Stoichiometry A . STOICIOMETRY DEFENITION Stoichiometry is the study of the quantitative relationships or ratios between two or more substances undergoing a physical change or chemical change (chemical reaction ). Stoichiometry is the calculation of relative quantities of reactan and product in chemical reaction B. Factors to Stoichiometry Balance the equation. Convert units of a given substance to moles. Using the mole ratio, calculate the moles of substance yielded by the reaction. Convert moles of wanted substance to desired units. C. Formula 1.The gram formula mass can be used as a conversion factor in stoichiometric calculations through the following equation: Moles = 2.Volume of a Gas and Moles n = with P representing pressure in atm, V representing volume in liters, T representing temperature in Kelvins, and R the gas constant, which equals .0821 L-atm/mol-K. Given P , V , and