A compound is composed of element X and hydrogen.Analysis shows the compound to be 80% X by mass,with three times as many hydrogen atoms as X atoms per molecule.Which element is element X?
A)He
B)C
C)F
D)S
E)none of these

Question

Quizplus · Accepted Answer

If we assume a 100 g sample of the compound, then 80 g of X and 20 g of hydrogen are present. Since there are three times as many hydrogen atoms as X atoms per molecule, the ratio of their masses would be 1:3. Since the atomic mass of hydrogen is ~1, the atomic mass of X must be ~3. Thus, the only option that fits this description is carbon (atomic mass ~12).

A Compound Is Composed of Element X and Hydrogen