Ionic Equilibrium

Question 1

What is ionic equilibrium?

Answer 1

A: Ionic equilibrium refers to the state in a solution where the concentrations of all ions remain constant over time due to the balance between the forward and reverse reactions.

Question 2

Q: Define pH.

Answer 2

A: pH is the negative logarithm of the hydrogen ion concentration in a solution, given by
pH
=
−
log
⁡
[
𝐻
+
]
pH=−log[H
+
].

Question 3

Q: What is the relationship between pH and pOH?

Answer 3

A: pH and pOH are related by the equation
pH
+
pOH
=
14
pH+pOH=14 at 25°C (298 K).

Question 4

What is the ionization constant of water (
𝐾
𝑤
K
w
​
)?

Answer 4

𝐾
𝑤
K
w
​
is the ionization constant of water, defined as
𝐾
𝑤
=
[
𝐻
+
]
[
𝑂
𝐻
−
]
=
1
×
1
0
−
14
K
w
​
=[H
+
][OH
−
]=1×10
−14
at 25°C

Question 5

Define a strong acid

Answer 5

A strong acid is one that completely dissociates in water, producing a high concentration of hydrogen ions (
𝐻
+
H
+
).

Question 6

Give an example of a strong acid

Answer 6

Hydrochloric acid (HCl) is an example of a strong acid

Question 7

Define a weak acid

Answer 7

A weak acid is one that partially dissociates in water, establishing an equilibrium between the undissociated acid and its ions.

Question 8

Give an example of a weak acid

Answer 8

Acetic acid (CH₃COOH) is an example of a weak acid

Question 9

What is the acid dissociation constant (
𝐾
𝑎
K
a
​
)?

Answer 9

K
a
​
is a measure of the strength of an acid, defined as the equilibrium constant for the dissociation of an acid in water

Question 10

How is pKa related to
𝐾
𝑎
K
a
​
?

Answer 10

pKa=−logK
a
​
. A lower pKa value indicates a stronger acid

Question 11

Define a strong base.

Answer 11

A strong base is one that completely dissociates in water, producing a high concentration of hydroxide ions (
𝑂
𝐻
−
OH
−
).

Question 12

Give an example of a strong base.

Answer 12

Sodium hydroxide (NaOH) is an example of a strong base.

Question 13

Define a weak base

Answer 13

A weak base is one that partially dissociates in water, establishing an equilibrium between the base and its ions.

Question 14

Give an example of a weak base

Answer 14

Ammonia (NH₃) is an example of a weak base.

Question 15

What is the base dissociation constant (
𝐾
𝑏
K
b
​
)?

Answer 15

K
b
​
is a measure of the strength of a base, defined as the equilibrium constant for the dissociation of a base in water.

Question 16

How is pKb related to
𝐾
𝑏
K
b
​
?

Answer 16

pKb=−logK
b
​
. A lower pKb value indicates a stronger base.

Question 17

What is the common ion effect?

Answer 17

The common ion effect is the suppression of the ionization of a weak electrolyte when a strong electrolyte containing a common ion is added to the solution.

Question 18

How does the common ion effect affect solubility?

Answer 18

The common ion effect decreases the solubility of a salt in solution by shifting the equilibrium towards the undissociated form

Question 19

What is the buffer solution?

Answer 19

A buffer solution is one that resists changes in pH when small amounts of an acid or a base are added.

Question 20

How is a buffer solution prepared?

Answer 20

A buffer solution is typically prepared by mixing a weak acid with its conjugate base or a weak base with its conjugate acid.

Question 21

What is the Henderson-Hasselbalch equation for a buffer?

Answer 21

pH

pKa
+
log
⁡
(
[
A
−
]
[
HA
]
)
pH=pKa+log(
[HA]
[A
−
]
​
), where
[
A
−
]
[A
−
] is the concentration of the conjugate base and
[
HA
]
[HA] is the concentration of the acid.

