My school book (NCERT) states Henry's Law as: The solubility of a gas in a liquid is directly proportional to the partial pressure of the gas present above the surface of liquid or solution. and then says that the most commonly used form of Henry’s law states that: “the partial pressure of the gas in vapour phase (p) is proportional to the mole fraction of the gas (x) in the solution” and is expressed as $p=K_Hx$
then on Wikipedia, Chemistry LibreTexts and on google search result Henry's law is stated as:
$$C = K_HP$$
and Chemistry LibreTexts also says:
Henry's law describes the dependence of the vapor pressure of a solute as a function of its concentration. In terms of mole fraction χ2: $$\lim_{\chi_2\rightarrow0}\left( \frac{p}{\chi_2}\right) =K_H$$
which is same as the $p=K_Hx$ described in my school book. My teacher said both definitions are correct
So my question is:
Why Henry's law has been defined in two ways (mathematically) and why in both ways the proportionality constant is called Henry's constant?
