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?
30 g of oxygen
Explanation
The Law of Constant Proportions states that a compound always contains the same elements combined in a fixed ratio by mass. Since the compound has 40% sulfur and 60% oxygen by mass, the fixed mass ratio of sulfur to oxygen is 40:60, which simplifies to 2:3. Using this ratio, if sulfur is 20 g, oxygen must be 30 g to maintain the constant proportion.
Solution Steps
Step 1: According to the Law of Constant Proportions, a compound always contains elements in a fixed ratio by mass.
Step 2: Given composition is 40% sulfur and 60% oxygen, so the fixed mass ratio of sulfur to oxygen = 40:60 = 2:3.
Step 3: Let the mass of oxygen in the new sample = x g. Then, 20/x = 2/3.
Step 4: Cross-multiplying gives 2x = 60, so x = 30 g.