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What is the name of a substance that produces an electrically conducting solution when dissolved in water?
What is the name of a substance that produces an electrically conducting solution when dissolved in water?
Electrolyte
What is the term used for substances that do not form electrically conducting solutions when dissolved in water?
What is the term used for substances that do not form electrically conducting solutions when dissolved in water?
Nonelectrolytes
A strong electrolyte exists in solution almost entirely as ions.
A strong electrolyte exists in solution almost entirely as ions.
True
A weak electrolyte fully dissociates into ions when dissolved in water.
A weak electrolyte fully dissociates into ions when dissolved in water.
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Which of the following are considered the most common electrolytes?
Which of the following are considered the most common electrolytes?
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Which two main concepts are used to explain acid-base behavior?
Which two main concepts are used to explain acid-base behavior?
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According to the Bronsted-Lowry concept, what is defined as a species that donates a proton in a proton-transfer reaction?
According to the Bronsted-Lowry concept, what is defined as a species that donates a proton in a proton-transfer reaction?
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What is defined as a species that accepts a proton in a proton-transfer reaction?
What is defined as a species that accepts a proton in a proton-transfer reaction?
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In a conjugate acid-base pair, what is defined as the species that can donate a proton?
In a conjugate acid-base pair, what is defined as the species that can donate a proton?
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In a conjugate acid-base pair, what is defined as the species that can accept a proton?
In a conjugate acid-base pair, what is defined as the species that can accept a proton?
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The Bronsted-Lowry definition of acids and bases is limited to aqueous solutions.
The Bronsted-Lowry definition of acids and bases is limited to aqueous solutions.
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What is an amphoteric compound?
What is an amphoteric compound?
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Every chemical reaction can theoretically be in equilibrium.
Every chemical reaction can theoretically be in equilibrium.
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The acidic or basic nature of salts can be explained using the Bronsted-Lowry concept.
The acidic or basic nature of salts can be explained using the Bronsted-Lowry concept.
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According to the Lewis concept, what is a species that can form a covalent bond by accepting an electron pair from another species?
According to the Lewis concept, what is a species that can form a covalent bond by accepting an electron pair from another species?
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According to the Lewis concept, what is a species that can form a covalent bond by donating an electron pair to another species?
According to the Lewis concept, what is a species that can form a covalent bond by donating an electron pair to another species?
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The formation of what type of ions is considered a Lewis acid-base reaction?
The formation of what type of ions is considered a Lewis acid-base reaction?
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What are the two main factors that influence relative acid strengths?
What are the two main factors that influence relative acid strengths?
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The more polarized the bond is, the more easily the proton is removed, resulting in a weaker acid.
The more polarized the bond is, the more easily the proton is removed, resulting in a weaker acid.
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A larger X atom leads to a weaker bond and stronger acid.
A larger X atom leads to a weaker bond and stronger acid.
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The self-ionization of water is a reaction where two water molecules react to form ions.
The self-ionization of water is a reaction where two water molecules react to form ions.
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What is the ion-product constant for water, denoted as Kw?
What is the ion-product constant for water, denoted as Kw?
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What is the equation for calculating the pH of a solution?
What is the equation for calculating the pH of a solution?
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What is the pH range for a neutral solution?
What is the pH range for a neutral solution?
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What is the pH range for an acidic solution?
What is the pH range for an acidic solution?
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The pH scale is linear.
The pH scale is linear.
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What is the equation for the relationship between pH and pOH?
What is the equation for the relationship between pH and pOH?
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Weak acids and bases dissociate or ionize to a small extent.
Weak acids and bases dissociate or ionize to a small extent.
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What is the equation for the acid ionization constant, Ka?
What is the equation for the acid ionization constant, Ka?
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A larger Ka value signifies a weaker acid.
A larger Ka value signifies a weaker acid.
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A smaller pKa value corresponds to a weaker acid.
A smaller pKa value corresponds to a weaker acid.
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Polyprotic weak acids contain multiple acidic protons that can sequentially dissociate.
Polyprotic weak acids contain multiple acidic protons that can sequentially dissociate.
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A larger Kb value indicates a stronger base.
A larger Kb value indicates a stronger base.
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Study Notes
Chemical Equilibrium in Electrolytes
- Electrolytes are substances that produce electrically conductive solutions when dissolved in water.
- Nonelectrolytes do not produce conductive solutions.
- Strong electrolytes dissociate almost entirely into ions in solution (e.g., HCl + H₂O → H₃O⁺ + Cl⁻).
- Weak electrolytes dissolve in water to produce an equilibrium between the molecular substance and a small amount of ions (e.g., NH₃ + H₂O ⇌ NH₄⁺ + OH⁻).
- Common electrolytes include acids, bases, salts, and water.
Acid-Base Concepts
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Brønsted-Lowry concept:
- An acid donates a proton (H⁺) in a proton-transfer reaction.
