Question

1. The chemical equation for carbonic acid equilibrium is shown on p600. If this chemical system were to absorb CO₂ what would happen to the pH? If the system were to absorb H⁺ what would happen to the level of CO₂?

2. Explain the loss of CO₂ from the bloodstream in the lungs. How does the amount of interstitial fluid in the lungs affect CO₂ exchange?

Answer 1

1) The carbonic acid equilibrium is represented in the below equation,

CO2 + H2O <------> H2CO3 <-------> HCO3+ + H+

If this system were to absorb CO2, it combines with water to form H2CO3. There would be an increase in the acidic component and therefore the pH will decrease.

If the system were to absorb H+, it would combine with bicarbonate ion to form carbonic acid which in turn disassociates into CO2 and water. So, the level of CO2 will increase.

2) CO2 is carried as carbonic acid in blood stream. In the lungs, carbonic acid disassociates into CO2 and water and exhaled through respiratory passages. If there is pulmonary edema, increase in the amount of interstitial fluid will decrease the rate of diffusion of gases.