Editing Carbonic acid (section)

===In biological solutions===
In the presence of the enzyme [[carbonic anhydrase]], equilibrium is instead reached rapidly, and the following reaction takes precedence:<ref name="Lindskog_1997">{{cite journal |vauthors=Lindskog S |year=1997 |title=Structure and mechanism of carbonic anhydrase |journal=Pharmacology & Therapeutics |volume=74 |issue=1 |pages=1–20 |doi=10.1016/S0163-7258(96)00198-2 |pmid=9336012}}</ref> <chem display=block>HCO3^- {+} H^+ <=> CO2 {+} H2O</chem>

When the created carbon dioxide exceeds its solubility, gas evolves and a third equilibrium <chem display=block>CO_2 (soln) <=> CO_2 (g)</chem> must also be taken into consideration. The equilibrium constant for this reaction is defined by [[Henry's law#Fundamental types and variants of Henry's law constants|Henry's law]]. 

The two reactions can be combined for the equilibrium in solution: <math chem="" display="block">\begin{align}
\ce{HCO3^{-}{} + H+{} <=> CO2(soln){} + H2O} && K_3 = \frac{[\ce{H+}][\ce{HCO3^-}]}{[\ce{CO2(soln)}]}
\end{align}</math> When Henry's law is used to calculate the denominator '''care is needed''' with regard to units since Henry's law constant can be commonly expressed with 8 different dimensionalities.<ref>{{Cite journal |last=Sander |first=Rolf |last2=Acree |first2=William E. |last3=Visscher |first3=Alex De |last4=Schwartz |first4=Stephen E. |last5=Wallington |first5=Timothy J. |date=2022-01-01 |title=Henry’s law constants (IUPAC Recommendations 2021) |url=https://www.degruyter.com/document/doi/10.1515/pac-2020-0302/html |journal=Pure and Applied Chemistry |language=en |volume=94 |issue=1 |pages=71–85 |doi=10.1515/pac-2020-0302 |issn=1365-3075|doi-access=free}}</ref>