Question 1

Which of the following best describes the common-ion effect?

Accepted Answer

The decrease in ionization of a weak acid or base when a strong electrolyte containing a common ion is added.

Question 2

A buffer solution is prepared by mixing 0.20 mol of acetic acid ($$\mathrm{CH_3COOH}) $$and 0.20 mol of sodium acetate ($$\mathrm{NaCH_3COO}) in $$enough water to make 1.0 L of solution. What will happen to the pH if a small amount of HCl is added?

Accepted Answer

The pH will decrease slightly.

Question 3

Which equation is the Henderson-Hasselbalch equation for a buffer made from a weak acid and its conjugate base?

Accepted Answer

$$\mathrm{pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right)}$$

Question 4

A buffer is most effective when:

Accepted Answer

The concentrations of weak acid and conjugate base are equal.

Question 5

What is the pH of a buffer solution that is 0.12 M in lactic acid ($$\mathrm{pK_a = 3.86}) $$and 0.10 M in sodium lactate?

Accepted Answer

$$\mathrm{pH = 3.86 + \log \left( \frac{0.10}{0.12} \right) = 3.80}$$

Question 6

Which of the following statements about buffer capacity is correct?

Accepted Answer

Buffer capacity increases as the total concentration of buffer components increases.

Question 7

A buffer is prepared by mixing 0.30 mol of acetic acid and 0.30 mol of sodium acetate in 1.00 L of water. If 0.020 mol of NaOH is added, what is the new pH? ($$\mathrm{pK_a = 4.74})$$

Accepted Answer

$$\mathrm{pH = 4.74 + \log \left( \frac{0.32}{0.28} \right) = 4.80}$$

Question 8

Which of the following best explains why the pH at the equivalence point of a weak acid-strong base titration is greater than 7?

Accepted Answer

The conjugate base of the weak acid hydrolyzes to produce OH$$^-$$ ions.

Question 9

Which of the following salts will be more soluble in acidic solution than in basic solution?

Accepted Answer

$$\mathrm{$$CaCO_3$$}$$

Question 10

What is the solubility product expression ($$K_{sp}) $$for $$\mathrm{Ba_3$(PO_4$)_2}$$?

Accepted Answer

$$K_{sp} = [Ba$$^{2+}$$]^3 [PO_4$^{3-}]^2$$

Question 11

A solution contains 0.01 M $$\mathrm{$$AgNO_3$$}$$ and 0.20 M $$\mathrm{NH_3$}. $$Given $$K_f$$ for $$\mathrm{Ag(NH_3$)_2^+} is$$ $$1.7 	imes 10^7$, what happens to the concentration of free $$\mathrm{Ag^+}$$ compared to a solution without $$\mathrm{$$NH_3$$}$$?

Accepted Answer

It decreases significantly.

Question 12

Which of the following is true regarding the precipitation of an ionic compound from solution?

Accepted Answer

A precipitate forms when $$Q \u003e K_{sp}.$$

Question 13

Which of the following methods can be used to prepare a buffer solution?

Accepted Answer

Mixing a weak acid with its conjugate base.

Question 14

During the titration of a weak acid with a strong base, what is the pH at the halfway point to the equivalence point?

Accepted Answer

pH = pK_a

Question 15

Which of the following best describes selective precipitation?

Accepted Answer

Separating ions based on their different solubilities in the presence of a common ion.

Question 16

Which of the following is NOT a way to make a buffer?

Accepted Answer

Mixing a strong acid and a strong base.

Question 17

If $$K_{sp}$$ for $$\mathrm{$$CaF_2$$} is$$ $$3.9 	imes 10$$^{-11}$$, what is the molar solubility of $$\mathrm{$$CaF_2$$}$$ in pure water?

Accepted Answer

$$\sqrt[3]{3.9 	imes 10$$^{-11}$$/4}$$

Question 18

Which of the following best explains why $$\mathrm{Ni(OH)_2} is $$more soluble in acidic solution than in basic solution?

Accepted Answer

Acid reacts with $$\mathrm{OH^-}$$, shifting equilibrium to dissolve more $$\mathrm{Ni(OH)_2}.$$

Question 19

Which of the following is true about the effect of adding a common ion to a saturated solution of a sparingly soluble salt?

Accepted Answer

The solubility of the salt decreases.

Chapter 17: Buffers, Titrations, and Solubility Equilibria

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