I found the following definition of Henry's Law in my textbook:
"The partial pressure of the gas in vapour phase is proportional to the mole fraction of the gas in the solution."
(a) Why should the undissolved gas be in vapour phase?
(b) As i understand it, a gas is called a vapour if it is below its critical temperature.
(c) But from other sources on the Internet (such as Wikipedia )there is no such restriction on the temperature for Henry's law to hold[I mean the temperature is not supposed to be below the critical temperature of gas to use Henry's law].
(d) Can a gas above it's critical temperature be dissolved in a liquid?
(a) I am having trouble understanding why the word vapour phase is used in the definition. Although I do understand what Henry's Law is trying to say.
(b) I tried to search all over the internet but could not find any satisfactory answer.