Editing Partial pressure (section)

==Henry's law and the solubility of gases==
{{main|Henry's law}}

Gases will [[solvation|dissolve]] in [[liquid]]s to an extent that is determined by the equilibrium between the undissolved gas and the gas that has dissolved in the liquid (called the ''[[solvent]]'').<ref name=RolfeSander>[http://www.henrys-law.org An extensive list of Henry's law constants, and a conversion tool]</ref> The equilibrium constant for that equilibrium is:
{{NumBlk||<math display="block">k = \frac {p_x}{C_x}</math>|{{EquationRef|1}}}}
where:
*<math>k</math> = &nbsp;the equilibrium constant for the [[solvation]] process
*<math>p_x</math> = &nbsp;partial pressure of gas <math>x</math> in equilibrium with a [[Solution (chemistry)|solution]] containing some of the gas 
*<math>C_x</math> = &nbsp;the concentration of gas <math>x</math> in the liquid solution

The form of the equilibrium constant shows that '''the concentration of a [[solute]] gas in a solution is directly proportional to the partial pressure of that gas above the solution'''. This statement is known as [[Henry's law]] and the equilibrium constant <math>k</math> is quite often referred to as the Henry's law constant.<ref name=RolfeSander/><ref>{{cite journal |author1=Francis L. Smith  |author2=Allan H. Harvey  |name-list-style=amp |date=September 2007 |title=Avoid Common Pitfalls When Using Henry's Law |journal=Chemical Engineering Progress |issn=0360-7275}}</ref><ref>[http://dwb4.unl.edu/Chem/CHEM869J/CHEM869JLinks/www.chem.ualberta.ca/courses/plambeck/p101/p01182.htm Introductory University Chemistry, Henry's Law and the Solubility of Gases] {{webarchive|url=https://web.archive.org/web/20120504234140/http://dwb4.unl.edu/Chem/CHEM869J/CHEM869JLinks/www.chem.ualberta.ca/courses/plambeck/p101/p01182.htm |date=2012-05-04 }}</ref>

Henry's law is sometimes written as:<ref name=UArizona>{{Cite web |url=http://www.chem.arizona.edu/~salzmanr/103a004/nts004/l41/l41.html |title=University of Arizona chemistry class notes |access-date=2006-05-26 |archive-url=https://web.archive.org/web/20120307045555/http://www.chem.arizona.edu/~salzmanr/103a004/nts004/l41/l41.html |archive-date=2012-03-07 |url-status=dead }}</ref>
{{NumBlk||<math display="block">k' = \frac {C_x}{p_x}</math>|{{EquationRef|2}}}}

where <math>k'</math> is also referred to as the Henry's law constant.<ref name=UArizona/> As can be seen by comparing equations ({{EquationNote|1}}) and ({{EquationNote|2}}) above, <math>k'</math> is the reciprocal of <math>k</math>. Since both may be referred to as the Henry's law constant, readers of the technical literature must be quite careful to note which version of the Henry's law equation is being used.

Henry's law is an approximation that only applies for dilute, ideal solutions and for solutions where the liquid solvent does not [[chemical reaction|react chemically]] with the gas being dissolved.