A solution is prepared by dissolving 0.0150 mol of a strong monoprotic acid HA in enough water to make 300.0 mL of solution. What is the pH of the resulting solution? Assume complete dissociation.
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Correct answer
A. 1.30
Principle or equation
For a strong monoprotic acid, [H+] equals the initial acid concentration. pH = -log10[H+]. Molarity = moles/volume in liters.
Why this answer is correct
Moles of HA = 0.0150 mol, volume = 0.300 L, so [H+] = 0.0150 / 0.300 = 0.0500 M. pH = -log(0.0500) = 1.301, which rounds to 1.30.
Example
If 0.010 mol of HCl is dissolved in 0.500 L, [H+] = 0.020 M, pH = 1.70.
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