The Carbonate buffer system is very important in regulating blood pH levels. Car
ID: 509024 • Letter: T
Question
The Carbonate buffer system is very important in regulating blood pH levels. Carbonic acid is diprotic and therefore has two Ka values: H_2CO_3(aq) H^+(aq) + HCO^-_3(aq) K_a1 = 4.2 times 10^-7 HCO^-_3(aq) H^+(aq) + CO^-2_3(aq) K_a2 = 4.8 times 10^-11 Since the second dissociation has a K_a value significantly smaller than that of the first dissociation, it can be assumed to have no effect on the H_2CO_3(aq)/HCO^-_3-(aq) equilibrium. The pH of blood is 7.4. What is the ratio of carbonic acid to bicarbonate ion in blood?Explanation / Answer
pKa1 = - log (4.2 x 10^-7)
pKa1 = 6.38
pKa2 = 10.32
pH = pKa + log [conjugate base / acid]
7.40 = 6.38 + log [HCO3- / H2CO3]
[HCO3- / H2CO3] = 10.54
ratio of [H2CO3 / HCO3-] = 0.0948