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?

In order to determine if compounds X and Y are the same, the mole percentages of the elements present should be equal in both compounds.

For compound X

number of moles H = 15/ 1 =15 mol H
number of moles O = 120/ 16 = 7.5 mol O

total moles = 22.5 mol

mole percentages
% mole H = 67%
% mole O = 33%

For compound Y 

mole of H = 2 /1 = 2
mole of O = 32/16 = 2

total mole = 4 mole

mol %

% mol H = 50%
% mol O = 50%

there the two compounds are not the same.

The answer should be c.