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Questions and Answers
What happens to the pH of a weak acid solution when a salt containing its conjugate base is added?
What happens to the pH of a weak acid solution when a salt containing its conjugate base is added?
- The pH increases. (correct)
- The degree of dissociation of the weak acid increases.
- The pH remains unchanged.
- The pH decreases significantly.
Which equation is used for calculating pH in buffer solutions?
Which equation is used for calculating pH in buffer solutions?
- Arrhenius equation
- Nernst equation
- Le Chatelier's principle
- Henderson-Hasselbalch equation (correct)
What is the relationship between Ka of an acid and Kb of its conjugate base?
What is the relationship between Ka of an acid and Kb of its conjugate base?
- Ka/Kb = Kw
- Ka - Kb = Kw
- Ka x Kb = Kw (correct)
- Ka + Kb = Kw
What is the result of exceeding the capacity of a buffer solution?
What is the result of exceeding the capacity of a buffer solution?
Why is the quadratic formula often avoided in calculations involving weak acids and bases?
Why is the quadratic formula often avoided in calculations involving weak acids and bases?
What happens to the strength of a weak acid as its $K_a$ value increases?
What happens to the strength of a weak acid as its $K_a$ value increases?
If a weak acid is 0.10 M in solution and dissociates, what is the concentration of $H_3O^+$ at equilibrium if $K_a$ is $4.9×10^{-10}$?
If a weak acid is 0.10 M in solution and dissociates, what is the concentration of $H_3O^+$ at equilibrium if $K_a$ is $4.9×10^{-10}$?
When considering weak acid dissociation, what does the term $K_a$ represent?
When considering weak acid dissociation, what does the term $K_a$ represent?
How is the pH of a weak acid solution calculated at equilibrium?
How is the pH of a weak acid solution calculated at equilibrium?
Which weak acid has the largest $K_a$ value, indicating it is the strongest?
Which weak acid has the largest $K_a$ value, indicating it is the strongest?
What is the expected pH of a $0.10$ M solution of a weak acid with $K_a = 4.9 × 10^{-10}$?
What is the expected pH of a $0.10$ M solution of a weak acid with $K_a = 4.9 × 10^{-10}$?
In the dissociation of a weak acid HA, what is produced alongside $H_3O^+$?
In the dissociation of a weak acid HA, what is produced alongside $H_3O^+$?
When extra acid is added to a buffer solution, what change occurs to the pH?
When extra acid is added to a buffer solution, what change occurs to the pH?
What is the value of the base-dissociation constant, Kb, for NH3 in water?
What is the value of the base-dissociation constant, Kb, for NH3 in water?
Which of the following statements is true regarding the relationship between Ka and Kb?
Which of the following statements is true regarding the relationship between Ka and Kb?
What happens to the pH of a solution when sodium acetate is added to acetic acid?
What happens to the pH of a solution when sodium acetate is added to acetic acid?
What is the concentration of H3O+ ions when the pH is 2.08?
What is the concentration of H3O+ ions when the pH is 2.08?
What is the impact of increasing the Kb value for a weak base?
What is the impact of increasing the Kb value for a weak base?
What type of salt is formed when a strong acid reacts with a weak base?
What type of salt is formed when a strong acid reacts with a weak base?
If the pH of a solution containing NH3 is 11.20, what is the concentration of OH- ions in that solution?
If the pH of a solution containing NH3 is 11.20, what is the concentration of OH- ions in that solution?
When acetic acid dissociates in solution, what are the products formed?
When acetic acid dissociates in solution, what are the products formed?
What is the effect of adding acetate to an acetic acid solution according to Le Châtelier’s Principle?
What is the effect of adding acetate to an acetic acid solution according to Le Châtelier’s Principle?
What is a buffer solution primarily composed of?
What is a buffer solution primarily composed of?
Which of the following statements is true about the buffer capacity?
Which of the following statements is true about the buffer capacity?
What will happen to the pH of a buffer after adding a small amount of strong acid?
What will happen to the pH of a buffer after adding a small amount of strong acid?
How is the pH of a buffer calculated using the Henderson-Hasselbalch equation?
How is the pH of a buffer calculated using the Henderson-Hasselbalch equation?
What is the significance of maintaining a pH of around 7.4 in blood?
What is the significance of maintaining a pH of around 7.4 in blood?
When a hydroxide ion (OH-) is added to the acetic acid-acetate buffer, which of the following occurs?
When a hydroxide ion (OH-) is added to the acetic acid-acetate buffer, which of the following occurs?
Which equation represents the dissociation of acetic acid in water?
Which equation represents the dissociation of acetic acid in water?
What effect does dilution have on buffer capacity?
What effect does dilution have on buffer capacity?
What is the primary role of buffers in biological systems?
What is the primary role of buffers in biological systems?
