Question

A compound consists of 40% sulfur and 60% oxygen by mass. In a sample of the same compound containing 20 g of sulfur, what mass of oxygen must be present to satisfy the Law of Constant Proportions?

Answer 1

30 g of oxygen. Sulfur and oxygen occur in the fixed mass ratio 40:60. Therefore, the oxygen required for 20 g of sulfur is (20 × 60)/40 = 30 g, preserving the compound’s constant composition.