Question 1

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

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

Given the reaction: $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, write the equilibrium constant expression $$K_c.$$

Accepted Answer

$$K_c = \frac{[NH_3$]^2}{[N_2$][H_2$]^3}$$

Question 3

For the reaction $$\mathrm{2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)}$$, $$\Delta n is$$:

Accepted Answer

$$\Delta n = -1$$

Question 4

If the equilibrium constant $$K_c$$ for a reaction is much greater than 1, what does this indicate about the reaction at equilibrium?

Accepted Answer

Products are favored.

Question 5

Which of the following changes will shift the equilibrium to the right for an exothermic reaction?

Accepted Answer

Decreasing the temperature

Question 6

Which of the following is a Brønsted–Lowry acid?

Accepted Answer

$$\mathrm{HCl}$$

Question 7

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

Accepted Answer

$$pH = 2$$

Question 8

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

Accepted Answer

$$\mathrm{HF}$$ and $$\mathrm{NaF}$$

Question 9

Calculate the pH of a buffer solution containing $$0.20\ \mathrm{M}$$ acetic acid ($$\mathrm{CH_3COOH}$$, $$pK_a = 4.76) $$and $$0.10\ \mathrm{M}$$ sodium acetate ($$\mathrm{CH_3COONa}).$$

Accepted Answer

$$pH = 4.46$$

Question 10

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

Accepted Answer

The addition of an ion common to an equilibrium decreases the solubility of a salt.

Question 11

What is the $$K_{sp}$$ expression for the dissolution of $$\mathrm{AgCl(s)}$$?

Accepted Answer

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

Question 12

A solution has $$[H^+] = 1.0 	imes 10$$^{-5}$$\ \mathrm{M}. $$What is its pH?

Accepted Answer

$$pH = 5$$

Question 13

Which of the following is true about the relationship between $$K_a$$ and $$K_b$$ for a conjugate acid-base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 14

If the equilibrium for a reaction is reversed, what happens to the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c is $$inverted ($$1/K_c).$$

Question 15

Which of the following is a Lewis acid?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 16

A $$0.10\ \mathrm{M}$$ solution of a weak acid ($$K_a = 1.8 	imes 10$$^{-5}$$) has a pH closest to:

Accepted Answer

$$pH = 2.87$$

Question 17

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

Accepted Answer

$$pH = 7$$

Question 18

Which of the following will NOT affect the position of equilibrium for a chemical reaction?

Accepted Answer

Adding a catalyst

Question 19

Which salt will have its solubility increased in an acidic solution?

Accepted Answer

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

Question 20

If $$K_c = 4$$ for a reaction, what is $$K_c$$ for the same reaction multiplied by 2?

Accepted Answer

$$K_c = 16$$

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

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