AP Chemistry : Ideal Gas Law

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #21 : Ideal Gas Law

A gas mixture at equilibrium held over water at  contains 2.0 moles of oxygen, 9.0 moles of nitrogen, and 1.0 moles of water vapor. What is the vapor pressure of water at , if the total pressure exerted by the gases is 780mmHg?

Possible Answers:

Correct answer:

Explanation:

The molar quantity of a gas is directly proportional to its partial pressure, so if we have a total of 12 moles of gas, and  of the gas sample is water vapor, then water vapor makes up  of the total pressure. Thus to get the partial vapor pressure of any of the substances, we multiply the total vapor pressure by the proportion of that gas.

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