DAT DAT - Dental Admission General Chemistry: Acid-Base Chemistry 2 — Questions and Answers
Question 1: A buffer solution resists pH changes upon addition of small amounts of:
- Water only
- Strong acid or strong base (Correct answer)
- Additional buffer components
- Neutral salts
Correct answer: Strong acid or strong base
A buffer resists pH changes when small amounts of strong acid or strong base are added by neutralizing them through its weak acid/conjugate base equilibrium.
Question 2: The Henderson-Hasselbalch equation for a buffer is: pH =
- pKa + log([A⁻]/[HA]) (Correct answer)
- pKa − log([HA]/[A⁻])
- Ka × [HA]/[A⁻]
- log([HA] + [A⁻])
Correct answer: pKa + log([A⁻]/[HA])
The Henderson-Hasselbalch equation pH = pKa + log([A⁻]/[HA]) relates buffer pH to the pKa and ratio of conjugate base to weak acid.
Question 3: Which combination forms an effective buffer?
- HCl and NaCl
- NaOH and NaCl
- CH₃COOH and CH₃COONa (Correct answer)
- H₂SO₄ and Na₂SO₄
Correct answer: CH₃COOH and CH₃COONa
An effective buffer requires a weak acid and its conjugate base, such as acetic acid (CH₃COOH) and sodium acetate (CH₃COONa).
Question 4: The bicarbonate buffer system in blood maintains physiological pH at approximately:
- 6.0
- 7.4 (Correct answer)
- 8.0
- 5.5
Correct answer: 7.4
The H₂CO₃/HCO₃⁻ buffer system is the primary blood buffer, maintaining pH at approximately 7.4 (normal range 7.35–7.45).
Question 5: A buffer is most effective when the solution pH is close to:
- 7.0 for all buffers
- The pKa of the weak acid component (Correct answer)
- 14
- The numerical value of Ka
Correct answer: The pKa of the weak acid component
A buffer provides maximum buffering capacity when pH is within ±1 unit of the weak acid's pKa.
Question 6: What happens to pH when the buffer capacity is exceeded by addition of a large amount of strong base?
- pH remains constant
- pH increases dramatically once the buffer capacity is exhausted (Correct answer)
- pH decreases
- The solution converts to pure water
Correct answer: pH increases dramatically once the buffer capacity is exhausted
Once all the weak acid component is consumed, additional strong base causes a sharp, dramatic increase in pH.
DAT DAT - Dental Admission General Chemistry: Acid-Base Chemistry 2
A buffer solution resists pH changes upon addition of small amounts of: