p.43
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What types of problems should students be able to solve related to physical chemistry?
Problems related to reaction kinetics, equilibria, and electrochemistry.
p.8
Theories of Acids and Bases
What is the Lewis definition of a base?
A base is an electron-pair donor.
p.6
Conjugate Acid-Base Pairs
What is a conjugate acid?
The species formed when a base gains a proton (H+).
p.28
Buffer Solutions and Their Components
What characterizes an alkaline buffer?
It keeps the pH > 7 and consists of a weak base and a salt of that weak base.
p.21
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What measures the strength of an acid?
The acid dissociation constant (Ka) or its pKa.
p.5
Conjugate Acid-Base Pairs
What are an acid and its corresponding base referred to as?
Conjugate acid-base pairs.
What ion concentration increases when CH3COONa is added?
[CH3COO–] ion concentration increases.
p.6
Conjugate Acid-Base Pairs
What is the relationship between acids and their conjugate bases?
An acid and its conjugate base differ by one proton.
p.8
Theories of Acids and Bases
What do Lewis acids do?
They accept a lone pair of electrons from a Lewis base.
p.30
Buffer Solutions and Their Components
What components make up an acidic buffer solution in the given example?
A mixture of ethanoic acid and sodium ethanoate.
p.3
Theories of Acids and Bases
What does the Arrhenius definition focus on?
The production of H+ ions in water.
p.5
Theories of Acids and Bases
What must a Brønsted acid contain?
At least one ionisable proton.
p.8
Theories of Acids and Bases
What is the Lewis definition of an acid?
An acid is an electron-pair acceptor.
p.28
Buffer Solutions and Their Components
What characterizes an acidic buffer?
It keeps the pH < 7 and consists of a weak acid and a salt of that weak acid.
p.43
Buffer Solutions and Their Components
What skills should students demonstrate in the laboratory?
Conducting and analyzing the results of physical chemistry experiments.
p.15
Concept of pH and Its Measurement
What does pH measure in a solution?
The concentration of hydronium ions.
p.33
Buffer Solutions and Their Components
What components are involved in the general expression for buffer solutions?
A weak acid and its conjugate base.
What effect does the presence of a common ion have on the ionisation of a weak acid or weak base?
It suppresses the ionisation.
p.35
Henderson-Hasselbalch Equation
What formula is used to calculate the pH of a buffer solution?
pH = pKa + log([A⁻]/[HA]).
p.7
Conjugate Acid-Base Pairs
What is a conjugate acid?
The species formed when a base gains a proton.
What is the effect of adding CH3COOH on the equilibrium?
The equilibrium shifts to the right, increasing the dissociation of CH3COOH.
p.14
Ionisation Constant for Water (Kw)
What is the concentration of [H3O+] and [OH–] in a neutral solution?
[H3O+] = [OH–] = 1.00 x 10^-7 M.
p.34
Henderson-Hasselbalch Equation
In the Henderson-Hasselbalch equation, what do [A-] and [HA] represent?
[A-] represents the concentration of the conjugate base and [HA] represents the concentration of the weak acid.
p.13
Acid - Base Properties of Water
What does OH– represent in the context of acid-base properties?
It represents the conjugate base.
p.4
Theories of Acids and Bases
What is an Arrhenius base?
A substance that produces OH⁻ in water.
What happens to the equilibrium when CH3COONa is added?
The equilibrium shifts to the left, decreasing the dissociation of CH3COOH.
p.23
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What does Kb represent in the context of weak bases?
Kb is the equilibrium constant for the ionisation of a base.
p.14
Ionisation Constant for Water (Kw)
What is the ionisation constant of water (Kw) at 25°C?
Kw = [H+][OH–] = 1.0 x 10^-14.
What ion concentration increases when HCl is added?
[H₃O⁺] ion concentration increases.
p.31
Buffer Solutions and Their Components
What is the effect of adding acid to an acidic buffer on the pH?
The majority of the H+ added are removed, keeping the pH approximately constant.
p.17
Concept of pH and Its Measurement
How do you calculate the pH of a strong acid solution?
pH = -log[H+], where [H+] is the concentration of the acid.
p.3
Theories of Acids and Bases
What is an Arrhenius acid?
A substance that produces H+ (H3O+) in water.
p.4
Theories of Acids and Bases
What does the Arrhenius definition pertain to?
It defines acids and bases based on their behavior in water.
p.7
Conjugate Acid-Base Pairs
What do conjugate acid-base pairs consist of?
