Given the yield is 98%
The reaction is
8H2S(g)+4O2(g)→ S8(l)+8H2O(g)
As per balanced equation eight moles of H2S will react with four moles of O2 to give one mole of S8
Let us calculate the moles of each reactant from given masses
30.0 grams of h2s
Moles = Mass / Molar mass = 30 / 34 = 0.88 moles
They need 0.44 moles of O2 to react
As 50.0 grams of o2 are given so
Moles = Mass / Molar mass = 50 / 16 = 3.125 moles
Thus H2S is the limiting reagent
8 moles of H2S will give one mole of S8
So 0.88 moles of H2S will give = 1 X 0.88 / 8 moles of S8 = 0.11 moles
However the yield is 98% so the actual moles of S8 formed = 0.98 X 0.11 = 0.1078 moles of S8
Mass of S8 produced = Moles X molar mass = 0.1078 X 256
= 27.6 grams of S8