17.4 – 17.5 Student Notes

V. Acid-Base Properties of Salt Solutions

A. Hydrolysis –

B. Prediction of Whether a Salt Solution is Acidic, Basic, or Neutral

1. A salt of a strong base and a strong acid.

2. A salt of a strong base and a weak acid.

3. A salt of a weak base and a strong acid.

4. A salt of a weak acid and a weak base.

C. Predicting Whether a Salt Solution is Acidic, Basic, or Neutral

Decide whether aqueous solutions of the following salts are acidic, basic, or neutral:

a. KCl

b. NaF

c. Zn(NO₃)₂

d. NH₄CN

D. The pH of a Salt Solution

1. K_aK_b = K_w

2. Obtaining K_a from K_b or K_b from K_a

Use Tables 17.1 and 17.2 to obtain the following at 25° C:

a. K_b for CN^-

b. K_a for NH₄⁺

3. Calculating Concentrations of Species in a Salt Solution

What is the pH of 0.10 M sodium nicotinate at 25° C? The K_a for nicotinic acid was determined in Example 17.1 to be 1.4 x 10^-5 at 25° C.

4. Which of the following aqueous solutions has the highest pH and which has the lowest:

a. 0.1 M NH₃

b. 0.1 M NH₄Br

c. 0.1 M NaF

d. 0.1 M NaCl

VI. Solutions of a Weak Acid or Base with Another Solute

A. Common Ion Effect

1. Def –

2. Calculating the Common-Ion Effect on Acid Ionization (Effect of a Strong Acid)

The degree of ionization of acetic acid, HC₂H₃O₂, in a 0.10 M aqueous solution at 25° C is 0.013. K_a at this temperature is 1.7 x 10^-5. Calculate the degree of ionization of HC₂H₃O₂ in a 0.10 M solution at ° C to which sufficient HCl is added to make it 0.010 M HCl. How is the degree of ionization affected?

3. Calculating the Common-Ion Effect on Acid Ionization (Effect of a Conjugate Base)

A solution is prepared to be 0.10 M acetic acid, HC₂H₃O₂, and 0.20 M sodium acetate, NaC₂H₃O₂. What is the pH of this solution at 25° C? K_a for acetic acid is 1.7 x 10^-5.