Question

Human blood contains a buffer of carbonic acid (H_2 CO_3) and bicarbonate anion (HC〖O_3〗^-) in order to maintain blood pH between 7.35 and 7.45, as a value higher than 7.8 or lower than 6.8 can lead to death. In this buffer, hydronium and bicarbonate anion are in equilibrium with carbonic acid. Furthermore, the carbonic acid in the first equilibrium can decompose into CO_2 gas and water, resulting in a second equilibrium system between carbonic acid and water. Because CO_2 is an important component of the blood buffer, its regulation in the body, as well as that of O_2 , is extremely important. The effect of this can be important when the human body is subjected to strenuous condition.

Carbonic acid buffer:
H_2 CO_3 (aq)+ H_2 O(l) ↔H_3 O^+ (aq)+HC〖O_3〗^- (aq)
1. Write the equilibrium constant expression K_c for the carbonic acid buffer in the blood.

Answer 1

Kc = [H3O+][HCO3-] / [H2CO3]

Remember that Kc is products over reactants. Also, you do not include liquid water in a Kc expression, since liquid water has no concentration.