From the balanced chemical equation:
2CuFeS2 + 5O2 → 2Cu + 2FeO + 4SO2
We can see that for every 5 moles of oxygen (O2) that react, 4 moles of sulfur dioxide (SO2) are produced. Therefore, we can use a proportion to calculate the number of moles of O2 required to produce 12 moles of SO2:
5 moles O2 : 4 moles SO2 = x moles O2 : 12 moles SO2
Cross-multiplying, we get:
5 moles O2 x 12 moles SO2 = 4 moles SO2 x (x moles O2)
60 = 4x
x = 15
Therefore, 15 moles of O2 are required to generate 12 moles of SO2 gas.