Question

Two compounds are tested for mass composition. Compound X contains 15.0 grams hydrogen and 120.0 grams oxygen. Compound Y contains 2.0 grams of hydrogen and 32.0 grams of oxygen. Are compound X and compound Y the same compound?

Answer 1

No, they are not the same compound. To show this, you need to convert the masses into moles (divide each amount by the molar mass).

Compound X has (15/1 =) 15 moles of H and (120/16 =) 7.5 moles of O. So this compound has twice as many atoms of H as O, like water (H2O).

Compound Y has (2/1 =) 2 moles of H and (32/16 =) 2 moles of O. So this compound has the same number of atoms of H as O, like hydrogen peroxide (H2O2).