Final answer:
The data is an example of the law of definite proportions, which means that the compounds have fixed compositions. The compounds X and Y have the same elements (carbon and hydrogen) but in different ratios, resulting in slightly different properties.
Step-by-step explanation:
The data provided is an example of the law of definite proportions. According to this law, a compound always contains the same elements in the same ratio by mass. Compound X always contains 14.13 g of carbon and 2.96 g of hydrogen, while compound Y always contains 19.91 g of carbon and 3.34 g of hydrogen. Therefore, the ratios of carbon to hydrogen in both compounds are constant.
This data tells us that substances X and Y have fixed compositions. X and Y have the same elements (carbon and hydrogen) but in different ratios, which gives them slightly different properties. These compounds may both be hydrocarbons, but their specific chemical structures and properties would need further analysis to determine.