I am suffering from this kind of chemistry problems. I think I will have bunch of these in my exam. But I can't understand this kind of problem's solutions. If you know any formula or information about this, please help. How many grams of fluorine gas must react to give 9.26 g of sulfur hexafluoride? What mass of calcium chloride is required to react completely with 5.00 g of sodium phosphate? How many grams of oxygen gas must react to give 6.85 g of calcium oxide? type of problem: how many [gram/mole] must [react/be needed] to [produce/give] x gram of p? The official state of this problem is called [calculate amounts of reactants for a reaction in grams or moles] You do not have to answer to these problems. But if you can give me some procedures about how the answer can be derived, I would appreciate it, because I want to know kind of formula, equation to plug values in it. What I tried is to divide the weight I am given with the formula weight of something...can't go further. Please help.