MCAT General Chemistry Question 214: Answer and Explanation

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Question: 214

6. Which of the following is true for a closed flask containing both 1 mole of ideal Gas X and 1 mole of real Gas Y?

  • A. The total energy of X is equal to the total energy of Y.
  • B. The average kinetic energy of X is equal to the average kinetic energy of Y.
  • C. The total volume available to the gases is the same as the total volume of the flask.
  • D. Gases X and Y are at different temperatures.

Correct Answer: B

Explanation:

B Temperature is a measure of average kinetic energy. If gases X and Y are in the same flask they must be at the same temperature, eliminating choice D and making choice B correct. The total energy of a gas is equal to its kinetic energy plus its potential energy. Since Gas Y is a real gas and experiences intermolecular forces, it has potential energy, whereas ideal Gas X does not. Therefore, choice A is eliminated. Real gas molecules occupy some volume in the container, whereas ideal gases have no molecular volume. Since the flask contains a real gas, the total volume available to the gases is slightly less than the total volume of the flask, eliminating choice C.

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