Students X and Y, both prepared an oxide of copper by combining copper and oxygen in the ratios of 4 : 1 and 8 : 2, respectively. Do their results justify the Law of Constant Proportions? Explain. [Pg. No. 167]

We already know that according to the law of constant proportions, a pure compound always contains the same elements combined in a fixed ratio by mass, regardless of the method of preparation or source.

Given,

Student X prepared copper oxide with copper : oxygen ratio = 4 : 1

Student Y prepared copper oxide with copper : oxygen ratio = 8 : 2 = 4 : 1

Hence, it can be concluded that both students obtained the same mass ratio of copper to oxygen (4 : 1).

Yes, the results justify the Law of Constant Proportions because the ratios 4 : 1 and 8 : 2 are equivalent. After simplification, both give the same ratio 4 : 1, showing that copper oxide has a fixed composition by mass.