Question

Calculate the pH of a \(0.01\,M\) \(HCl\) solution.

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

For strong acids, assume complete dissociation. Thus, the hydrogen ion concentration equals the molarity of the acid.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
We are given the molar concentration of a hydrochloric acid (\(HCl\)) solution and need to calculate its pH level.
Step 2: Key Formula or Approach:
The pH of an aqueous solution is defined as the negative base-10 logarithm of the hydrogen ion concentration:
\[ pH = -\log_{10}[H^+] \] Because \(HCl\) is a strong acid, it dissociates completely into \(H^+\) and \(Cl^-\) ions in water.
Step 3: Detailed Solution:
Since \(HCl\) is a strong, monoprotic acid, its complete dissociation means the concentration of hydrogen ions is equal to the initial concentration of the acid:
\[ [H^+] = 0.01\,M \] Express this concentration in scientific notation for easier calculation:
\[ [H^+] = 10^{-2}\,M \] Apply the pH formula:
\[ pH = -\log(10^{-2}) \] Using the logarithm power rule (\(\log(a^b) = b \cdot \log a\)):
\[ pH = -(-2)\log(10) \] Since \(\log(10) = 1\):
\[ pH = 2 \] Step 4: Final Answer:
The pH of the \(0.01\,M\) \(HCl\) solution is \(2\).