What is the approximate percent-by-mass of oxygen in (molar mass = 60 g)?

Question

What is the approximate percent-by-mass of oxygen in (molar mass = 60 g)?

Answer 1

if the formula has 1 oxygen:

16g / 60 g (100) = 26.67%

your answer : 27% oxygen, as in either propanol C3H7OH

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if the formula has 2 oxygens:

32g / 60g (100) = 53.33

your answer is: 53% oxygen, as in acetic acid CH3CO2H

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if the formula has 3 oxygens:

48g / 60g (100) = 80

your answer is 80% oxygen, as in the carbonate ion (CO3)-2