In the following reaction, how many grams of ferrous sulfide (FeS) will produce 0.56 grams of iron (III) oxide (Fe2O3)? 4FeS + 7O2 → 2Fe2O3 + 4SO2 The molar mass of ferrous sulfide is 87.92 grams and that of iron (III) oxide is 159.7 grams.