In the chemical reaction below there are 7.8 moles of Mg and 4.7 moles of 02 2 Mg(s) + Oz(g) => 2 MgO a) How many moles of O2 do we need to use all of the Mg? b) How many moles of Mg do we need to use all of the O2? c) Which is the limiting reagent? d) Which is the excess reactant? e) How many moles of MgO can be produced from the limiting reactant?