Review – Part II
a. The Ka expression for acids and calculations involving Ka.
1. Caprytic acid, also called octanoic acid, is an 8-carbon fatty acid that is used as a sanitizer on dairy
equipment that comes in contact with milk. The acid has a molar mass of 144.21 g/mol. An aqueous
solution of the sanitizer containing 12.25 g/L has a pH of 2.98. What is the acid-dissociation constant, Ka,
for caprytic acid?
b. Percent dissociation calculations
2. Citric acid, C6H8O7(aq) is used to add a sour taste to foods and soft drinks. It is prepared in a solution
with a concentration of 0.52 mol/L, and has a pH of 1.72. Calculate the acid-dissociation constant for
citric acid. What percentage of citric acid molecules ionizes in the solution?
C. Equilibrium position and strength of acids and bases
3. Sodium hydrogen sulfite, NaHSO3(s) is dissolved in water (hint: the sodium hydrogen sulfite
dissociates completely into sodium ions and hydrogen sulfite ions.) What happens to the hydrogen
sulfite ion in water?
d. The Kb expression for bases and calculations involving Kb.
4. Determine the pH of a 0.25 mol/L ammonia solution prepared by Mr. Dvorsky. For this base, Kb = 1.8
x 10-5.
e. The relationship of Ka, Kb, and Kw
5. Calculate the Ka for the conjugate acid of C2H5NH3(aq) (Kb = 4.5 x 10-4).
f. Titration of strong acid and strong base
6. At the equivalence point, 18.76 ml of 1.75 mol/L potassium hydroxide, KOH(aq) has been titrated with
28.65 ml of hydrochloric acid. What is the concentration of the original hydrochloric acid solution?
7. What volume of a 0.22 mol/L hydrochloric acid solution, HCl(aq) is needed to cause the pH of 25.00
ml of a 0.15 mol/L lithium hydroxide solution, LiOH(aq) to have a pH that is equal to 7.00?
g. buffers and buffer preparation