2H2S (g) + SO2 (g) --------> 2H2O (l) + 3S (s)
According to the reaction equation ,
2 moles of H2S combines with 1 mole of SO2 to give three moles of sulphur.
Therefore, the ratio of moles of H2S , SO2 and S is 2:1:3
Dividing by 4 , we get
H2S : SO2 : S as 0.5 : 0.25 : 0.75
Hence , 0.5 moles of H2S will react with 0.25 moles of SO2 to produce 0.75 moles of sulphur.