Definition of pH**:
pH is a measure of the hydrogen ion concentration \([H^+]\) in a solution. It is defined by the formula:
\[ \text{pH} = -\log[H^+] \]
This means that pH is the negative logarithm of the hydrogen ion concentration.

2. **Understanding the pH Scale**:
The pH scale typically ranges from 0 to 14 at 25°C:
- A pH of 7 is considered neutral (pure water).
- A pH less than 7 indicates an acidic solution.
- A pH greater than 7 indicates a basic (alkaline) solution.

3. **Hydrogen Ion Concentration**:
The concentration of hydrogen ions \([H^+]\) in a solution can vary widely. For example:
- A neutral solution has \([H^+]\) of \(1 \times 10^{-7} \, \text{M}\), which gives a pH of 7.
- Strong acids can have much higher concentrations of \([H^+]\), leading to lower pH values.

4. **Calculating pH Values**:
If we consider very strong acids, the concentration of hydrogen ions can exceed \(1 \, \text{M}\). For example, if \([H^+]\) is \(10 \, \text{M}\):
\[ \text{pH} = -\log(10) = -1 \]
This calculation shows that theoretically, a negative pH value can be calculated.

5. **Practical Considerations**:
While the calculation suggests that negative pH values can exist, in practice, the pH scale is defined from 0 to 14 for most common solutions at 25°C. Extreme conditions (like very concentrated acids) may lead to negative pH values, but these are not typically encountered in standard chemistry contexts.

6. **Conclusion**:
Although mathematically possible under certain conditions, negative pH values are not commonly observed in typical aqueous solutions. Therefore, while it is theoretically possible to have a negative pH, it is not practical or relevant in most chemical contexts.

### Final Answer:
No, a negative value of pH is not possible in standard conditions, but theoretically, it can occur under extreme concentrations of hydrogen ions.