Question 1

According to the Arrhenius theory, which of the following best describes a base in aqueous solution?

Accepted Answer

A substance that produces hydroxide ions, $$OH^-$$, when dissolved in water.

Question 2

Which of the following equations correctly represents the ionization of acetic acid, $$HC_2H_3O_2$$, in water according to the Brønsted–Lowry theory?

Accepted Answer

$$HC_2H_3O_2(aq) + H_2O(l) \rightleftharpoons H_3O^+(aq) + C_2H_3O_2^-(aq)$$

Question 3

Which of the following substances is amphiprotic?

Accepted Answer

$$HCO_3$$^-$$

Question 4

In the reaction $$NH_3(aq) + H_2O(l$$) \rightleftharpoons $$NH_4^+(aq) + OH^-(aq$$)$$, which species acts as the Brønsted–Lowry acid?

Accepted Answer

$$H_2O$$

Question 5

Which of the following is the correct expression for the acid ionization constant, $$K_a$$, for the ionization of hydrofluoric acid, $$HF(aq)$$?

Accepted Answer

$$K_a = \frac{[H^+][F^-]}{[HF]}$$

Question 6

Which of the following statements best explains why the fluoride ion, $$F^-$$, is not amphiprotic?

Accepted Answer

$$F^-$$ can only accept a proton but cannot donate one because it has no hydrogen to lose.

Question 7

Which of the following best describes a conjugate acid–base pair?

Accepted Answer

Two substances that differ by one hydrogen ion.

Question 8

A solution is found to have a higher concentration of $$OH^-$$ ions than $$H^+$$ ions. Which of the following best describes the solution?

Accepted Answer

Basic

Question 9

Which of the following reactions demonstrates that the Brønsted–Lowry theory is more general than the Arrhenius theory?

Accepted Answer

$$HCl(g) + NH_3$(g) \rightarrow NH_4Cl(s)$$

Question 10

Given the equilibrium $$HNO_2(aq) + H_2O(l$$) \rightleftharpoons $$NO_2^-(aq) + H_3O^+(aq$$)$$, identify the conjugate acid–base pairs.

Accepted Answer

$$HNO_2$$/$$NO_2$$^-$$ and H_2O/H_3O^+$

Question 11

Which of the following best explains why water, $$H_2O$$, is considered amphiprotic?

Accepted Answer

It can both donate and accept a proton depending on the reaction.

Question 12

Which of the following is the correct $$K_a$$ expression for the ionization of nitrous acid, $$HNO_2(aq$$)$$, in water?

Accepted Answer

$$K_a = \frac{[H_3O^+][NO_2$^-]}{[$$HNO_2$$]}$$

Question 13

Which of the following statements is true regarding the relationship between Arrhenius acids and Brønsted–Lowry acids?

Accepted Answer

All Arrhenius acids are also Brønsted–Lowry acids.

Question 14

Which of the following best describes the role of $$NH_3 in $$the reaction $$NH_3(aq) + H_2O(l$$) \rightarrow $$NH_4^+(aq) + OH^-(aq$$)$$ according to the Brønsted–Lowry theory?

Accepted Answer

It acts as a proton acceptor.

Question 15

Which of the following is a correct statement about the acid ionization constant, $$K_a$$?

Accepted Answer

$$K_a is $$the equilibrium constant for the ionization of an acid in water.

Question 16

Which of the following best explains why the equilibrium position for a weak acid, $$HA$$, in water is not completely to the right?

Accepted Answer

The conjugate base, $$A^-$$, is a stronger base than water.

Question 17

Which of the following is the correct Brønsted–Lowry equation for the reaction of sodium hydrogen carbonate, $$NaHCO_3(s$$)$$, with water?

Accepted Answer

$$HCO_3^-(aq) + H_2O(l$$) \rightleftharpoons H_2CO_3(aq) + OH^-(aq)$$

Question 18

Which of the following best describes the role of $$H_2O in $$the reaction $$HF(aq) + H_2O(l) \rightarrow H_3O^+(aq) + F^-(aq)$$?

Accepted Answer

It acts as a Brønsted–Lowry base.

Lesson 8.1: Acid–Base Theories and Equilibrium: The Nature of Acids and Bases

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