What is the pH of a solution prepared by dissolving 0.045 mol of a strong monoprotic acid HA in enough water to make 900.0 mL of solution? Assume complete dissociation.
Show the answer and explanation
Correct answer
A. 1.30
Principle or equation
For a strong monoprotic acid that fully dissociates, the concentration of H+ equals the acid concentration. pH = -log10[H+].
Why this answer is correct
Molarity of HA = 0.045 mol / 0.900 L = 0.050 M. Since it is monoprotic and strong, [H+] = 0.050 M. pH = -log(0.050) = 1.30.
Example
If 0.020 mol of strong monoprotic acid is in 500 mL, [H+] = 0.040 M, pH = 1.40.
This published item includes a stored explanation and passed the platform’s publication workflow. It is independent preparation material, not a claim of an official or recalled examination question.