Chromium(III) oxide reacts with hydrogen sulfide (H₂S) gas to form chromium(III) sulfide and water:
Cr₂O₃(s) + 3H₂S(g) → Cr₂S₃(s) + 3H₂O(l)
To produce 421 g of Cr₂S₃, how many
(b) grams of Cr₂O₃ are required?