Q: A solution contains 0.10 M $$\mathrm{CaF}_2 at $$equilibrium. What is the $$K_{sp}$$ for $$\mathrm{CaF}_2$$?

$$K_{sp} = 4.0 \times 10$$^{-4}$$

Question 1

Which of the following best describes the composition of a buffer solution?

Accepted Answer

A weak acid and its conjugate base or a weak base and its conjugate acid

Question 2

What is the Henderson-Hasselbalch equation for calculating the pH of a buffer solution?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log \left( \dfrac{[\mathrm{A}^-]}{[\mathrm{HA}]} \right)$$

Question 3

A buffer is prepared by mixing 0.10 M acetic acid ($$\mathrm{CH}_3\mathrm{COOH}) $$and 0.10 M sodium acetate ($$\mathrm{CH}_3\mathrm{COONa}). If $$the $$K_a of $$acetic acid is $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer?

Accepted Answer

$$\mathrm{pH} = 4.74$$

Question 4

Which of the following statements about buffer capacity is correct?

Accepted Answer

Buffer capacity is highest when the concentrations of the conjugate acid and base are equal and high.

Question 5

If 1.0 mL of 0.10 M NaOH is added to 100 mL of a buffer containing 0.10 M acetic acid and 0.10 M sodium acetate, what will happen to the pH compared to adding the same amount of NaOH to pure water?

Accepted Answer

The pH will increase slightly in the buffer, but much more in pure water.

Question 6

Which of the following is true regarding the effective pH range of a buffer?

Accepted Answer

It is typically $$\mathrm{p}K_a \pm 1$$

Question 7

Which of the following conditions will cause a buffer to lose its ability to resist changes in pH?

Accepted Answer

When one component is less than 10% the concentration of the other

Question 8

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

Accepted Answer

All the weak acid has been converted to its conjugate base

Question 9

Which equation correctly relates the $$K_w$$, $$K_a$$, and $$K_b of a $$conjugate acid-base pair?

Accepted Answer

$$K_w = K_a 	imes K_b$$

Question 10

A solution contains 0.10 M $$\mathrm{CaF}_2 at $$equilibrium. What is the $$K_{sp}$$ for $$\mathrm{CaF}_2$$?

Accepted Answer

$$K_{sp} = 4.0 	imes 10$$^{-4}$$

Question 11

Which of the following will increase the solubility of a salt containing a basic anion in water?

Accepted Answer

Adding a strong acid

Question 12

If $$Q_{sp} \u003e K_{sp}$$ for a solution, what will happen?

Accepted Answer

A precipitate will form

Question 13

Which of the following is a correct expression for the solubility product constant ($$K_{sp}) of$$ $$\mathrm{AgCl}$$?

Accepted Answer

$$K_{sp} = [\mathrm{Ag}^+][\mathrm{Cl}^-]$$

Question 14

Which of the following is a real-life example of a buffer system in the human body?

Accepted Answer

Carbonic acid-bicarbonate system in blood

Question 15

Which of the following is true about polyprotic acids?

Accepted Answer

They donate protons in a stepwise fashion, each with its own $$K_a$$

Question 16

What is the effect of adding a common ion to a saturated solution of a slightly soluble salt?

Accepted Answer

It decreases the solubility of the salt due to the common ion effect

Question 17

Which of the following best explains why acidic oceans lead to the breakdown of coral reefs?

Accepted Answer

Acidic conditions increase the solubility of $$\mathrm{CaCO}_3$$, causing coral skeletons to dissolve

Question 18

Which of the following is a correct statement about the formation of complex ions?

Accepted Answer

Formation of complex ions can increase the solubility of certain salts

Question 19

Which equation represents the formation constant ($$K_f) $$for the complex ion $$\mathrm{Ag(NH_3$)_2^+}$$?

Accepted Answer

$$K_f = \dfrac{[\mathrm{Ag(NH_3$)_2^+}]}{[\mathrm{Ag}^+][\mathrm{NH_3$}]^2}$$

Aqueous Equilibria: Buffers, Titrations, and Solubility

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