Q: If $$K_a$$ for acetic acid is $$1.8 \times 10$$^{-5}$$, what is the K_b$ for its conjugate base?

$$K_b = 5.6 \times 10$$^{-10}$$

Q: For the reaction $$\ce{CO(g) + 2H2(g) CH3OH(g)}$$, $$\Delta n = -2. If$$ $$K_c = 0.50 at$$ $$298 K$$, what is $$K_p$$? ($$R = 0.08206 L$$·atm/K·mol)

$$K_p = 0.50 \times (0.08206 \times 298$$)^{-2}$$

Question 1

Which of the following statements best describes a system at chemical equilibrium?

Accepted Answer

The forward and reverse reaction rates are equal, and the concentrations of reactants and products remain constant over time.

Question 2

For the reaction $$\ce{N2(g) + 3H2(g)  2NH3(g)}$$, which of the following is the correct expression for the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = \frac{[\ce{NH3}]^2}{[\ce{N2}][\ce{H2}]^3}$$

Question 3

Given the reaction $$\ce{2SO2(g) + O2(g)  2SO3(g)}$$ and $$K_c = 4.0 at a $$certain temperature, what is the value of $$K_c$$ for the reverse reaction?

Accepted Answer

$$K_c = 0.25$$

Question 4

Which of the following changes will shift the equilibrium to the right for the exothermic reaction $$\ce{A(g)  B(g) + C(g)}$$ ($$\Delta H \u003c 0$$)?

Accepted Answer

Decreasing the temperature

Question 5

Which of the following is a Brønsted–Lowry base?

Accepted Answer

$$\ce{NH3}$$

Question 6

What is the pH of a $$0.010 M $$solution of $$\ce{HCl} (a $$strong acid)?

Accepted Answer

$$pH = 2.0$$

Question 7

Which of the following pairs will form a buffer solution when mixed in water?

Accepted Answer

$$\ce{HF}$$ and $$\ce{NaF}$$

Question 8

A $$0.20 M $$solution of a weak acid $$\ce{HA}$$ has a pH of $$2.70. $$What is the value of $$K_a$$ for $$\ce{HA}$$? (Assume $$[\ce{H+}] \approx x)$$

Accepted Answer

$$K_a = 2.0 	imes 10$$^{-5}$$

Question 9

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

Accepted Answer

The addition of an ion common to an equilibrium system decreases the solubility of a weak electrolyte.

Question 10

What is the pH at the equivalence point of a titration between a strong acid and a strong base?

Accepted Answer

$$pH = 7$$

Question 11

Which of the following is the correct $$K_{sp}$$ expression for $$\ce{CaF2 (s)  Ca$$^{2+}$$ (aq) + 2F^- (aq)}$$?

Accepted Answer

$$K_{sp} = [\ce{Ca$$^{2+}$$}][\ce{F^-}]^2$$

Question 12

If $$K_a$$ for acetic acid is $$1.8 	imes 10$$^{-5}$$, what is the K_b$ for its conjugate base?

Accepted Answer

$$K_b = 5.6 	imes 10$$^{-10}$$

Question 13

A buffer is prepared by mixing $$0.10$$ mol of $$\ce{NH3}$$ and $$0.10$$ mol of $$\ce{NH4Cl} in$$ $$1.0 L of $$solution. If $$K_b$$ for $$\ce{NH3} is$$ $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer? (pK_b = 4.74$)

Accepted Answer

$$pH = 9.26$$

Question 14

Which of the following will increase the solubility of $$\ce{AgCl} in $$water?

Accepted Answer

Adding $$\ce{NH3} to $$form a complex ion with $$\ce{Ag^+}$$

Question 15

Which of the following is true about the effect of a catalyst on a system at equilibrium?

Accepted Answer

A catalyst increases the rate at which equilibrium is achieved but does not affect the position of equilibrium.

Question 16

For the reaction $$\ce{CO(g) + 2H2(g)  CH3OH(g)}$$, $$\Delta n = -2. If$$ $$K_c = 0.50 at$$ $$298 K$$, what is $$K_p$$? ($$R = 0.08206 L$$·atm/K·mol)

Accepted Answer

$$K_p = 0.50 	imes (0.08206 	imes 298$$)^{-2}$$

Question 17

Which of the following best describes the relationship between the strengths of a conjugate acid-base pair?

Accepted Answer

The stronger the acid, the weaker its conjugate base.

Question 18

A solution has $$[\ce{H+}] = 3.2 	imes 10$$^{-4}$$ M. What is the pH of the solution?

Accepted Answer

$$pH = 3.49$$

Question 19

Which of the following is a Lewis acid?

Accepted Answer

$$\ce{Al$$^{3+}$$}$$

Question 20

Which of the following statements about the autoionization of water is correct?

Accepted Answer

$$\ce{H2O}$$ acts as both an acid and a base, producing $$\ce{H+}$$ and $$\ce{OH^-}$$ ions.

Exam 2 Study Guide: Chemical Equilibrium, Acid-Base Equilibria, and Aqueous Equilibria

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