Q: A solution has a pH of 3.0. What is the concentration of hydronium ions in this solution?

$$[H_3O^+] = 1.0 \times 10$$^{-3}$$~M$$

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

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

Question 1

Which of the following statements best describes a Brønsted–Lowry acid?

Accepted Answer

A substance that donates a proton (H+) to another substance.

Question 2

Which of the following is the correct equilibrium expression for the autoionization of water?

Accepted Answer

$$K_w = [H_3O^+][OH^-]$$

Question 3

A solution has a pH of 3.0. What is the concentration of hydronium ions in this solution?

Accepted Answer

$$[H_3O^+] = 1.0 	imes 10$$^{-3}$$~M$$

Question 4

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

Accepted Answer

NaF

Question 5

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

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 6

Which of the following acids is expected to have the highest $$K_a$$ value?

Accepted Answer

Hydrochloric acid ($$HCl)$$

Question 7

A 0.10 M solution of a weak acid has a pH of 2.87. What is the percent ionization of the acid?

Accepted Answer

1.3%

Question 8

Which of the following factors increases the strength of a binary acid HX as you move down a group in the periodic table?

Accepted Answer

Decreasing bond strength

Question 9

Which of the following is a Lewis acid in the reaction $$BF_3$$ + $$NH_3$$ \rightarrow F_3B\cdot $$NH_3$$?

Accepted Answer

$$BF_3$$

Question 10

Calculate the pH of a 0.20 M solution of acetic acid ($$K_a = 1.8 	imes 10$$^{-5}$$). Assume x$$ \ll 0.20$$.

Accepted Answer

2.37

Question 11

Which of the following best explains why $$Fe^{3+}$$ forms an acidic solution in water?

Accepted Answer

It increases the polarity of the O–H bonds in water, making it easier for water to lose $$H^+.$$

Question 12

Which of the following is true for the pH and pOH of a neutral solution at 25°C?

Accepted Answer

$$pH = 7.00$$ and $$pOH = 7.00$$

Question 13

Which of the following weak bases has the highest $$K_b$$ value?

Accepted Answer

Methylamine ($$CH_3NH_2)$$

Question 14

Which of the following statements about polyprotic acids is correct?

Accepted Answer

The first dissociation constant ($$K_{a1}) is $$always larger than the second ($$K_{a2}).$$

Question 15

Which of the following best describes the effect of resonance stabilization on acid strength?

Accepted Answer

It increases acid strength by stabilizing the conjugate base.

Question 16

A solution is prepared by dissolving $$0.10~M$$ $$NH_3 in $$water. What is the pH of the solution? ($$K_b = 1.8 	imes 10$$^{-5}$$, assume x$$ \ll 0.10$$)

Accepted Answer

11.13

Question 17

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

Accepted Answer

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

Question 18

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

Accepted Answer

$$HClO_4$$ has more oxygen atoms, increasing the oxidation state of Cl and stabilizing the conjugate base.

Question 19

Which of the following is a real-world application of acid–base equilibria?

Accepted Answer

The use of antacids to neutralize excess stomach acid.

Acid–Base Equilibria: Concepts, Calculations, and Chemical Structure

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