Answer:
51.0% O
Explanation:
The formula for percent composition is:
mass of element
--------------------------- x 100%
mass of molecule
To find the percent composition of oxygen in the molecule, you need to (1) calculate the molar mass of both the molecule and oxygen, and then (2) calculate the percent composition of oxygen. The molar mass of oxygen is the atomic weight of oxygen multiplied by the amount of oxygen in the molecule (denoted by the subscript).
(Step 1)
Molar Mass (CaC₄H₄O₆):
40.078 g/mol + 4(12.01 g/mol) + 4(1.008 g/mol) + 6(16.00 g/mol)
Molar Mass (CaC₄H₄O₆): 188.15 g/mol
Molar Mass (O): 6(16.00 g/mol)
Molar Mass (O): 96.00 g/mol
(Step 2)
96.00 g/mol O
---------------------------------- = 0.510 x 100% = 51.0% O
188.15 g/mol CaC₄H₄O₆
