What is the difference between stoichiometry and gas stoichiometry?
You definitely need to understand the concepts behind regular stoichiometry before you can do gas stoichiometry properly. Regular stoichiometry refers to the general idea of moles and the ratios between different reactants and products in a balanced chemical reaction equation. Gas stoichiometry refers more to the ideal gas law PV = nRT and associated reactions (basically reactions involving gases which we assume are ideal).