Q: A solution has a pH of 3.0. What is the concentration of hydronium ions, $$[H^+]$$, in this solution?

$$[H^+] = 1.0 \times 10$$^{-3}$$\ \text{M}$$

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

$$2\ \text{H}_2\text{O} (l) \rightleftharpoons \text{H}_3\text{O}^+ (aq) + \text{OH}^- (aq)$$

Q: A buffer solution is prepared by mixing acetic acid ($$\text{HC}_2\text{H}_3\text{O}_2) $$and sodium acetate ($$\text{NaC}_2\text{H}_3\text{O}_2). $$Which equation best describes the pH of this buffer using the Henderson–Hasselbalch equation?

$$\text{pH} = \text{p}K_a + \log \left( \frac{[\text{C}_2\text{H}_3\text{O}_2^-]}{[\text{HC}_2\text{H}_3\text{O}_2]} \right)$$

Q: Which of the following is a weak acid according to the provided tables?

Acetic acid ($$\text{HC}_2\text{H}_3\text{O}_2)$$

Q: A solution is prepared by dissolving sodium carbonate ($$\text{Na}_2\text{CO}_3) in $$water. Based on the origin of the ions, what is the expected pH of the solution?

Basic, because $$\text{CO}_3$$^{2-}$$ is the conjugate base of a weak acid.

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

$$\frac{[H^+]_{eq}}{[HA]_{initial}} \times 100$$

Question 1

Which of the following statements best explains why hydrochloric acid (HCl) is a strong acid in aqueous solution?

Accepted Answer

HCl completely dissociates into H+ and Cl− ions in water.

Question 2

A solution has a pH of 3.0. What is the concentration of hydronium ions, $$[H^+]$$, in this solution?

Accepted Answer

$$[H^+] = 1.0 	imes 10$$^{-3}$$\ 	ext{M}$$

Question 3

Which of the following household substances is most likely to have a pH greater than 10, based on the provided tables?

Accepted Answer

Household ammonia

Question 4

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

Accepted Answer

$$2\ 	ext{H}_2	ext{O} (l) ightleftharpoons 	ext{H}_3	ext{O}^+ (aq) + 	ext{OH}^- (aq)$$

Question 5

A buffer solution is prepared by mixing acetic acid ($$	ext{HC}_2	ext{H}_3	ext{O}_2) $$and sodium acetate ($$	ext{NaC}_2	ext{H}_3	ext{O}_2). $$Which equation best describes the pH of this buffer using the Henderson–Hasselbalch equation?

Accepted Answer

$$	ext{pH} = 	ext{p}K_a + \log \left( \frac{[	ext{C}_2	ext{H}_3	ext{O}_2^-]}{[	ext{HC}_2	ext{H}_3	ext{O}_2]} ight)$$

Question 6

Which of the following best describes why antacids are used to treat heartburn, as shown in the images and text?

Accepted Answer

Antacids neutralize excess stomach acid, raising the pH in the stomach.

Question 7

Which of the following is a weak acid according to the provided tables?

Accepted Answer

Acetic acid ($$	ext{HC}_2	ext{H}_3	ext{O}_2)$$

Question 8

A solution is prepared by dissolving sodium carbonate ($$	ext{Na}_2	ext{CO}_3) in $$water. Based on the origin of the ions, what is the expected pH of the solution?

Accepted Answer

Basic, because $$	ext{CO}_3$$^{2-}$$ is the conjugate base of a weak acid.

Question 9

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

Accepted Answer

$$K_w = K_a 	imes K_b$$

Question 10

A 0.0100 M solution of ammonia ($$	ext{NH}_3) $$has a $$K_b of$$ $$1.80 	imes 10$$^{-5}$$. What is the pH of this solution? (Assume x$$ \ll 0.0100$$)

Accepted Answer

10.73

Question 11

Which of the following best explains why the pH at the equivalence point of a titration between a weak acid and a strong base is greater than 7?

Accepted Answer

The conjugate base of the weak acid hydrolyzes to produce $$	ext{OH}^-$$ ions.

Question 12

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

Accepted Answer

$$\frac{[H^+]_{eq}}{[HA]_{initial}} 	imes 100$$

Question 13

Which of the following best describes the effect of adding sodium acetate ($$	ext{NaC}_2	ext{H}_3	ext{O}_2) to a $$solution of acetic acid ($$	ext{HC}_2	ext{H}_3	ext{O}_2$$)?

Accepted Answer

The equilibrium shifts to the left, decreasing $$[H^+]$$ and increasing pH.

Question 14

Which of the following is true about the pH and pOH of pure water at 25°C?

Accepted Answer

$$	ext{pH} = 	ext{pOH} = 7.00$$

Question 15

Which of the following best describes why water is considered amphoteric?

Accepted Answer

It can act as both an acid and a base depending on the reaction.

Question 16

A buffer solution is most effective when:

Accepted Answer

The concentrations of the weak acid and its conjugate base are approximately equal.

Question 17

Which of the following best describes the pH at the equivalence point when titrating a strong acid with a strong base?

Accepted Answer

The pH is 7 because the resulting salt solution is neutral.

Question 18

Which of the following is the correct relationship between pH and $$[H^+]$$?

Accepted Answer

$$	ext{pH} = -\log [H^+]$$

Aqueous Equilibria: Acids, Bases, and Buffers

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