$$K_b = 1.4 \times 10$$^{-11}$$

Hydrofluoric acid, $$K_a = 7.2 \times 10$$^{-4}$$

Question 1

Which of the following statements best describes the Brønsted–Lowry definition of acids and bases?

Accepted Answer

An acid is a proton donor, and a base is a proton acceptor.

Question 2

Which of the following is the conjugate base of $$\mathrm{$$HCO_3$$^-}$$?

Accepted Answer

$$\mathrm{CO_3$^{2-}}$$

Question 3

A solution has $$[\mathrm{H_3O^+}] = 2.5 	imes 10$$^{-5}$$\ \mathrm{M}. $$What is the pH of the solution?

Accepted Answer

$$\mathrm{pH} = 4.60$$

Question 4

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

Accepted Answer

$$\mathrm{NaC_6H_5CO_2}$$

Question 5

Given $$K_a$$ for HF is $$7.2 	imes 10$$^{-4}$$, what is the K_b$ for F$$^-$$ at 25$$^\circ\mathrm{C}$$?

Accepted Answer

$$K_b = 1.4 	imes 10$$^{-11}$$

Question 6

Which of the following acids is the strongest, based on their $$K_a$$ values?

Accepted Answer

Hydrofluoric acid, $$K_a = 7.2 	imes 10$$^{-4}$$

Question 7

A $$0.10\ \mathrm{M}$$ solution of lactic acid ($$\mathrm{HC_3H_5O_3}) is$$ $$3.7\%$$ ionized. What is the value of $$K_a$$ for lactic acid?

Accepted Answer

$$K_a = 1.4 	imes 10$$^{-4}$$

Question 8

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

Accepted Answer

The product $$[\mathrm{H_3O^+}][\mathrm{OH^-}] is $$always $$1.0 	imes 10$$^{-14}$$ at 25$$^\circ\mathrm{C}$$.

Question 9

Calculate the pH of a $$0.12\ \mathrm{M}$$ solution of aniline ($$\mathrm{C_6H_5NH_2}$$), given $$K_b = 4.0 	imes 10$$^{-10}$$.

Accepted Answer

$$\mathrm{pH} \approx 8.90$$

Question 10

Which of the following best explains why $$\mathrm{H_2O} is $$considered amphoteric?

Accepted Answer

It can act as both a Brønsted–Lowry acid and a base.

Question 11

A $$0.10\ \mathrm{M}$$ solution of formic acid ($$\mathrm{HCOOH}) $$has a pH of $$2.38. $$What is the percent ionization?

Accepted Answer

$$4.2\%$$

Question 12

Which of the following pairs are conjugate acid-base pairs?

Accepted Answer

$$\mathrm{NH_4$^+}$$ / $$\mathrm{NH_3$}$$

Question 13

Which of the following is true for a solution where $$[\mathrm{OH^-}] = 1.0 	imes 10$$^{-3}$$\ \mathrm{M} at$$ $$25^\circ\mathrm{C}$$?

Accepted Answer

The solution is basic and $$\mathrm{pH} = 11.0$$

Question 14

Which of the following is a property of a strong acid?

Accepted Answer

It ionizes completely in water.

Question 15

Which of the following is the correct relationship between $$K_a$$, $$K_b$$, and $$K_w$$ for a conjugate acid-base pair at $$25^\circ\mathrm{C}$$?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 16

A solution is prepared by dissolving $$0.10\ \mathrm{mol} of$$ $$\mathrm{NH_4Cl} in$$ $$1.0\ \mathrm{L} of $$water. Which statement is correct?

Accepted Answer

The solution will be acidic because $$\mathrm{NH_4$^+}$$ hydrolyzes to produce $$\mathrm{H_3O^+}.$$

Question 17

Which of the following best describes the trend in acid strength for polyprotic acids such as $$\mathrm{H_3PO_4}$$?

Accepted Answer

The first ionization constant $$K_{a,1} is $$greater than $$K_{a,2}$$, which is greater than $$K_{a,3}.$$

Question 18

A buffer solution is prepared using acetic acid and sodium acetate. Which equation correctly represents the equilibrium in this buffer?

Accepted Answer

$$\mathrm{CH_3COOH} (aq) + H_2O (l) \rightleftharpoons CH_3COO^- (aq) + H_3O^+ (aq)$$

Aqueous Equilibria: Acid-Base and Solubility Equilibria

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