$$ \mathrm{pH = -\log(2.0 \times 10^{-5}) = 4.70} $$

$$ [H^+] = [OH^-] = 1.0 \times 10^{-7}~\mathrm{M} $$

$$ \text{Percent ionization} = \frac{[H_3O^+]_{eq}}{[HA]_{initial}} \times 100 $$

Question 1

Which of the following statements best describes the difference between the Arrhenius and Brønsted–Lowry definitions of acids and bases?

Accepted Answer

Arrhenius acids increase hydrogen ion concentration in water, while Brønsted–Lowry acids are proton donors.

Question 2

Which of the following equations correctly represents the autoionization of water?

Accepted Answer

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

Question 3

A solution has $$[H^+] = 2.0 	imes 10$$^{-5}$$~\mathrm{M}. $$What is its pH?

Accepted Answer

$$ \mathrm{pH = -\log(2.0 	imes 10^{-5}) = 4.70} $$

Question 4

Which of the following is true for a neutral aqueous solution at 25°C?

Accepted Answer

$$ [H^+] = [OH^-] = 1.0 	imes 10^{-7}~\mathrm{M} $$

Question 5

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

Accepted Answer

NaCH3COO

Question 6

Which of the following is the correct expression for the acid dissociation constant ($$K_a) $$for acetic acid ($$CH_3COOH) in $$water?

Accepted Answer

$$ K_a = \frac{[CH_3COO^-][H_3O^+]}{[CH_3COOH]} $$

Question 7

A 0.10 M solution of formic acid ($$HCOOH) $$has a pH of 2.38. What is the percent ionization of formic acid in this solution?

Accepted Answer

$$ 4.2\% $$

Question 8

Which of the following best explains why $$HClO_4 is a $$stronger acid than $$HClO$$?

Accepted Answer

Perchloric acid has more oxygen atoms, which increases the oxidation state of chlorine and stabilizes the conjugate base.

Question 9

Which of the following is a Lewis acid but not a Brønsted–Lowry acid?

Accepted Answer

$$ BF_3 $$

Question 10

Which of the following statements about polyprotic acids is correct?

Accepted Answer

The first proton is always easier to remove than the second.

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

A 0.15 M solution of ammonia ($$NH_3) $$has a $$K_b of$$ $$1.8 	imes 10$$^{-5}$$. What is the pH of the solution? (Assume x$$ \ll 0.15$$)

Accepted Answer

$$ \mathrm{pH = 11.20} $$

Question 13

Which of the following factors does NOT increase the strength of a binary acid HX?

Accepted Answer

Decreasing the electronegativity of X across a period.

Question 14

Which of the following ions will make an aqueous solution acidic?

Accepted Answer

$$ [Fe(H_2O)_6]^{3+} $$

Question 15

Which of the following best explains why carboxylic acids are generally stronger acids than alcohols?

Accepted Answer

The carboxylate anion is stabilized by resonance.

Question 16

Which of the following is the correct formula for calculating the percent ionization of a weak acid?

Accepted Answer

$$ 	ext{Percent ionization} = \frac{[H_3O^+]_{eq}}{[HA]_{initial}} 	imes 100 $$

Question 17

Which of the following best describes the effect of increasing the number of oxygen atoms in an oxyacid?

Accepted Answer

It increases the acid strength by stabilizing the conjugate base.

Question 18

Which of the following is a correct statement about the pH scale?

Accepted Answer

A solution with pH 3 is 100 times more acidic than a solution with pH 5.

Acid–Base Equilibria: General Chemistry Study Notes

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