Ionic Equilibrium Flashcards
What is ionic equilibrium?
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.
Q: Define pH.
A: pH is the negative logarithm of the hydrogen ion concentration in a solution, given by
pH
=
β
log
β‘
[
π»
+
]
pH=βlog[H
+
].
Q: What is the relationship between pH and pOH?
A: pH and pOH are related by the equation
pH
+
pOH
=
14
pH+pOH=14 at 25Β°C (298 K).
What is the ionization constant of water (
πΎ
π€
K
w
β
)?
πΎ
π€
K
w
β
is the ionization constant of water, defined as
πΎ
π€
=
[
π»
+
]
[
π
π»
β
]
=
1
Γ
1
0
β
14
K
w
β
=[H
+
][OH
β
]=1Γ10
β14
at 25Β°C
Define a strong acid
A strong acid is one that completely dissociates in water, producing a high concentration of hydrogen ions (
π»
+
H
+
).
Give an example of a strong acid
Hydrochloric acid (HCl) is an example of a strong acid
Define a weak acid
A weak acid is one that partially dissociates in water, establishing an equilibrium between the undissociated acid and its ions.
Give an example of a weak acid
Acetic acid (CHβCOOH) is an example of a weak acid
What is the acid dissociation constant (
πΎ
π
K
a
β
)?
K
a
β
is a measure of the strength of an acid, defined as the equilibrium constant for the dissociation of an acid in water
How is pKa related to
πΎ
π
K
a
β
?
pKa=βlogK
a
β
. A lower pKa value indicates a stronger acid
Define a strong base.
A strong base is one that completely dissociates in water, producing a high concentration of hydroxide ions (
π
π»
β
OH
β
).
Give an example of a strong base.
Sodium hydroxide (NaOH) is an example of a strong base.
Define a weak base
A weak base is one that partially dissociates in water, establishing an equilibrium between the base and its ions.
Give an example of a weak base
Ammonia (NHβ) is an example of a weak base.
What is the base dissociation constant (
πΎ
π
K
b
β
)?
K
b
β
is a measure of the strength of a base, defined as the equilibrium constant for the dissociation of a base in water.
How is pKb related to
πΎ
π
K
b
β
?
pKb=βlogK
b
β
. A lower pKb value indicates a stronger base.
What is the common ion effect?
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.
How does the common ion effect affect solubility?
The common ion effect decreases the solubility of a salt in solution by shifting the equilibrium towards the undissociated form
What is the buffer solution?
A buffer solution is one that resists changes in pH when small amounts of an acid or a base are added.
How is a buffer solution prepared?
A buffer solution is typically prepared by mixing a weak acid with its conjugate base or a weak base with its conjugate acid.
What is the Henderson-Hasselbalch equation for a buffer?
pH
pKa
+
log
β‘
(
[
A
β
]
[
HA
]
)
pH=pKa+log(
[HA]
[A
β
]
β
), where
[
A
β
]
[A
β
] is the concentration of the conjugate base and
[
HA
]
[HA] is the concentration of the acid.
Define solubility product (
πΎ
π
π
K
sp
β
).
K
sp
β
is the equilibrium constant for the dissolution of a sparingly soluble salt in water.
What is the relationship between solubility and
πΎ
π
π
K
sp
β
?
The solubility of a salt in water is directly related to the square root or cube root (depending on the stoichiometry) of its
πΎ
π
π
K
sp
β
.
What happens to the solubility of a salt if a common ion is added?
The solubility of a salt decreases if a common ion is added, due to the common ion effect.
Define hydrolysis of salts.
Hydrolysis of salts occurs when a salt reacts with water to form an acidic or basic solution
What is the hydrolysis constant (
πΎ
β
K
h
β
)?
K
h
β
is the equilibrium constant for the hydrolysis of a salt in water.
What determines whether a salt solution is acidic, basic, or neutral?
The pH of a salt solution depends on the strengths of the acid and base from which the salt is derived.
Give an example of an acidic salt
Ammonium chloride (NHβCl) is an example of an acidic salt because it is formed from a strong acid (HCl) and a weak base (NHβ)
Give an example of a basic salt.
Sodium acetate (CHβCOONa) is an example of a basic salt because it is formed from a weak acid (CHβCOOH) and a strong base (NaOH)
What is the pH of a neutral solution?
The pH of a neutral solution at 25Β°C is 7
Define the concept of degree of dissociation (
πΌ
Ξ±)
The degree of dissociation (
πΌ
Ξ±) is the fraction of the total number of moles of an electrolyte that dissociates into ions in solution.
What is Ostwaldβs dilution law
Ostwaldβs dilution law relates the dissociation constant (
πΎ
π
K
a
β
) of a weak electrolyte to its degree of dissociation (
πΌ
Ξ±) and concentration (
π
c):
πΎ
π
=
πΌ
2
π
1
β
πΌ
K
a
β
=
1βΞ±
Ξ±
2
c
β
What is the pH of a 0.01 M HCl solution
The pH of a 0.01 M HCl solution is 2, since HCl is a strong acid and completely dissociates.
What is the pOH of a 0.01 M NaOH solution?
The pOH of a 0.01 M NaOH solution is 2, since NaOH is a strong base and completely dissociates
Define the term amphoteric.
An amphoteric substance is one that can act as both an acid and a base, depending on the medium.
Give an example of an amphoteric substance
Water (HβO) is an example of an amphoteric substance because it can act as both an acid and a base.
What is the role of a salt bridge in a galvanic cell?
A salt bridge maintains electrical neutrality by allowing the exchange of ions between the two half-cells in a galvanic cell.
What is the relationship between
πΎ
π
K
a
β
and
πΎ
π
K
b
β
for a conjugate acid-base pair?
K
a
β
ΓK
b
β
=K
w
β
, where
πΎ
π€
K
w
β
is the ionization constant of water (( 1 \times 10^{-14}
What is a titration curve, and what information can it provide?
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
What is a polyprotic acid? Provide an example.
A polyprotic acid is an acid that can donate more than one proton per molecule in a stepwise manner. An example is sulfuric acid (HβSOβ), which has two dissociation steps.
