The pH of blood is 7.35. It is maintained in part by the buffer system composed of carbonic acid (H₂CO₃) and the bicarbonate (hydrogen carbonate, HCO₃⁻) ion. What is the ratio of [bicarbonate]/[carbonic acid] at this pH? For carbonic acid, K_a1 = 4.2 × 10⁻⁷. A)[bicarbonate]/[carbonic acid] = 0.11 B)[bicarbonate]/[carbonic acid] = 0.38 C)[bicarbonate]/[carbonic acid] = 2.65 D)[bicarbonate]/[carbonic acid] = 9.4 E)None of these choices are correct.

Question

Quizplus · Accepted Answer

The Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the base (bicarbonate in this case) and [HA] is the concentration of the acid (carbonic acid), can be used to find the ratio of bicarbonate to carbonic acid. Given that the pH of blood is 7.35 and the pKa of carbonic acid is 6.1 (since Ka = 4.2 × 10^-7, and pKa = -log(Ka)), we can rearrange the equation to solve for the ratio [A-]/[HA]:7.35 = 6.1 + log([bicarbonate]/[carbonic acid])Solving for the ratio gives approximately 9.4, which means the correct answer is D.

The PH of Blood Is 7