An acid and its corresponding base that differ by one proton.
p.33
Buffer Solutions and Their Components
What is the general expression for buffer solutions based on a weak acid and its conjugate base?
K = [acid] × [conjugate base]
p.31
Buffer Solutions and Their Components
What happens when a small amount of acid is added to an acidic buffer solution?
Large amounts of ethanoate ions combine with H+ ions to form undissociated ethanoic acid molecules.
p.30
Buffer Solutions and Their Components
What is the reaction for the partial dissociation of ethanoic acid?
CH3COOH (aq) + H2O (l) ⇌ CH3COO– (aq) + H3O+ (aq).
p.1
Acid - Base Equilibria
What is the primary focus of Acid-Base Equilibria?
The balance between acids and bases in a solution.
What is the common ion effect?
The shift in equilibrium caused by the addition of a compound having an ion in common with the dissolved substance.
p.18
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What does Ka represent in acid-base chemistry?
Ka is the equilibrium constant for the ionisation of a weak acid.
p.27
Polyprotic Acids and Their Ionisation
What are polyprotic acids?
Acids that can donate more than one proton per acid molecule.
p.25
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What does K_b represent in acid-base chemistry?
The base dissociation constant.
p.1
Acid - Base Equilibria
What role do conjugate acid-base pairs play in equilibria?
They help maintain the balance between acids and bases in a solution.
p.1
Acid - Base Equilibria
What is the significance of the pH scale in Acid-Base Equilibria?
It measures the acidity or basicity of a solution.
p.1
Acid - Base Equilibria
What is the relationship between pKa and the strength of an acid?
Lower pKa values indicate stronger acids.
p.24
Ionisation Constant for Water (Kw)
What does Kw represent?
The ionization constant of water.
p.7
Conjugate Acid-Base Pairs
What is a conjugate base?
The species formed when an acid loses a proton.
p.6
Conjugate Acid-Base Pairs
What is a conjugate base?
The species formed when an acid donates a proton (H+).
p.9
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What is the ionization percentage of strong acids and bases in water?
100% (completely dissociate).
p.32
Buffer Solutions and Their Components
What happens when a small amount of alkaline H+ ions is added to an acidic buffer solution?
They react with the alkali to form water molecules.
p.34
Henderson-Hasselbalch Equation
What is the formula for the Henderson-Hasselbalch equation?
pH = pKa + log([A-]/[HA])
p.35
Buffer Solutions and Their Components
What does [CH₃COOH] represent in the buffer solution?
The concentration of acetic acid.
p.13
Acid - Base Properties of Water
What does H3O+ represent in the context of acid-base properties?
It represents the conjugate acid.
p.26
Strong vs Weak Acids and Bases
What is a strong acid?
An acid that completely dissociates in water.
p.40
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What is the relationship between degree of dissociation and concentration?
As concentration increases, the degree of dissociation typically decreases for weak acids and bases.
p.27
Polyprotic Acids and Their Ionisation
What occurs during the second dissociation of HA⁻?
HA⁻ (aq) + H₂O (l) ⇌ H₃O⁺ (aq) + A²⁻ (aq) with K_a2.
p.28
Buffer Solutions and Their Components
What is a buffer solution?
A solution that resists changes in pH upon the addition of small amounts of acid or base.
p.7
Conjugate Acid-Base Pairs
How are conjugate acids and bases related?
They are related through the gain or loss of a proton.
What ion concentration increases when CH3COOH is added?
[CH3COOH] concentration increases.
p.9
Strong vs Weak Acids and Bases
What is the chemical equation for the dissociation of potassium hydroxide (KOH) in water?
KOH (s) + H2O (l) → K+ (aq) + OH– (aq)
p.26
Theories of Acids and Bases
What is an acid?
A substance that donates protons (H+) in a chemical reaction.
What does the common ion effect refer to?
The decrease in solubility of a salt when a common ion is added to the solution.
p.36
Buffer Solutions and Their Components
What are the concentrations of acetic acid and acetate ion in the buffer?
[CH3COOH] = 0.700 M and [CH3COO-] = 0.600 M.
p.36
Buffer Solutions and Their Components
What reaction occurs when HCl is added to the buffer solution?
CH3COO- (aq) + H3O+ (aq) → CH3COOH (aq) + H2O (l).
p.26
Buffer Solutions and Their Components
What is the role of acids in buffer solutions?
