ch22---phase-equilibrium-II.ppt

5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 21Chapter 22Phase Equilibrium II:Two-Component Systems22.1 Two-Component System Mixture of Two Miscible Liquids22.2 Raoults Law for Ideal Solutions22.3 Deviation from Raoults Law Non-ideal Solutions22.4 Fractional Distillation22.5 Azeotropic Mixtures5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 22Mixture of Two Miscible Liquids2 miscible liquidsvapour phaseliquid phase22.1 Two-Component System Mixture of Two Miscible Liquids (SB p.258)5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 230%100%liquid A100%0%liquid BVapour pressureliquid compositionTotal vapour pressuree.g.liquid A(hexane)liquid B(heptane)22.1 Two-Component System Mixture of Two Miscible Liquids (SB p.258)Ideal Solutions5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 24PB0PA00%100%liquid A100%0%liquid BVapour pressureRaoults Law for Ideal SolutionsPA=v.p.of APB=v.p.of BPure APure B22.2 Raoults Law for Ideal Solutions (SB p.259)Partial pressure of A:PA=APAPartial pressure of B:PB=BPBPT=PA+PBRaoults Law5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 25Raoults Law states that the vapour pressure of a component in a mixture at a given temperature is directly proportional to its mole fraction in the liquid mixture,and is equal to the product of its mole fraction in the liquid mixture and the vapour pressure of the pure component at that temperature.Raoults Law22.2 Raoults Law for Ideal Solutions (SB p.259)Partial pressure of A:PA=APAPartial pressure of B:PB=BPB5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 2622.2 Raoults Law for Ideal Solutions (SB p.263)Ideal SolutionThe tendency of the molecules of A and B in the mixture to change from liquid phase to the vapour phase is almost equal to that in pure A and pure B.benzenemethylbenzenePropan-1-olPropan-2-olbromomethane iodomethane5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 27a is the liquid composition(A,B),b is the vapour composition(yA,yB).aPT ,bIn this example,which is the more volatile liquid(A or B)?22.2 Raoults Law for Ideal Solutions (SB p.262)5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 28A vapour composition line is added to the graph.aT1 ,bCan you read from the graph that A is the more volatile liquid?22.2 Raoults Law for Ideal Solutions (SB p.262)5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 29(a max.in v.p.graph)(a min.in b.p.graph)22.3 Deviation from Raoults Law Non-ideal solutions(SB p.264)Positive Deviation from Raoults Law5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 210cyclohexaneethanol22.3 Deviation from Raoults Law Non-ideal solutions(SB p.266)Solutions having positive deviationThe average intermolecular attraction between a molecule of A and a molecule of B is weaker than the average of that between two A molecules in pure A and that between two B molecules in pure B.5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 211The introduction of cyclohexane inhibits the formation of some of the hydrogen bonds.This leads to+ve deviation(a v.p.greaterthan that predicted by Raoults Law).22.3 Deviation from Raoults Law Non-ideal solutions(SB p.266)5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 212(a min.in v.p.graph)(a max.in b.p.graph)22.3 Deviation from Raoults Law Non-ideal solutions(SB p.267)Negative Deviation from Raoults Law5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 213propanonetrichloromethane22.3 Deviation from Raoults Law Non-ideal solutions(SB p.268)Solutions having negative deviationThe average intermolecular attraction between a molecule of A and a molecule of B is stronger than the average of that between two A molecules in pure A and that between two B molecules in pure B.5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 214Hydrogen bond cannot be formed in individual liquids but in a mixture of trichloromethane and propanone.This leads to-ve deviation(a v.p.lower than that predicted by the Raoults Law).22.3 Deviation from Raoults Law Non-ideal solutions(SB p.268)5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 215Starting with a liquid mixture of composition x,after a series of consecutive distillations,BPure A is obtained in the final distillate.Pure B is obtained in the final residue.A is the more volatile.22.4 Fractional Distillation(SB p.269)Boiling point-composition curve5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 216The laboratory set-up of fractional distillation22.4 Fractional Distillation(SB p.270)An ideal solution can be separated completely by fractional distillation.5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 21722.4 Fractional Distillation(SB p.271)A fractionating tower5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 218If original conc of liquid mixture is M(azeotropic mixture),vapour has thesame composition as liquid throughout.If original conc of liquid mixture is to the left of M(say x):fractional distillation leads to pure B in the vapour&an azeotropic mixture in the residue.If original conc of liquid mixture is to the right of M(say w):fractional distillation leads to pure A in the vapour&an azeotropic mixture in the residue.22.5 Azeotropic Mixtures(SB p.272)Negative Deviation from Raoults Law5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 219If original conc of liquid mixture is M(azeotropic mixture),vapour has thesame composition as liquid throughout.If original conc of liquid mixture is to the left of M(say x):fractional distillation leads to an azeotropic mixture in the vapour&pure liquid B in the residue.If original conc of liquid mixture is to the right of M(say w):fractional distillation leads to an azeotropic mixture in the vapour&pure liquid A in the residue.22.5 Azeotropic Mixtures(SB p.272)Positive Deviation from Raoults Law5/21/2024H+H+H+OH-OH-OH-New Way Chemistry for Hong Kong A-Level Book 220