Lecture 2 with ink

Lecture 2 with ink - Lecture 2 Have a calculator handy...

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Lecture 2 Have a calculator handy!
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Boiling Point and Vapor Pressure Experiment 2 Review of Acid/Base Chemistry Extraction Techniques Drying Organic Liquids Recrystallization Experiment 3
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Let’s do an experiment http://viscog.beckman.uiuc.edu/flashmovie/15.php Points to this video Results can vary depending upon preconceived expectations Phenomenon experienced in class is called “attention blindness”
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Properties of solutions that depend upon the number of particles, not the mass of the particles. Freezing (Melting) point depression Freezing Point total = Freezing Point solvent Δ T f Boiling point elevation Boiling Point total = Boiling Point solvent + Δ T b Osmotic Pressure Vapor Pressure
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Liquid Vapor Vapor Pressure: pressure a liquid exerts on environment Boiling Point: when vapor pressure equals atmospheric pressure
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What chemical features influence boiling point? Intermolecular Forces Hydrogen Bonding VdW Forces Size of molecule (more surface area = more intermolecular forces
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Mohrig, page 128
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Rault’s Law ( P = P°X) P = partial vapor pressure P° = vapor pressure of pure substance X = mol fraction of pure substance in solution X A = mol A / total number of moles solution
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Question: What is the partial pressure of ethanol (P°=45.00kPa, FW=46.07g/mol) if 3.00 grams of it is mixed with 3.00 grams of something unknown (FW=32.04)?
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But doesn’t that unknown substance also have a partial pressure that contributes? P total =P A + P B (Sum of the partial pressures) Question: Assuming the unknown is methanol (P°=81.00kPa) what is the total vapor pressure above the solution?
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Let’s say we have an equal number of moles of ethanol and methanol in solution. What is the fraction of ethanol in the vapor? What we know:
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This note was uploaded on 04/09/2010 for the course CHEM 6a taught by Professor Pettus during the Winter '07 term at UCSB.

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Lecture 2 with ink - Lecture 2 Have a calculator handy...

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