MCAT General Chemistry Question 132: Answer and Explanation

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Question: 132

12. At sea level and 25°C, the solubility of oxygen gas in water is 1.25 × 10-3 M. In Denver, a city in the United States that lies high above sea level, the atmospheric pressure is 0.800 atm. What is the solubility of oxygen in water in Denver?

  • A. 1.00 × 10-3 M
  • B. 1.05 × 10-3 M
  • C. 1.50 × 10-3 M
  • D. 2.56 × 10-3 M

Correct Answer: A

Explanation:

The solubility of gases in liquids is directly proportional to the atmospheric pressure. This is called Henry's law, and is discussed in Chapter 8 of MCAT General Chemistry Review. Even without the formula, we know there is a direct proportionality between partial pressure and solubility. Because 0.800 atm is 80% of the pressure at sea level (1 atm), oxygen's solubility will be 80% of 1.25 × 10-3, which is 1.00 × 10-3 M.

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