What is the pH of a 0.0235 M HCl solution?
The correct answer and explanation is :
To calculate the pH of a 0.0235 M HCl solution, we use the formula:
[
\text{pH} = -\log [\text{H}^+]
]
Since HCl is a strong acid, it fully dissociates in water:
[
\text{HCl} \rightarrow \text{H}^+ + \text{Cl}^-
]
Thus, the concentration of hydrogen ions ((\text{H}^+)) is equal to the concentration of HCl:
[
[\text{H}^+] = 0.0235 \text{ M}
]
Now, calculating the pH:
[
\text{pH} = -\log (0.0235)
]
[
\text{pH} \approx 1.63
]
Explanation:
- Definition of pH: pH is a measure of the acidity of a solution, defined as the negative logarithm of the hydrogen ion concentration. Lower pH values indicate stronger acidity.
- HCl as a Strong Acid: Hydrochloric acid (HCl) is a strong acid, meaning it completely dissociates in water. This simplifies the calculation because the concentration of hydrogen ions is directly equal to the initial concentration of HCl.
- Logarithmic Calculation: The logarithm function helps convert hydrogen ion concentration into a more manageable scale (0 to 14). In this case, taking the negative logarithm of 0.0235 gives us a pH of approximately 1.63.
- Understanding the Result: Since the pH is less than 7, the solution is acidic. A pH of around 1.63 indicates a moderately strong acidic solution, which is expected for dilute strong acids like this one.
