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Using atomic masses C=12, H=1, O=16 g/mol, what percent by mass of O is in ethanol (C2H6O)?

A) 44.8%

B) 24.8%

C) 65.2%

D) 34.8%

Answer: D

Explanation: The formula mass is about 46 g/mol; O contributes 16 g per mole. Divide 16 by 46 and multiply by 100 to obtain about 34.8%.

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