BP Diagrams and Azeotropes

BP Diagrams and Azeotropes - (Temperature-composition...

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Some “dissolving” involves chemical reactions. .. Reaction of ester with base (KOH or NaOH) to form alcohol (e.g., glycerol) and fatty acid salt (“soap”). (triglyceride) Ammonia cleaning action: NH 3 + H 2 O NH 4 + + OH - Cleaning up grease with ammonia: Saponificaton Note surfactant character C-C-C-C-C-C-C-C-C-C-C-C-C-C-C O Just something of interest for you
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What we know about binary solutions of volatile substances Raoult’s Law of ideal solutions allow us to predict partial pressures (and total pressure) at a given temperature if we know P o Non-ideal solutions cause positive or negative deviation of what is predicted by Raoult’s Law We cannot predict when a solution will boil (i.e., at what temperature the total pressure is 1 atm) X A 0 1 Press P o A P o B P Tot P o B X A 0 1 P o A P Tot
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What we need is information on the boiling point (T b ) as a function of mole fraction (e.g., X A )... and… the composition of the vapor above the boiling liquid ? X A 0 1 T b
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Boiling point diagram
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Unformatted text preview: (Temperature-composition diagram) X A 1 T b ( o C) X A (vapor) X A (soln) Soln composition Vapor composition Consider a solution where X A = 0.75 Solution boils at 92 and vapor composition is 0.35 92 0.35 150 50 Vapor (distillate) getting richer in more volatile benzene, but pot getting richer in less volatile toluene A B C D D THE EXPERIMENT Fractional distillation 20 40 60 80 100 120 140 0.2 0.4 0.6 0.8 1 X A boiling temperature ( o C) Minimum boiling azeotrope Original composition of pot Composition of the distillate moves toward fixed composition Maximum boiling azeotrope Composition of the pot moves toward fixed composition Colligative properties (depends on number of particles , expressed as molality ) Boiling point elevation Freezing point depression Osmotic pressure...
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BP Diagrams and Azeotropes - (Temperature-composition...

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