Chem 1412 Chapter 17 Homework

CHAPTER 17- Homework Problems (Set.5)

Salts, Buffers, and Titration

Problem #1. A 0.20 M solution of a weak monoprotic acid is 0.22 % ionized. What is the acid-
ionization constant, Ka, for this acid?

Problem #2. A 0.010 M aqueous solution of a weak acid HA has a pH of 4.0. What is the degree
of ionization of HA in the solution?

Problem #3. What is the pH of a 0.35 M solution of methylamine (CH3NH2, Kb = 4.4 × 10–4)
at 25oC?

Problem #4. . What is the pH of a 0.24 M solution of sodium propionate, NaC3H5O2, at 25°C?
(For propionic acid, HC3H5O2, Ka = 1.3 × 10–5 at 25°C.)

Problem #5. (a) What is the pH of the solution if 8.90 g of sodium fluoride is added to
220.0 mL of a 0.770 M HF solution? Ka for HF is 6.8 × 10–4.
(b) What is the pH after the addition of 0.020 mole of HCl.

Problem #6. A mixture is made by adding 24.0 mL of 0.350 M KOH and 36.0 mL of 0.225 M
HNO3. After the reaction, what will be the pH of the resulting solution.

Problem #7. (a)How many milliliters of 0.0839 M NaOH are required to titrate 25.0 mL of
0.0990 M HF to the equivalence point?
(b) What would be the pH of the solution at the equivalence point.

Problem #8. A 25.0 mL sample of 0.150 M hydrazoic acid is titrated with a 0.250 M NaOH
solution. What is the pH after 10.0 mL of base is added?
The Ka of hydrazoic acid is 1.9 × 10-5.



Solubility

Problem #9. Write the correct solubility-product expression for the following equilibrium
reactions.

(a) PbI2 (s)  Pb2+(aq) + 2I−(aq)

(b) AgCl (s)  Ag+(aq) + Cl− (aq)

(c) La(IO3)3 (s)  La3+(aq) + 3IO3−(aq)

Problem #10.
(a) Calculate the solubility of La(IO3)3 in water in moles per liter (M) using its
Ksp value of 6.0x10-10.
(b) What concentration of La3+ is necessary to have a concentration
of 0.020 M IO3− ?