The balanced chemical equation:
2 ZnS + 3 O₂ → 2 ZnO + 2 SO₂
1 mole of any gas at STP occupies 22.4 L
?? mole of O₂ gas at STP will occupy 12.6 L
we have 0.5625 mole of O₂
From the balanced equation we see that:
2 moles of ZnS react with 3 moles O₂
?? mole ZnS react with 0.5625 mole O₂
Number of moles of ZnS = 0.375 mol
mass of ZnS = 0.375 * 97.45 (Molar mass) = 36.5 g ZnS