Acids help maintain pH by neutralizing bases.
p.38
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What approximation can be made regarding the concentrations in the equilibrium expression?
0.700 - x ≈ 0.700 and 0.598 + x ≈ 0.598
What happens to the equilibrium when HCl is added to a solution of CH₃COOH?
The equilibrium shifts to the left, decreasing the dissociation of CH₃COOH.
p.15
Concept of pH and Its Measurement
What factors influence pH?
The concentration and nature of acids and bases.
p.9
Strong vs Weak Acids and Bases
What is the chemical equation for the dissociation of hydrochloric acid (HCl) in water?
HCl (aq) + H2O (l) → H3O+ (aq) + Cl– (aq)
p.15
Concept of pH and Its Measurement
What is the formula for calculating pH?
pH = -log[H+] or pH = -log[H3O+].
What is the effect of increased [H₃O⁺] on the dissociation of acetic acid (CH₃COOH)?
It decreases the dissociation of CH₃COOH.
p.32
Buffer Solutions and Their Components
What is the chemical reaction that occurs in an acidic buffer solution when OH- ions are added?
CH3COOH(aq) + OH-(aq) → CH3COO-(aq) + H2O(l)
p.1
Acid - Base Equilibria
How is the strength of an acid or base determined?
By its ability to donate or accept protons (H+ ions).
p.13
Acid - Base Properties of Water
What is the significance of the autoionisation of water?
It establishes the basis for acid-base chemistry in aqueous solutions.
p.2
Ionisation Constant for Water (Kw)
What is the ionization constant for water (Kw)?
It is the product of the concentrations of H⁺ and OH⁻ ions in water, equal to 1.0 x 10⁻¹⁴ at 25°C.
p.31
Buffer Solutions and Their Components
What is the chemical reaction that occurs in an acidic buffer when acid is added?
CH3COO– (aq) + H+ (aq) → CH3COOH (aq).
p.30
Buffer Solutions and Their Components
What is the reaction for the complete dissociation of sodium ethanoate?
CH3COONa (aq) → CH3COO– (aq) + Na+ (aq).
p.31
Buffer Solutions and Their Components
What ions are primarily involved in maintaining the pH of an acidic buffer solution?
Ethanoate ions (CH3COO–) and H+ ions.
p.32
Buffer Solutions and Their Components
What principle explains the shift of equilibrium when OH- ions are removed from an acidic buffer solution?
Le Chatelier’s principle.
p.27
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What is the relationship between K_a1 and K_a2 for a diprotic acid?
K_a1 > K_a2; the first dissociation constant is always greater than the second.
p.27
Polyprotic Acids and Their Ionisation
What happens during the first dissociation of H₂A?
H₂A (aq) + H₂O (l) ⇌ H₃O⁺ (aq) + HA⁻ (aq) with K_a1.
p.36
Buffer Solutions and Their Components
What is the role of CH3COO- in the buffer solution when HCl is added?
It reacts completely with H3O+.
p.6
Conjugate Acid-Base Pairs
What is the relationship between bases and their conjugate acids?
A base and its conjugate acid differ by one proton.
p.40
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What is the degree of dissociation?
The fraction of a substance that ionizes in solution.
p.25
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What does K_a represent in acid-base chemistry?
The acid dissociation constant.
p.36
Buffer Solutions and Their Components
What happens when 1 ml of 1 M HCl is added to the buffer solution?
It causes a change in pH.
p.35
Buffer Solutions and Their Components
What does [CH₃COO⁻] represent in the buffer solution?
The concentration of sodium acetate.
p.32
Buffer Solutions and Their Components
What is the effect of adding OH- ions on the pH of an acidic buffer solution?
The pH remains approximately constant.
p.18
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What indicates the strength of a weak acid?
The value of Ka; a higher Ka indicates a stronger weak acid.
p.18
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What is the relationship between Ka and weak acid strength?
A higher Ka value corresponds to a stronger weak acid.
p.38
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What is the equilibrium expression for the dissociation of acetic acid (CH₃COOH)?
CH₃COOH + H₂O ⇌ H₃O⁺ + CH₃COO⁻
p.2
Concept of pH and Its Measurement
How is pH measured?
pH is measured on a scale from 0 to 14, indicating the acidity or basicity of a solution.
p.34
Henderson-Hasselbalch Equation
What does the Henderson-Hasselbalch equation calculate?
The pH of a buffer solution composed of a weak acid and its conjugate base.
p.10
Weak vs Weak Acids and Bases
What is a characteristic of weak acids in water?
