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

$$K_b = \frac{1.0 \times 10$$^{-14}$$}{1.8 \times 10$$^{-5}$$} = 5.6 \times 10$$^{-10}$$

Question 1

Which of the following is the correct equilibrium expression for the reaction: $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)} in $$terms of concentrations ($$K_c$$)?

Accepted Answer

$$K_c = \frac{[NO_2$]^2}{[N_2O_4]}$$

Question 2

For the reaction $$\mathrm{2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)}$$, if $$K_p = 4.5 at a $$certain temperature, what does this value indicate about the position of equilibrium?

Accepted Answer

The reaction strongly favors products at equilibrium.

Question 3

Given the following reactions and their equilibrium constants:

$$\mathrm{A \rightleftharpoons B}$$, $$K_1 = 2.0$

$$\mathrm{B \rightleftharpoons C}$$, K_2$ = 3.0$$

What is the equilibrium constant for $$\mathrm{A \rightleftharpoons C}$$?

Accepted Answer

$$K = 6.0$$

Question 4

A reaction mixture contains $$[A] = 0.10\ \mathrm{M}$$, $$[B] = 0.20\ \mathrm{M}$$, and $$[C] = 0.30\ \mathrm{M}$$ for the reaction $$\mathrm{A + 2B \rightleftharpoons 3C}. If$$ $$K_c = 5.0$$, what is the value of the reaction quotient $$Q$$ and in which direction will the reaction proceed?

Accepted Answer

$$Q = \frac{[C]^3}{[A][B]^2} = \frac{(0.30)^3$}{(0.10)(0.20)^2$} = 6.75$$, reaction proceeds toward reactants.

Question 5

If the equilibrium constant for a reaction is $$K = 1.2 	imes 10$$^{-7}$$ and the initial concentration of reactant is 0.50$$\ \mathrm{M}$$, which method is most appropriate for solving for equilibrium concentrations?

Accepted Answer

Use the 'x is small' approximation.

Question 6

Which of the following changes will NOT affect the position of equilibrium for the reaction $$\mathrm{2NO_2(g) \rightleftharpoons N_2O_4(g)}$$?

Accepted Answer

Adding a catalyst.

Question 7

Which of the following is a Brønsted–Lowry base but NOT an Arrhenius base?

Accepted Answer

$$NH_3$$

Question 8

Identify the conjugate acid of $$HCO_3$$^-$$.

Accepted Answer

$$H_2CO_3$$

Question 9

Which of the following salts will produce a basic solution when dissolved in water?

Accepted Answer

$$NaC_2H_3O_2$$

Question 10

Calculate the pH of a $$0.010\ \mathrm{M}$$ $$HCl$$ solution at $$25^\circ C.$$

Accepted Answer

$$pH = 2.0$$

Question 11

Which of the following statements is TRUE regarding the effect of temperature on equilibrium?

Accepted Answer

Increasing temperature favors the endothermic direction.

Question 12

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

Accepted Answer

$$K_b = \frac{1.0 	imes 10$$^{-14}$$}{1.8 	imes 10$$^{-5}$$} = 5.6 	imes 10$$^{-10}$$

Question 13

Which of the following is NOT a strong acid?

Accepted Answer

$$HF$$

Question 14

A $$0.020\ \mathrm{M}$$ solution of $$Ba(OH)_2 is $$prepared. What is the pOH of the solution?

Accepted Answer

$$pOH = 1.40$$

Question 15

Which of the following best describes the effect of adding an inert gas at constant volume to a reaction at equilibrium?

Accepted Answer

It does not affect the position of equilibrium.

Question 16

For the reaction $$\mathrm{2NO_2(g) \rightleftharpoons N_2O_4(g)}$$, how will the equilibrium shift if the volume of the container is decreased?

Accepted Answer

Shift toward $$N_2O_4.$$

Question 17

Which of the following is the correct conjugate base for $$H_2SO_4$$?

Accepted Answer

$$HSO_4$$^-$$

Question 18

A solution is prepared by dissolving $$NH_4Cl in $$water. Which of the following best describes the resulting solution?

Accepted Answer

The solution is acidic because $$NH_4$$^+$$ hydrolyzes to produce H$$^+$$.

Question 19

Which of the following is the correct $$K_p$$ expression for the reaction $$\mathrm{2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)}$$?

Accepted Answer

$$K_p = \frac{(P_{SO_3$})^2$}{(P_{SO_2$})^2$ (P_{O_2$})}$$

Chemical Equilibrium, Acids, Bases, and Salt Solutions: Exam 3 Study Guide

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