Virtual Labs

Determination of pKa Values via Titration

1. Which of the following best defines the pKa of an acid?

a: The concentration of hydrogen ions in the solution. Explanation

Explanation

b: The negative logarithm of the acid dissociation constant (Ka). Explanation

Explanation

c: The pH at which the acid is completely dissociated. Explanation

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d: The ratio of the conjugate base to the undissociated acid. Explanation

Explanation

2. In a titration of a weak acid with a strong base, why is the half-equivalence point significant?

a: Because the acid is fully neutralized. Explanation

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b: Because the pH is equal to 7 at this point. Explanation

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c: Because the pH equals the pKa of the acid. Explanation

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d: Because the buffering capacity is at its minimum. Explanation

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3. Which statement correctly describes the buffering region in a titration curve of a weak acid?

a: The pH increases sharply as soon as the titrant is added. Explanation

Explanation

b: The pH remains nearly constant even with the addition of small amounts of titrant. Explanation

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c: The pH is at its minimum value. Explanation

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d: The acid is completely converted into its conjugate base. Explanation

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4. What does the Henderson-Hasselbalch equation relate in the context of acid-base titration?

a: The volume of titrant added to the concentration of the acid. Explanation

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b: The pH, pKa, and the ratio of the concentrations of the conjugate base to the acid. Explanation

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c: The initial pH of the acid solution and the equivalence point pH. Explanation

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d: The acid dissociation constant and the strength of the titrant. Explanation

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5. If the buffering region of a weak acid titration is observed around pH 4.75, what is the approximate pKa of the acid?

a: 2.0 Explanation

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b: 4.75 Explanation

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c: 7.0 Explanation

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d: 9.0 Explanation

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6. Which of the following describes the overall shape of a titration curve for a weak acid titrated with a strong base?

a: A rapid increase in pH from the start with no buffering region. Explanation

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b: A gradual increase in pH, followed by a flat buffering region, and then a steep rise near the equivalence point. Explanation

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c: A constant pH throughout the titration. Explanation

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d: A decreasing pH as the titrant is added. Explanation

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7. At the equivalence point of a titration of a weak acid with a strong base, which statement is true?

a: The pH is equal to the pKa of the acid. Explanation

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b: All of the acid has been converted to its conjugate base. Explanation

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c: The buffering capacity is at its maximum. Explanation

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d: The pH remains constant at 7.0 regardless of the acid used. Explanation

Explanation