MCAT General Chemistry Question 50: Answer and Explanation

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Question: 50

5. In which of the following compounds is the percent composition of carbon by mass closest to 62 percent?

  • A. Acetone
  • B. Ethanol
  • C. C3H8
  • D. Methanol

Correct Answer: A

Explanation:

The percent composition by mass of any given element within a molecule is equal to the mass of that element in the molecule divided by the molar mass of the compound, times 100%. In this case, acetone, C3H6O, has

Choice (B), ethanol, is

Choice (C), propane, is

Finally, choice (D), methanol, is

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