Final answer:
The ratio of relative masses of copper being 2:1 in two compounds is due to b) copper exhibiting different oxidation states in each compound, with +1 in one and +2 in the other, resulting in different ratios of copper-to-chlorine within the compounds.
Step-by-step explanation:
The ratio of relative masses of copper in both compounds is 2:1 because copper exhibits different oxidation states in the compounds, copper reacts with chlorine to form two different compounds. In one compound, copper is in a +1 oxidation state and combines with chlorine in a 1:1 ratio, forming a compound with a ratio of 0.558 g chlorine to 1 g copper. In the other, copper is in a +2 oxidation state and combines with chlorine in a 1:2 ratio, resulting in a compound with a mass ratio of 1.116 g chlorine to 1 g copper. When you compare these two copper-to-chlorine mass ratios, you find that the ratio of copper masses is a small, whole number, precisely 2 to 1. This is a demonstration of the law of multiple proportions, where for a given mass of chlorine, compound A (with copper in a +1 oxidation state) contains twice the mass of copper as does compound B (with copper in a +2 oxidation state).