Let's say we're able to decrease concentration of carbon dioxide in blood, how will the pH of the blood be affected?

My Reasoning : Since blood has approximately 92% water, it is safe to assume the carbon dioxide being acidic forms weakly acidic Carbolic acid thereby decreasing the concentration of Protic water resulting in an increased pH, therefore decreasing concentration of carbon dioxide should decrease pH of blood.

However this is not the answer, pH of blood would significantly increase if concentration of carbon dioxide decreases, where am I going wrong? (perhaps hemoglobin has a role?)

  • $\begingroup$ This is a well understood process: en.wikipedia.org/wiki/Respiratory_alkalosis#Mechanism $\endgroup$
    – Zhe
    Oct 22 '17 at 12:20
  • $\begingroup$ You’re wrong at that point where you consider $\ce{H2CO3}$ to be the final species and forget the subsequent deprotonation equilibrium. $\endgroup$
    – Jan
    Oct 22 '17 at 13:19
  • $\begingroup$ Blood has a buffering capacity to maintain a relative stable pH. $\endgroup$ Oct 22 '17 at 20:03
  • $\begingroup$ Google homeostasis. $\endgroup$
    – Todd Minehardt
    Mar 24 '18 at 1:57

Carbonic acid will increase acidity leading to a decrease in pH, not as you have it. It doesn't decrease 'protic water,' but rather it will form an equilibrium with H2O and form carbonic acid, which weakly donates a proton to increase the hydronium ion concentration, thus decreasing pH.

For example, rain is naturally 10X more acidic (pH 6) than neutral water due to the 0.04% CO2 in air.

The pH of blood in theory would increase if we decreased the amount of dissolved CO2 but in reality the human body has an incredibly complex set of mechanisms to maintain the slight BASICITY of blood.


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