Question

What is the pH of a 0.01 M solution of hydrochloric acid (HCl)?

• A. \( 1 \)
• B. \( 2 \)
• C. \( 3 \)
• D. \( 4 \)

Hint:

For strong acids, the pH is calculated directly from the concentration of the acid since they dissociate completely. Use the formula \( \text{pH} = -\log [\text{H}^+] \).

Answer 1

The Correct Option is B

Step 1: Characterize the acid. Hydrochloric acid (HCl) is classified as a strong acid. This indicates that it undergoes complete dissociation in aqueous solution: \[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \] Step 2: Determine the hydrogen ion concentration. Due to the complete dissociation of HCl, the molar concentration of hydrogen ions \( [\text{H}^+] \) is equivalent to the initial molar concentration of the acid: \[ [\text{H}^+] = 0.01 \, \text{M} \] Step 3: Apply the pH definition. The pH of a solution is mathematically defined as: \[ \text{pH} = -\log [\text{H}^+] \] By substituting the calculated hydrogen ion concentration: \[ \text{pH} = -\log (0.01) = 2 \] Answer: The resultant pH of the solution is 2.