1. The problem statement, all variables and given/known data This is not a problem, per se, because it is part of my Lab. We're calculating the standard enthalpy change of formation for solid Ammonium Chloride. To do this, we're using four separate rxns, and totaling their individual standard enthalpy change of formations. For two of these reactions we're using literature values, but I can not find the literature value for the standard enthalpy change of formation for aqueous Hydrogen Chloride online or in my book -- I can only find the lit value for gaseous Hydrogen Chloride. As far as I know, there is no way to convert one to the other, because these are determined experimentally, so I need to know the lit value for aqueous Hydrogen Chloride. Am I just missing something, or does anyone have a place where I can look this up? 2. Relevant equations 3. The attempt at a solution Google and my text book.