How much air is required to completely burn 36 kg of iron (II) disulfide FeS2 to sulfur dioxide? The volume fraction of oxygen in the air is 21%.

1) Let’s compose the reaction equation:
4FeS2 + 11O2 = 2Fe2O3 + 8SO2 ↑
2) Calculate the amount of FeS2 and oxygen:
n (FeS2) = m (FeS2) / M (FeS2) = 36000/120 = 300 mol.
To determine the amount of oxygen, we will compose the proportion according to the reaction equation:
300/4 = n (O2) / 11
n (O2) = 825 kmol.
3) Let’s calculate the volumes of oxygen and air:
V (O2) = n (O2) ∙ Vm = 825 ∙ 22.4 = 18480 l = 18.48 m3
V (air) = V (O2) ∙ 100 / ω (O2) = 18.48 ∙ 100/21 = 88 m3
Answer: 88 m3.

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