- A base accepts a proton in a proton-transfer reaction.
- Conjugate acid-base pairs: Acid and base that differ by one proton (e.g., HCl and Cl⁻; H₂O and H₃O⁺).
- Amphoteric compounds (ampholytes) can act as both acids and bases (e.g., H₂O).
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Lewis concept:
- An acid accepts an electron pair to form a covalent bond.
- A base donates an electron pair to form a covalent bond.
- Coordinate (dative) covalent bonds form in Lewis acid-base reactions (e.g., BF₃ + NH₃ → F₃B:NH₃).
Acid-Base Reactions
- Every chemical reaction can be in equilibrium, and every reaction is reversible.
- Acidity and basicity depend on the reaction partner.
- HNO₃ + H₂O ⇌ NO₃⁻ + H₃O⁺
- H₂O + NH₃ ⇌ OH⁻ + NH₄⁺
- CH₃COOH + H₂O ⇌ CH₃COO⁻ + H₃O⁺
Molecular Structure and Acid Strength
- Acid strength relates to the polarity of the bond to which H⁺ is attached; more polarity, easier proton removal.
- The inductive effect influences the polarity.
- H-O-I < H-O-Br < H-O-Cl
- Also depends on the strength of the bond holding the H⁺; weaker bonds result in greater acid strength
- H-F < H-Cl < H-Br < H-I
Lewis Concept - Complex Ions
- The formation of complex ions is a Lewis acid-base reaction (e.g., Cu²⁺ + 4NH₃ ⇌ [Cu(NH₃)₄]²⁺).
Self-Ionization of Water
- Pure water has a very small conductivity due to self-ionization (autoionization):
- H₂O(l) + H₂O(l) ⇌ H₃O⁺(aq) + OH⁻(aq).
- The ion product constant for water (Kw) is 1.0 × 10⁻¹⁴ at 25°C
- Kw = [H₃O⁺][OH⁻]
Ion-Product Constant for Water
- Relationship between [H₃O⁺] and [OH⁻]
- In neutral solutions [H₃O⁺] = [OH⁻] = 1.0 × 10⁻⁷ M
- In acidic solutions [H₃O⁺] > 1.0 × 10⁻⁷ M
- In basic solutions [H₃O⁺] < 1.0 × 10⁻⁷ M
pH of a Solution
- pH = -log[H₃O⁺]
- Neutral pH = 7, Acidic pH < 7, Basic pH > 7
- pH + pOH = 14
Acid Ionization Constant (Ka)
- Weak Acids: Dissociate only slightly in aqueous solutions.
- Ka: Equilibrium constant describing the ionization of a weak acid. The higher the Ka the stronger the acid.
-
pKa: Negative logarithm of Ka (smaller pKa, stronger acid).
- HF (hydrofluoric acid) Ka = 6.8 × 10⁻⁴, pKa = 3.17, HCIO has Ka = 2.9 × 10⁻⁸, pKa = 7.54
Polyprotic Weak Acids
- Weak acids with multiple acidic protons (e.g., H₂CO₃, H₃PO₄).
- Dissociate sequentially, with unique Ka values for each proton.
- H₃PO₄ ⇌ H⁺ + H₂PO₄⁻ , Ka1=6.9 ×10⁻³
- H₂PO₄⁻ ⇌ H⁺ + HPO₄²⁻ , Ka2 = 6.2 ×10⁻⁸
- HPO₄²⁻ ⇌ H⁺ + PO₄³⁻ , Ka3 = 4.8 × 10⁻¹³
Base Ionization Constant (Kb)
- Describes the ionization of a weak base.
- Weak Bases: Dissociate slightly in aqueous solutions.
- Kb= [BH⁺][OH⁻]/[B]
Acid and Base Ionization Constants of Conjugate Acid-Base Pairs
- Ka × Kb = Kw (1 × 10⁻¹⁴ at 25°C).
Tips for Calculating pH
- For calculating the pH of weak acids and bases, use the formulas and equilibrium constants provided to find the hydrogen or hydroxide ion concentration and then use the pH equation. (examples on slide 27 and slide 28)
Solubility of Electrolytes
- Strong electrolytes: Completely dissociate in water (e.g., NaCl).
- Weak electrolytes (slightly soluble salts): Partially dissociate in water, described by the solubility product constant (Ksp); (e.g., AgCl, PbI₂) - Ksp= [Ag⁺][Cl⁻] for AgCl - Ksp = [Pb²⁺][I⁻]² for PbI₂
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Description
Explore the fundamental principles of chemical equilibrium in electrolytes and acid-base theories. Learn about strong and weak electrolytes, the Brønsted-Lowry and Lewis concepts, and the role of amphoteric compounds. Test your knowledge with this comprehensive quiz designed for chemistry students.
