Determine the stoichiometric ratio of moles of any reactant to moles of CO2. For instance, if your equation is CaC03 + 2HCL => CaCl2 + CO2 + H2O, then the ratio of moles of CaCO3 to CO2 is 1:1. For every mole of CaCO3 that you are using, you have one mole of CO2.