Flashcards
Acid Dissociation Constant (Ka)
Acid Dissociation Constant (Ka)
A measure of the strength of a weak acid in solution, calculated using the concentrations of hydronium ions and the anion formed by the acid's dissociation.
Weak Acid Dissociation
Weak Acid Dissociation
A weak acid's tendency to donate a hydrogen ion (H+) to form a proton (H3O+). The strength of the acid is indicated by its equilibrium constant (Ka).
Weak Acid Equilibrium Problem
Weak Acid Equilibrium Problem
A mathematical expression used to calculate the concentrations of the various species in a solution of a weak acid at equilibrium, based on the acid's dissociation constant (Ka).
pH of a weak acid solution
pH of a weak acid solution
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Changing the pH of a buffer solution
Changing the pH of a buffer solution
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Buffer Solution
Buffer Solution
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Henderson – Hasselbalch Equation
Henderson – Hasselbalch Equation
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Determining Ka values
Determining Ka values
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Base Dissociation Constant (Kb)
Base Dissociation Constant (Kb)
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Ion Product Constant for Water (Kw)
Ion Product Constant for Water (Kw)
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Common Ion Effect
Common Ion Effect
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Acidic Salt
Acidic Salt
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Basic Salt
Basic Salt
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Neutral Salt
Neutral Salt
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Neutral pH
Neutral pH
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Ka * Kb = Kw
Ka * Kb = Kw
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Henderson-Hasselbalch Equation
Henderson-Hasselbalch Equation
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Dissociation Constant (Ka/Kb)
Dissociation Constant (Ka/Kb)
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Le Châtelier's Principle
Le Châtelier's Principle
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Buffer Capacity
Buffer Capacity
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Weak Acid Buffer
Weak Acid Buffer
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pKa
pKa
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Buffer pH Calculation
Buffer pH Calculation
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Maximum Buffer Capacity
Maximum Buffer Capacity
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pH Stability
pH Stability
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Weak Base Buffer
Weak Base Buffer
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Study Notes
Acids and Bases 2 - Summary
- Equilibrium Concentrations of Weak Acids and Bases: Weak acids and bases partially dissociate in water. Equilibrium calculations determine the concentrations of all species (acid, conjugate base, and hydronium/hydroxide ions) at equilibrium.
- Acid Dissociation Constant (Ka): A measure of a weak acid's strength. A higher Ka indicates a stronger acid. The formula for Ka is [H3O+][A−]/[HA].
- Weak Acid-Dissociation Constants: These constants represent the tendency of various weak acids to dissociate in water at 25°C. Various weak acids (e.g., hydrofluoric, nitrous, benzoic, acetic, hypochlorous, hydrocyanic, phenol) have different Ka values, indicating differing strengths.
- Calculating pH of a Weak Acid: The pH of a weak acid solution can be calculated using its initial concentration and Ka. Approximate calculations often simplify the process due to the low Ka values and the relationship of species concentrations in these systems.
- Common Ion Effect: Adding a salt of a weak acid's conjugate base to a solution of the weak acid reduces its dissociation, slightly shifting the equilibrium, affecting the pH.
- Buffers: Buffer solutions are mixtures of a weak acid and its conjugate base (or a weak base and its conjugate acid). These solutions maintain a relatively constant pH upon the addition of small amounts of acid or base. Important for biological systems.
- Buffer Capacity: The buffer capacity is the maximum amount of acid or base a buffer can neutralize without significantly changing its pH. Capacity increases with the concentration of the components.
- Henderson-Hasselbalch Equation: A useful equation to determine the pH of a buffer solution. The equation is pH = pKa + log( [conjugate base]/[acid]).
- Uses of the Henderson-Hasselbalch Equation: Used for buffer solution pH calculations, as well as calculating the amounts of acid/conjugate needed to make a buffer at a specific pH.
- Weak Base-Dissociation Constants (Kb): Similar to Ka, but for weak bases, reflecting their tendency to dissociate in water.
- Relationship between Ka and Kb: The product of the Ka of a weak acid and the Kb of its conjugate base equals the ionic product of water (Kw). This relationship allows calculation of either constant knowing the other.
Acid-Base Properties of Salts
- Neutral Salt: Results from the reaction of a strong acid and a strong base.
- Acidic Salt: Comes from a strong acid and a weak base.
- Basic Salt: Formed from a weak acid and a strong base.
Equilibrium in Solutions of Weak Acids
- Weak Acid in Water: A weak acid (HA) partially dissociates in water: HA(aq) + H₂O(l) ⇌ H₃O+(aq) + A−(aq) .
- Acid-Dissociation Constant: Ka= [H₃O+][A⁻]/[HA]
Equilibrium in Solutions of Weak Bases
- Weak Base in Water: A weak base (B) reacts with water: B(aq) + H₂O(l) ⇌ BH+(aq) + OH⁻(aq)
- Base-Dissociation Constant: Kb = [BH+][OH⁻]/[B]
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