They dissociate partially and do not fully ionise.
p.13
Ionisation Constant for Water (Kw)
What are the products of water's autoionisation?
H3O+ (hydronium ion) and OH– (hydroxide ion).
p.26
Concept of pH and Its Measurement
What is the pH range of acids?
Acids have a pH less than 7.
p.10
Weak vs Weak Acids and Bases
What happens when ammonia is added to water?
NH₃ (aq) + H₂O (l) ⇌ NH₄⁺ (aq) + OH⁻ (aq)
p.26
Strong vs Weak Acids and Bases
What is a weak acid?
An acid that partially dissociates in water.
p.29
Buffer Solutions and Their Components
What constitutes an alkaline buffer?
A weak base and its conjugate acid, such as ammonia (NH3) and ammonium ion (NH4+).
p.2
Theories of Acids and Bases
What does the Lewis theory state about acids and bases?
Acids are electron pair acceptors and bases are electron pair donors.
p.1
Acid - Base Equilibria
What does the term 'equilibrium' refer to in Acid-Base chemistry?
A state where the rates of forward and reverse reactions are equal.
p.10
Weak vs Weak Acids and Bases
What is the chemical equation for acetic acid dissociating in water?
CH₃COOH (aq) + H₂O (l) ⇌ CH₃COO⁻ (aq) + H⁺ (aq)
p.27
Polyprotic Acids and Their Ionisation
What is an example of a diprotic acid?
H₂A, which can undergo one or two dissociations.
p.22
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
How does pKa relate to acid strength?
As pKa decreases, Ka increases, indicating stronger acid strength.
p.29
Buffer Solutions and Their Components
Give an example of an alkaline buffer.
Ammonia (NH3) and ammonium ion (NH4+).
What is the common ion effect?
The common ion effect is the decrease in solubility of a salt when a common ion is added to the solution.
p.30
Buffer Solutions and Their Components
What characterizes the concentrations in an acidic buffer solution?
Low [H3O+], high undissociated [CH3COOH], and [CH3COO–].
How does the common ion effect influence the degree of dissociation?
It shifts the equilibrium, reducing the degree of dissociation of weak acids or bases.
p.16
Concept of pH and Its Measurement
What does H+ represent in aqueous solutions?
H+ represents H3O+ (hydronium ion).
p.29
Buffer Solutions and Their Components
Give an example of an acidic buffer.
Ethanoic acid (CH3COOH) and ethanoate ion (CH3COO–).
p.2
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What do Ka and Kb represent?
Ka is the acid dissociation constant, and Kb is the base dissociation constant.
p.18
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
What is the ionisation equation for a weak acid HA?
HA (aq) ⇌ H⁺ (aq) + A⁻ (aq)
p.34
Henderson-Hasselbalch Equation
What is pKa in the context of the Henderson-Hasselbalch equation?
The negative logarithm of the acid dissociation constant (Ka) of the weak acid.
p.10
Weak vs Weak Acids and Bases
What is the difference between weak acids and strong acids?
Weak acids partially ionise in water, while strong acids fully ionise.
p.25
Strength of Acids and Bases (Ka, pKa, Kb, pKb)
At 25°C, what is the relationship between K_a and K_b for a conjugate acid-base pair?
K_a × K_b = K_w, where K_w is the ion product of water.
p.29
Buffer Solutions and Their Components
What is a buffer solution?
A solution consisting of two different solutes: a weak acid and its conjugate base or a weak base and its conjugate acid.
p.2
Buffer Solutions and Their Components
What is a buffer solution?
A buffer solution resists changes in pH when small amounts of acid or base are added.
p.26
Conjugate Acid-Base Pairs
What is the relationship between acids and conjugate bases?
When an acid donates a proton, it forms its conjugate base.
p.25
Concept of pH and Its Measurement
How does an increase in [H3O+] affect the pH value?
It decreases the pH value.
p.2
Theories of Acids and Bases
According to the Arrhenius theory, what defines an acid and a base?
An acid produces H⁺ ions in solution, while a base produces OH⁻ ions.
p.29
Buffer Solutions and Their Components
What constitutes an acidic buffer?
A weak acid and its conjugate base, such as ethanoic acid (CH3COOH) and ethanoate ion (CH3COO–).
p.2
Theories of Acids and Bases
What is the Brønsted-Lowry theory of acids and bases?
It defines acids as proton donors and bases as proton acceptors.
