11.18 (1)

11.18 (1) - T = P P . Using this formula we can solve for...

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Key: 18. How many grams of nitrogen are present in a sample if you know the partial pressures to be 0.7 atm nitrogen, 0.6 atm oxygen, and 1.2 atm hydrogen and the total number of moles in the gas is 1.8? a. < 1 g b. 5 g c. 14 g d. 7 g e. 10 g f. None of the above This problem asks you to figure out the mass of a gas when you are given information about its partial pressure. The ideal gas equation tells us that the pressure of the gas and the number of moles of molecules are directly related. And you also know that if you multiply the total gas pressure in a mixture by the mole fraction(X) of gas, you will get the partial pressure(P P ) of that gas. In other words, XP
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Unformatted text preview: T = P P . Using this formula we can solve for the mole fraction of a substance. Since we are given the total moles, this will provide us with the # of moles of that substance (mole fraction = moles of substance/total moles). After doing that, we can determine its mass. Below are the calculations: XP T = P P X(2.5atm) = 0.7atm *note: 2.5 atm is the total pressure and is the sum of the partial pressures Therefore, X = 0.28 Moles nitrogen/total moles = 0.28 Moles nitrogen/1.8mol = 0.28 Therefore, Moles nitrogen =0.5mol and from the moles of nitrogen, we can calculate the grams of nitrogen thus: 0.5 mol N 2 28g N 2 = 14 g N 2 1 mole N 2...
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This document was uploaded on 11/04/2011 for the course CHEM 106 at BYU.

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