A limiting reagent problem since amounts are given for BOTH reactants.
2Na + O2 ==> Na2O
mols Na = grams/molar mass
mol O2 (is this at STP?). Assuming it is mols O2 = L/22.4 = ?
Convert mols Na to mols Na2O using the coefficients in the balanced equation.
Do the same for O2.
It is likely the two values will not b the same which means one of them is wrong. The correct answer in limiting reagent problems is ALWAYS the smaller value and the reagent producing that value is the limiting reagent.
Convert the smaller value to grams Na2O. g = mols x molar mass.