bananabread There's only a few formulas in chem (most of them are given to you in the question or data book) but you need to know which ones to use. One very handy hack to infer the formula is to look at the units, since you often have units cancelling out giving you the correct final units eg if you have a heat of combstion in kJ/mol and you have a mass of a fuel in g, you first convert the mass into mol, then multiply by the heat of combustion to find the energy released. It works like so:
g / (g/mol) = mol
mol x kJ/mol = kJ
