Q: A solution has $$[\mathrm{H_3O^+}] = 2.0 \times 10$$^{-4}$$\ \mathrm{M}. $$What is the pH of this solution?

$$\mathrm{pH} = -\log(2.0 \times 10$$^{-4}$$) = 3.70$$

Q: A 0.10 M solution of $$\mathrm{Ca(OH)_2} is $$prepared. What is the $$[\mathrm{OH^-}] in $$the solution?

$$[\mathrm{OH^-}] = 2 \times 0.10\ \mathrm{M} = 0.20\ \mathrm{M}$$

Q: A solution has a pH of 3.40. What is the $$[\mathrm{H_3O^+}]$$ concentration?

$$[\mathrm{H_3O^+}] = 10$$^{-3.40}$$ = 4.0 \times 10$$^{-4}$$\ \mathrm{M}$$

Question 1

Which of the following statements best explains why hydrochloric acid (HCl) is classified as a strong acid in water?

Accepted Answer

HCl completely dissociates into H+ and Cl− ions in water, resulting in nearly 100% ionization.

Question 2

Which of the following acids is found in citrus fruits and is used to adjust pH in foods and beverages?

Accepted Answer

Citric acid ($$\mathrm{H_3C_6H_5O_7})$$

Question 3

A solution has $$[\mathrm{H_3O^+}] = 2.0 	imes 10$$^{-4}$$\ \mathrm{M}. $$What is the pH of this solution?

Accepted Answer

$$\mathrm{pH} = -\log(2.0 	imes 10$$^{-4}$$) = 3.70$$

Question 4

Which of the following best describes the Brønsted–Lowry definition of a base?

Accepted Answer

A substance that accepts a proton ($$\mathrm{H^+}) $$from another substance.

Question 5

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

Accepted Answer

Sodium bicarbonate ($$\mathrm{$$NaHCO_3$$})$$

Question 6

Which of the following is the correct expression for the acid ionization constant ($$K_a) $$for acetic acid ($$\mathrm{HC_2H_3O_2}$$)?

Accepted Answer

$$K_a = \frac{[\mathrm{C_2H_3O_2^-}][\mathrm{H_3O^+}]}{[\mathrm{HC_2H_3O_2}]}$$

Question 7

A 0.10 M solution of $$\mathrm{Ca(OH)_2} is $$prepared. What is the $$[\mathrm{OH^-}] in $$the solution?

Accepted Answer

$$[\mathrm{OH^-}] = 2 	imes 0.10\ \mathrm{M} = 0.20\ \mathrm{M}$$

Question 8

Which of the following best explains why HF is a weak acid while HCl is a strong acid?

Accepted Answer

The H–F bond is much stronger than the H–Cl bond, making HF less likely to ionize completely.

Question 9

Which of the following is a Lewis acid?

Accepted Answer

$$\mathrm{BF_3$}$$, because it can accept an electron pair.

Question 10

A solution has a pH of 3.40. What is the $$[\mathrm{H_3O^+}]$$ concentration?

Accepted Answer

$$[\mathrm{H_3O^+}] = 10$$^{-3.40}$$ = 4.0 	imes 10$$^{-4}$$\ \mathrm{M}$$

Question 11

Which of the following best describes the relationship between $$K_a$$ and $$K_b$$ for a conjugate acid–base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 12

Which of the following household substances is most likely to have a pH greater than 10?

Accepted Answer

Household ammonia

Question 13

A 0.10 M solution of a weak acid, HA, has a pH of 4.25. What is the $$K_a of $$the acid?

Accepted Answer

$$K_a = \frac{[\mathrm{H_3O^+}]^2}{[\mathrm{HA}]_{initial}} = \frac{(5.6 	imes 10$$^{-5}$$)^2$$}{0.10} = 3.1 	imes $$10^{-8}$

Question 14

Which of the following best describes the effect of increasing the initial concentration of a weak acid on its percent ionization?

Accepted Answer

Percent ionization decreases as the initial concentration increases.

Question 15

Which of the following is the correct net ionic equation for the neutralization of hydrochloric acid with sodium hydroxide?

Accepted Answer

$$\mathrm{H^+ (aq) + OH^- (aq) \rightarrow H_2O (l)}$$

Question 16

Which of the following best explains why sodium carbonate ($$\mathrm{Na_2CO_3}) is a $$basic salt?

Accepted Answer

The $$\mathrm{CO_3$^{2-}}$$ ion is the conjugate base of a weak acid and hydrolyzes to produce $$\mathrm{OH^-} in $$water.

Question 17

Which of the following is true for a solution where $$[\mathrm{OH^-}] = 1.0 	imes 10$$^{-9}$$\ \mathrm{M} at 25$$°C?

Accepted Answer

The solution is acidic because $$[\mathrm{H_3O^+}] \u003e [\mathrm{OH^-}].$$

Question 18

Which of the following is the correct relationship between pH and pOH at 25°C?

Accepted Answer

$$\mathrm{pH} + \mathrm{pOH} = 14.00$$

Question 19

Which of the following best describes the role of ammonia ($$\mathrm{NH_3$}) in $$the reaction $$\mathrm{NH_3$ + H_2O \rightleftharpoons NH_4$^+ + OH^-}$$?

Accepted Answer

Ammonia acts as a Brønsted–Lowry base by accepting a proton from water.

CH 16 Acids and Bases: Properties, Strength, and Equilibria

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