Final answer:
The chemical formulas H₂SO₄ (sulfuric acid) and H₂SO₃ (sulfurous acid) obey the Law of Multiple Proportions because they consist of the same elements with the oxygen in differing whole number ratios.
Step-by-step explanation:
The Law of Multiple Proportions states that if two elements form more than one compound, then the ratios of the masses of the second element that combine with a fixed mass of the first element are ratios of small whole numbers. To determine which two chemical formulas obey this law, we have to find a pair of compounds that are composed of the same elements but with differing amounts. In the given options, sulfur and oxygen form two compounds: H2SO4 (sulfuric acid) and H2SO3 (sulfurous acid). These two compounds have the same amount of sulfur (one atom per molecule) but different amounts of oxygen; thus, the ratios of the masses of oxygen that combine with a fixed mass of sulfur are in whole numbers, demonstrating the Law of Multiple Proportions.