Q: If $$K_{sp}$$ for $$\mathrm{Mg(OH)_2} is$$ $$5.6 \times 10$$^{-12}$$, what is the molar solubility of $$\mathrm{Mg(OH)_2}$$ in pure water?

$$1.2 \times 10$$^{-4}$$\ \mathrm{M}$$

Question 1

Which of the following statements about the equilibrium constant $$K is $$CORRECT?

Accepted Answer

The value of $$K is $$constant at a given temperature and depends only on the reaction and temperature.

Question 2

For the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, what will happen to the position of equilibrium if the pressure is increased at constant temperature?

Accepted Answer

The equilibrium will shift to the right, favoring the formation of $$\mathrm{NH_3$}.$$

Question 3

Given the reaction $$\mathrm{2HI(g) \rightleftharpoons H_2$(g) + I_2$(g)}$$ with $$K_p = 0.5 at a $$certain temperature, if the initial partial pressure of $$\mathrm{HI} is$$ $$1.0\ \mathrm{atm}$$ and no $$\mathrm{H_2$} or$$ $$\mathrm{I_2$} is $$present, what is the equilibrium partial pressure of $$\mathrm{H_2$}$$?

Accepted Answer

$$0.297\ \mathrm{atm}$$

Question 4

Which of the following changes will INCREASE the solubility of $$\mathrm{Mg(OH)_2} in $$water?

Accepted Answer

Decreasing the pH of the solution.

Question 5

A buffer solution is prepared by mixing $$0.100\ \mathrm{M}$$ acetic acid ($$\mathrm{p}K_a = 4.76) $$and $$0.0850\ \mathrm{M}$$ sodium acetate. What is the pH of the buffer?

Accepted Answer

$$4.87$$

Question 6

Which of the following best describes the effect of adding a common ion to a saturated solution of a sparingly soluble salt?

Accepted Answer

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

Question 7

Which of the following is TRUE regarding the relationship between $$K_c$$ and $$K_p$$ for a gaseous reaction?

Accepted Answer

$$K_p = K_c(RT$$)^{\Delta n}$$, where $$\Delta n$$ is the change in moles of gas.

Question 8

A $$0.10\ \mathrm{M}$$ solution of acetic acid ($$K_a = 1.74 	imes 10$$^{-5}$$) has a pH closest to:

Accepted Answer

$$2.9$$

Question 9

Which of the following statements about Le Chatelier's Principle is INCORRECT?

Accepted Answer

Adding a catalyst increases the value of the equilibrium constant.

Question 10

What is the pH of a $$0.040\ \mathrm{M}$$ solution of $$\mathrm{NaOH}$$?

Accepted Answer

$$12.60$$

Question 11

Which of the following is a correct expression for the solubility product constant ($$K_{sp}) $$for $$\mathrm{$$PbI_2$$}$$?

Accepted Answer

$$K_{sp} = [\mathrm{Pb$$^{2+}$$}][\mathrm{I^-}]^2$$

Question 12

A solution contains $$0.300\ \mathrm{M}$$ acetic acid and $$0.250\ \mathrm{M}$$ sodium acetate. What is the pH? ($$pK_a = 4.76)$$

Accepted Answer

$$4.70$$

Question 13

Which of the following is TRUE about polyprotic acids?

Accepted Answer

Each successive $$pK_a$$ value is higher than the previous one.

Question 14

Which of the following pairs can act as a buffer?

Accepted Answer

$$\mathrm{CH_3COOH}$$ and $$\mathrm{CH_3COONa}$$

Question 15

If $$K_{sp}$$ for $$\mathrm{Mg(OH)_2} is$$ $$5.6 	imes 10$$^{-12}$$, what is the molar solubility of $$\mathrm{Mg(OH)_2}$$ in pure water?

Accepted Answer

$$1.2 	imes 10$$^{-4}$$\ \mathrm{M}$$

Question 16

Which of the following is the correct Henderson-Hasselbalch equation for a buffer solution?

Accepted Answer

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

Question 17

Which of the following is the correct relationship between $$K_a$$, $$K_b$$, and $$K_w$$ for a conjugate acid-base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 18

A $$0.050\ \mathrm{M}$$ solution of $$\mathrm{NH_3$}$$ ($$pK_b = 4.75) $$has a pH closest to:

Accepted Answer

$$11.4$$

Question 19

Which of the following best explains why molality is preferred over molarity when preparing solutions at varying temperatures?

Accepted Answer

Molality is based on mass, which does not change with temperature, while molarity is based on volume, which can expand or contract.

Question 20

Which of the following is the correct expression for the reaction quotient $$Q$$ for the reaction $$aA + bB \rightleftharpoons cC + dD$$?

Accepted Answer

$$Q = \frac{[C]^c[D]^d}{[A]^a[B]^b}$$

Chemical Equilibrium, Solutions, Acids & Bases, and Buffers: Study Notes

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