Chapter 6 Part 2

Chapter 6 Part 2 - Homework set due next Tuesday Extra...

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• Homework set due next Tuesday Extra Credit Deadline #2: November 13 Chapter 6 Lecture Notes Part 1 posted on WebCT In the news today: Chinese-made “Aqua Dots” bead toys contain toxic drug (a simple chemical compound used in manufacturing) http://www.cnn.com/2007/US/11/08/toy.recall/in dex.html?iref=mpstoryview See also video
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The Mole From left: one mole of sugar, salt, carbon, copper; the balloon contains helium (He)
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The Mole
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The Mole Molar Volume of a Gas: One mole of any gas occupies a volume of 22.4 L at s tandard t emperature and p ressure (STP). STP is defined as 1 atmosphere (atm) of pressure and a temperature of 0 o C . • Mass of 22.4 L (at STP) of different gasses differ Gas densities are given in the units of g/L
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Calculate the density of (a) nitrogen gas and (b) methane (CH 4 ) gas, both at STP. Calculate the density of He at STP. Exercise 6.7A EXAMPLE 6.7 Density of a Gas at STP Solution a. The molar ass of N 2 gas is 28.0 g/mol. We multiply by the conversion factor 1 mol N 2 = 22.4 L, arranged to cancel units of moles . b. The molar mass of CH 4 gas is (1 x 12.0) g/mol + (4 x 1.01) g/mol = 16.0 g/mol. Again we use the conversion factor 1 mol CH 4 = 22.4 L. x = 1.25 g/L 28.0 g N 2 1 mol N 2 1 mol N 2 22.4 L N 2 x = 0.714 g/L 16.0 g CH 4 1 mol CH 4 1 mol CH 4 22.4 L CH 4 Estimate the density of air at STP (assume 78% N 2 and 22% O 2 ) and compare this value to the value of He you calculated in Exercise 6.7A. Exercise 6.7B
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The density of diethyl ether vapor is 3.30 g/L. Calculate the molar mass of diethyl ether. The density of an unknown gas at STP is 2.30 g/L. Calculate its molar mass. Exercise 6.8A EXAMPLE 6.8 Molar Mass from Gas Densities Solution This time we are given the density in g/L. We want molar mass, which has units of g/mol. Once again we have the factor 22.4 L = 1 mol diethyl ether. Clearly, we must cancel the unit of liters and obtain the unit of moles in the denominator.
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Chapter 6 Part 2 - Homework set due next Tuesday Extra...

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