stoichiometry of NOâ‚‚ to Oâ‚‚ is 4:1
4 mol of NO₂ reacts with 1 mol of O₂
we need to first find the limiting reactant. limiting reactant is the reactant that is fully consumed during the reaction and amount of product formed depends on the amount of limiting reactant present.
If limiting reactant is Oâ‚‚, there are 2 mol of Oâ‚‚, then NOâ‚‚ present should be 8 mol. However only 2 mol of NOâ‚‚ is present, therefore NOâ‚‚ is the limiting reactant.
the stoichiometry of NO₂ to HNO₃ is 4:4 therefore 1:1
number of NOâ‚‚ moles reacted = number of HNO₃ molesÂ
Number of HNO₃ moles = 2 mol
mass of HNO₃ = 2 mol x 63 g/mol
            = 126 g