A student dissolves 0.010 mol of a strong monoprotic acid HA in enough water to make 250.0 mL of solution. What is the pH of the resulting solution? Assume complete dissociation.
Show the answer and explanation
Correct answer
A. 1.40
Principle or equation
For a strong monoprotic acid, the concentration of H+ equals the acid concentration. pH = -log10[H+]. Molarity = moles / volume in liters.
Why this answer is correct
First, calculate the molarity: 0.010 mol / 0.250 L = 0.040 M. Since the acid is strong and monoprotic, [H+] = 0.040 M. Then pH = -log10(0.040) = 1.40 (since log10(0.040) = -1.3979).
Example
If 0.020 mol of HCl is dissolved in 500 mL, molarity = 0.020/0.500 = 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.