Final answer:
The best buffer for physiological pH in human blood is the conjugate pair H2PO4-/HPO42- with a pKa of 7.1 as it is closest to the physiological pH level and can maintain a stable pH when strong acids or bases are added.
Step-by-step explanation:
When designing experiments to study the action of pharmacological agents at physiological pH for use in human blood, which of the following conjugate pairs would serve as the best buffer solution? The best buffer would be the one with a pKa closest to the physiological pH.
Considering the options provided and the pH of human blood, which is around 7.3 to 7.4, the conjugate pair H2PO4-/HPO42- with a pKa of 7.1 is the most suitable because its pKa is very close to the physiological pH. According to the Henderson-Hasselbalch equation, a buffer has its maximal buffering capacity when the pH is near the pKa of the acid in the conjugate acid/base pair. Therefore, this pair will enable the maintenance of a stable pH when strong acids or bases are added, which is critical for physiological conditions in human blood.