Phosphate buffers are important in regulating the pH of intracellular fluids at pH values generally between 7.1 and 7.2.
a. What is the concentration ratio of H2PO4- to HPO4-2 in intracellular fluid at pH = 7.15? H2PO4 2(aq) ⇌ HPO4-2(aq) + H+(aq) Ka = 6.2 × 10-8
b. Why is a buffer composed of H3PO4 and H2PO4- ineffective in buffering the pH of intracellular fluid? H3PO4(aq) ⇌ H2PO4-(aq) + H+(aq) Ka = 7.5 × 10-3