Weak Acids and Bases Practice Problems
1. The pKa of acetic acid is 4.75. Find the pH of acetic acid solutions of labeled
concentrations of 1.0 M, 0.010 M, and 0.00010 M.
2. Household vinegar is usually 5% acetic acid by volume. Calculate the molarity of this
solution. Assume density of solution to be 1 g/mL. The formula weight of CH3COOH is
60. What is the pH of household vinegar?
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3. Chlorous acid has a formula of HClO2. Its pKa is 1.92. What is the pH of a 0.75M
solution?
4. Given the pKa for ammonium ion is 9.26, what is the pH of 1.00 L of solution which
contains 5.45 g of NH4Cl (the molar mass of NH4Cl = 54.5 g mol¯1.)
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5. Find the pH of a 0.20 M solution of sodium propionate (C2H5COONa), where the Ka of
propionic acid = 1.34 x 10¯5.
6. Determine the Ka of the weak acid HX knowing that a 0.10 M solution of LiX has pH =
8.90
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7. A weak acid has a pKa of 4.994 and the solution pH is 4.523. What percentage of the acid
is dissociated?
8. Calculate the pH of a 0.100 M KCN solution. Ka(HCN) = 6.2 x 10 -10
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