AP Chemistry Flashcards: Properties Of Buffers

What this deck covers

This deck focuses on Properties Of Buffers, giving you a quick way to review the definitions, rules, and examples that matter most for AP Chemistry.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the buffer capacity?

Answer: The amount of acid or base a buffer can neutralize before pH changes significantly. Measures how much acid/base can be added before breakdown.

Flashcard 2: What is the pH of a buffer if $pK_a = 6.5$ and $[\text{A}^-]/[\text{HA}] = 10$?

Answer: pH = 7.5. Using Henderson-Hasselbalch: pH = 6.5 + log(10) = 7.5.

Flashcard 3: What is the maximum buffer capacity condition?

Answer: When $[\text{HA}] = [\text{A}^-]$ and pH = $pK_a$. Equal concentrations provide optimal neutralization for both directions.

Flashcard 4: How is the $pK_a$ of a buffer related to its effective pH range?

Answer: The effective range is $pK_a \pm 1$. Buffers work within one pH unit of their $pK_a$.

Flashcard 5: What does the term 'buffer action' refer to?

Answer: The ability of a buffer to resist pH change. Describes the mechanism by which buffers maintain pH.

Flashcard 6: How does temperature affect buffer pH?

Answer: Temperature can affect the dissociation of the acid/base, altering pH. Temperature changes $K_a$ values, shifting equilibrium.

Flashcard 7: What happens to buffer effectiveness when $[\text{HA}]$ and $[\text{A}^-]$ are equal?

Answer: The buffer is most effective; pH = $pK_a$. Equal concentrations optimize both acid and base neutralization.

Flashcard 8: What is the relationship between buffer concentration and buffer capacity?

Answer: Higher concentrations increase buffer capacity. More buffer molecules available for neutralization reactions.

Flashcard 9: What components make up a typical buffer solution?

Answer: A weak acid and its conjugate base, or a weak base and its conjugate acid. The pair must have weak acid/base relationship for buffering action.

Flashcard 10: Calculate the pH of a buffer with $[\text{HA}] = 0.20$ M, $[\text{A}^-] = 0.05$ M, $pK_a = 4.75$.

Answer: pH = 4.15. Using Henderson-Hasselbalch: pH = 4.75 + log(0.05/0.20).

Flashcard 11: What happens to buffer effectiveness when $[\text{HA}]$ and $[\text{A}^-]$ are equal?

Answer: The buffer is most effective; pH = $pK_a$. Equal concentrations optimize both acid and base neutralization.

Flashcard 12: Identify the weak acid in the buffer: NH₄Cl/NH₃.

Answer: NH₄^+$ (ammonium ion). NH₄⁺ donates protons as the weak acid component.

Flashcard 13: What is the pH of a solution with $[\text{HA}] = [\text{A}^-]$ and $pK_a = 5.00$?

Answer: pH = 5.00. When concentrations are equal, pH equals $pK_a$ exactly.

Flashcard 14: Identify the role of the conjugate base in a buffer.

Answer: The conjugate base neutralizes added acids. A⁻ reacts with H⁺ to prevent pH decrease.

Flashcard 15: Determine the pH change when 0.01 M HCl is added to 1 M acetate buffer.

Answer: Minimal pH change; buffer resists pH change. High buffer concentration overwhelms the small acid addition.

Flashcard 16: Find the pH of a buffer with $pK_a = 5.00$, $[\text{HA}] = 0.05$ M, $[\text{A}^-] = 0.10$ M.

Answer: pH = 5.30. Using Henderson-Hasselbalch: pH = 5.00 + log(0.10/0.05).

Flashcard 17: Which buffer component neutralizes added H⁺ ions?

Answer: The conjugate base of the buffer. A⁻ accepts protons from added acid.

Flashcard 18: Why are buffers important in biochemical systems?

Answer: They maintain stable pH, crucial for enzyme activity. Enzymes require specific pH ranges for optimal activity.

Flashcard 19: How does a buffer maintain a nearly constant pH?

Answer: By neutralizing added acids or bases with its components. Weak acid/base equilibrium maintains constant H⁺ concentration.

Flashcard 20: Calculate the pH of a buffer with $[\text{HA}] = 0.10$ M, $[\text{A}^-] = 0.10$ M, $pK_a = 4.75$.

Answer: pH = 4.75. Equal concentrations make log term zero, so pH = $pK_a$.

Flashcard 21: What effect does adding a strong base have on a buffer?

Answer: The buffer neutralizes it, minimizing pH change. Weak acid consumes OH⁻, preventing pH rise.

Flashcard 22: Which solution is a buffer: NaOH/NaCl or NH₄Cl/NH₃?

Answer: NH₄Cl/NH₃. NH₄⁺/NH₃ is a weak acid/base pair; NaOH/NaCl is not.

Flashcard 23: How does a buffer solution differ from a neutral solution?

Answer: A buffer resists pH changes; a neutral solution does not. Buffers actively resist pH change through chemical equilibrium.

Flashcard 24: What is the primary purpose of a buffer solution?

Answer: To resist changes in pH upon addition of small amounts of acid or base. Buffers maintain pH stability through weak acid/base equilibrium.

Flashcard 25: Choose the buffer pair: HCl/NaCl or CH₃COOH/CH₃COONa?

Answer: CH₃COOH/CH₃COONa. Acetic acid is weak; HCl is strong and cannot buffer.

Flashcard 26: Identify the role of the weak acid in a buffer.

Answer: The weak acid neutralizes added bases. HA reacts with OH⁻ to prevent pH increase.

Flashcard 27: Which property of a buffer determines its capacity?

Answer: The concentrations of the acid and conjugate base. Higher concentrations provide more buffering molecules.

Flashcard 28: What is the effect of dilution on buffer capacity?

Answer: Dilution decreases buffer capacity. Fewer buffer molecules means less neutralization ability.

Flashcard 29: What is the effect of adding a salt of the weak acid to a buffer?

Answer: It increases buffer capacity. More conjugate base increases neutralization ability.

Flashcard 30: Which property is enhanced by equal concentrations of buffer components?

Answer: Buffer capacity is maximized. Equal amounts optimize neutralization in both directions.