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5.4 Phase diagrams of binary systems. Predict by phase law:. C=2, F=2- Φ +2=4- Φ. Φ min =1, F max =3. T, P, x. Three dimentional diagram. Intercepting plane graph---two dimentional diagrams. T, P, x ----- (T, x) p , (P, x) T or (T, P) x. Contents. Liquid-liquid Miscible
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5.4 Phase diagrams of binary systems Predict by phase law: C=2, F=2-Φ+2=4-Φ Φmin=1, Fmax=3 T, P, x Three dimentional diagram Intercepting plane graph---two dimentional diagrams T, P, x ----- (T, x)p , (P, x)T or (T, P)x
Contents • Liquid-liquid • Miscible • Partly-miscible • Immiscible • Liquid-solid • Water-salt • Solid-solid
5.4.1 Phase diagram of miscible binary systems 5.4.1.1 Ideal mixed systems: Two components both follow Raoult’s Law. ( )T, P-x, A+B
Liquid P Vapour xA ( )T, P-x-y liquid Liquid/ Vapour Φ=2 F=2-2+1=1(P) A is more volatile than B B is more volatile than A
T2 T3 x1 T1 x2 x3 x2 x3 x4 TB* The composition variation in the distillation process TA* d T3 d’ c T2c’ T b T1 b’ a a’ x4 x3 x2 x1 A B A How would it be in an closed system?
Relating P-x and T-x phase diagram Getting T-x phase diagram from P-x P-x,liquid(upper line)- gas(lower line) T-x,gas(upper line)-liquid(lower line)
5.4.1.2 The Lever rule C, total amount of the systems DE(tie line) isothermal
Phase equilibrium variation at constant temperature ---the level rule
T T1 T T2 5.4.1.3 The principle of distillation Simple distillation Separate a volatile liquid from a non-volatile solute or solid
Fractional distillation Theoretical plates: the number of effective vaporization and condensation steps that are required to achieve a condensate of given composition from a given distillate
P-x and T-x phase diagrams of non-ideal miscible binary systems
Azeotropes Low-boiling azeotrope
Low-boiling azeotrope 351.28K,95.57
High boiling azeotropes 381.65 K HCl 20.24 The maximum azeotropic point
Homework • Y: P161 17, 18 • A: P215 8.5(a), 8.6(a) • Preview: • Y: 5.5,5.6, 5.7 • A:8.5, 8.6