Chapter 2

Question 1

What is an electrolyte?

Answer 1

Compounds that dissolve in water to form a solution that conducts electricity.

Question 2

What is a nonelectrolyte?

Answer 2

Compounds that dissolve in water to form a solution that does not conduct electricity.

Question 3

Give an example of an electrolyte.

Answer 3

NaCl

Question 4

Give an example of a nonelectrolyte.

Answer 4

Sucrose

Question 5

What are strong electrolytes?

Answer 5

Substances that ionize completely in a solvent.

Question 6

What are weak electrolytes?

Answer 6

Substances that ionize only partially in a solvent.

Question 7

Define an acid according to the Brønsted-Lowry theory.

Answer 7

A proton donor.

Question 8

Define a base according to the Brønsted-Lowry theory.

Answer 8

A proton acceptor.

Question 9

What is formed when an acid loses a proton?

Answer 9

A conjugate base.

Question 10

What is formed when a base accepts a proton?

Answer 10

A conjugate acid.

Question 11

What are amphiprotic species?

Answer 11

Species that can act either as acids or bases.

Question 12

What is the hydronium ion?

Answer 12

H3O+

Question 13

What principle states that the position of a chemical equilibrium shifts to relieve applied stress?

Answer 13

Le Châtelier’s Principle.

Question 14

What does the equilibrium constant expression exclude?

Answer 14

Pure liquids, pure solids, or solvents present in excess.

Question 15

What is the solubility-product constant represented by?

Answer 15

Ksp

Question 16

What happens to the solubility of an ionic precipitate when a common ion is added?

Answer 16

The solubility decreases.

Question 17

What is the relationship between Ka and Kb for conjugate acid-base pairs?

Answer 17

Ka * Kb = 1 x 10^-14.

Question 18

What is the assumption made when [H3O+] &laquo_space;cHA?

Answer 18

The contribution of H3O+ from the weak acid dominates.

Question 19

What is the pKw at 25 °C?

Answer 19

14.00

Question 20

What are the concentrations of H3O+ and OH- in pure water at 25 °C?

Answer 20

[H3O+] = [OH-] = 1.00 x 10^-7

Question 21

What is the dissociation reaction for water?

Answer 21

H2O ⇌ H3O+ + OH-

Question 22

What indicates that chemical equilibrium is a dynamic state?

Answer 22

The rates of the forward and reverse reactions are identical.

Question 23

What is the formula for calculating hydronium ion concentration from a weak acid’s dissociation?

Answer 23

[H3O+] = Ka * cHA

Question 24

What is the effect of a strong acid on H3O+ concentration compared to a weak acid?

Answer 24

A strong acid produces a higher concentration of H3O+.

Question 25

What is a conjugate acid?

Answer 25

The species formed when a base accepts a proton.

Question 26

What is the effect of temperature on chemical equilibrium?

Answer 26

Changes in temperature can disturb chemical equilibria.

Question 27

What is the significance of the Ksp value?

Answer 27

It allows us to calculate the solubility of a substance in water.

Question 28

What is the typical pH range of blood?

Answer 28

Between 7.35 and 7.45.

Question 29

What happens to the equilibrium position when a system is stressed?

Answer 29

It shifts in a direction that relieves the stress.

Question 30

Fill in the blank: A conjugated base is formed when an acid loses a _______.

Answer 30

proton

Question 31

Fill in the blank: A conjugated acid is formed when a base _______ a proton.

Answer 31

accepts

Question 32

True or False: All acids are strong electrolytes.

Answer 32

False

Question 33

True or False: Weak acids dissociate completely in water.

Answer 33

False

Question 34

When can we assume that [OH–] << cHA?

Answer 34

If Kb ≤ 10–5 ## Footnote This assumption simplifies the calculations.

Question 35

When can we not assume that [OH–] << cHA?

Answer 35

If Kb ≥ 10–4 ## Footnote This indicates significant ionization.

Question 36

What is a buffer solution?

Answer 36

A solution that resists changes in pH upon dilution or addition of acids/bases ## Footnote Buffers are crucial in many chemical applications.

Question 37

What components are needed to prepare a buffer system?

Answer 37

A conjugate acid-base pair ## Footnote This combination is vital for maintaining pH.

Question 38

What is the equilibrium expression for a weak acid HA in water?

Answer 38

HA + H2O ⇌ H3O+ + A– ## Footnote This reaction illustrates the dissociation of weak acids.

Question 39

How does dilution affect the pH of a buffer solution?

Answer 39

pH remains independent until concentrations are too low ## Footnote Excessive dilution reduces buffering capacity.

Question 40

What happens to the pH when strong acids or bases are added to a buffer?

Answer 40

Buffer capacity reduces, leading to significant pH changes ## Footnote The effectiveness of the buffer is compromised.

Question 41

What is buffer capacity?

Answer 41

The number of moles of strong acid/base causing a 1.00-unit pH change in 1.00 L of buffer ## Footnote Defined mathematically as β = -d[H3O+]/d(pH).

Question 42

What is the optimum buffer capacity ratio of conjugate acid to base?

Answer 42

cNaA/cHA = 1 ## Footnote This ratio provides maximum buffering efficiency.

Question 43

What is the practical method for preparing buffer solutions?

Answer 43

Combine calculated quantities of conjugate acid-base pairs and adjust pH with strong acid/base ## Footnote Use a pH meter for accuracy.

Question 44

How might you prepare a 500.0 mL pH 4.5 buffer solution?

Answer 44

Combine 1.0 M acetic acid (HAc) and solid sodium acetate (NaAc) ## Footnote Adjust the proportions to achieve the desired pH.