I think you mean:
".. reacts with oxygen gas to produce lead (II) oxide and 'sulfur' dioxide..."
The balanced chemical reaction would be
2PbS + 3O2 --> 2PbO + 2SO2
The stiochiometric ratio is this: 3 moles of O2 produces 2 moles of lead (II) oxide. So,
0.500 moles (2/3) = 0.333 moles
Therefore, 0.333 moles of PbO is produced when 0.500 moles of O2 reacts with PbS.