# 11.7 - XP T = P P Mole fraction(X = moles of...

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Key: 7. (Try this without a calculator) A bottle contains 2 g of helium, 10 g of neon, and 40 g of argon gases. The total gas pressure in the bottle is 600 torr. The partial pressures of the 3 gases (in mm Hg) are, in order a. 600,600,600 b. 600,300, 300 c. 300,300,600 d. 150,300,300 e. 150,150,300 f. 150,150,150 g. none of these We are given the total gas pressure, and the mass of three gases and asked to find partial pressures(P p ) of each. The ideal gas equation tells us that the pressure of the gas and the number of moles of molecules are directly related. This means that if you multiply the total gas pressure by the mole fraction(X) of gas, you will get the partial pressure of that gas. In other words,
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Unformatted text preview: XP T = P P Mole fraction(X) = moles of substance/total moles. To figure out the mole fraction, we need to figure out the number of moles of each gas. This is a simple conversion of grams to moles as shown below: 2g He│1mol He = 0.5 mol He │ 4g He 10g Ne│1mol Ne = 0.5mol Ne │ 20g Ne 40g Ar│1mol Ar = 1mol Ar │ 40 g Ar There are 2 total moles of gas which means that the mole fraction of He = 0.25, the mole fraction of Ne = 0.25, and the mole fraction of Ar = 0.5. Using XP T = P P : P P He: (0.25)(600torr) = 150torr P P Ne: (0.25)(600torr) = 150torr P P Ar: (0.50)(600torr) = 300torr...
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