Question 22

Define solubility product (
𝐾
𝑠
𝑝
K
sp
​
).

Answer 22

K
sp
​
is the equilibrium constant for the dissolution of a sparingly soluble salt in water.

Question 23

What is the relationship between solubility and
𝐾
𝑠
𝑝
K
sp
​
?

Answer 23

The solubility of a salt in water is directly related to the square root or cube root (depending on the stoichiometry) of its
𝐾
𝑠
𝑝
K
sp
​
.

Question 24

What happens to the solubility of a salt if a common ion is added?

Answer 24

The solubility of a salt decreases if a common ion is added, due to the common ion effect.

Question 25

Define hydrolysis of salts.

Answer 25

Hydrolysis of salts occurs when a salt reacts with water to form an acidic or basic solution

Question 26

What is the hydrolysis constant ( 𝐾 ℎ K h ​ )?

Answer 26

K h ​ is the equilibrium constant for the hydrolysis of a salt in water.

Question 27

What determines whether a salt solution is acidic, basic, or neutral?

Answer 27

The pH of a salt solution depends on the strengths of the acid and base from which the salt is derived.

Question 28

Give an example of an acidic salt

Answer 28

Ammonium chloride (NH₄Cl) is an example of an acidic salt because it is formed from a strong acid (HCl) and a weak base (NH₃)

Question 29

Give an example of a basic salt.

Answer 29

Sodium acetate (CH₃COONa) is an example of a basic salt because it is formed from a weak acid (CH₃COOH) and a strong base (NaOH)

Question 30

What is the pH of a neutral solution?

Answer 30

The pH of a neutral solution at 25°C is 7

Question 31

Define the concept of degree of dissociation ( 𝛼 α)

Answer 31

The degree of dissociation ( 𝛼 α) is the fraction of the total number of moles of an electrolyte that dissociates into ions in solution.

Question 32

What is Ostwald's dilution law

Answer 32

Ostwald's dilution law relates the dissociation constant ( 𝐾 𝑎 K a ​ ) of a weak electrolyte to its degree of dissociation ( 𝛼 α) and concentration ( 𝑐 c): 𝐾 𝑎 = 𝛼 2 𝑐 1 − 𝛼 K a ​ = 1−α α 2 c ​

Question 33

What is the pH of a 0.01 M HCl solution

Answer 33

The pH of a 0.01 M HCl solution is 2, since HCl is a strong acid and completely dissociates.

Question 34

What is the pOH of a 0.01 M NaOH solution?

Answer 34

The pOH of a 0.01 M NaOH solution is 2, since NaOH is a strong base and completely dissociates

Question 35

Define the term amphoteric.

Answer 35

An amphoteric substance is one that can act as both an acid and a base, depending on the medium.

Question 36

Give an example of an amphoteric substance

Answer 36

Water (H₂O) is an example of an amphoteric substance because it can act as both an acid and a base.

Question 37

What is the role of a salt bridge in a galvanic cell?

Answer 37

A salt bridge maintains electrical neutrality by allowing the exchange of ions between the two half-cells in a galvanic cell.

Question 38

What is the relationship between 𝐾 𝑎 K a ​ and 𝐾 𝑏 K b ​ for a conjugate acid-base pair?

Answer 38

K a ​ ×K b ​ =K w ​ , where 𝐾 𝑤 K w ​ is the ionization constant of water (( 1 \times 10^{-14}

Question 39

What is a titration curve, and what information can it provide?

Answer 39

A titration curve is a plot of the pH of a solution as a function of the volume of titrant added during a titration. It provides information about the equivalence point, the pKa of the acid or base, and the strength of the acid or base being titrated

Question 40

What is a polyprotic acid? Provide an example.

Answer 40

A polyprotic acid is an acid that can donate more than one proton per molecule in a stepwise manner. An example is sulfuric acid (H₂SO₄), which has two dissociation steps.