PHYSICAL CHEMISTRY

PHASE DIAGRAM

Phase diagram

2 components

liquid - liquid

Experiment : to determine the graphs of phenol composition-temperature and the critical solution temperatures

[phenol] (%)

8 11 20 50 63 70 80

Phenol (mL)

4 5.5 10 25 31.5 35 40

Water (mL)

46 44.5 40 25 18.5 15 10

Results :

Phase diagram

2 components

liquid - vapor

If the interactions between A and B stabilise the liquid phase then the vapour pressure will be depressed below its ideal value and the boiling temperature raised.

Many liquid mixtures deviate from the ideal behaviourpredicted by Raoult's law. Ideal-dilute solutions are those for which the solvent obeys Raoult'slaw and the solute Henry's law.

Ideal solution

In a fractional distillation, the boiling and condensation cycle is repeated to get a pure substance. This technique is used to separate volatile liquids.

The vapor is collected and condensed in a simple distillation. This technique is used to separate a volatile liquid from a non-volatile solute or solid.

Distillation

distillate

condensation

azeotrope

Non ideal solution

Azeotrope:2 different types: a high-boiling azeotropea low-boiling azeotrope

is a particular mixture (two or more miscible liquids) which does not change the composition during the distillation

In a high-boiling azeotrope if a maximum occurs in the phase diagram, the liquid is stabilized due to favorable interactions between A and B molecules

the liquid is destabilized due to unfavorable interactions between A and B molecule

a low-boiling azeotrope

Phase diagram

2 components

liquid – liquid &

Liquid - vapor

X benz 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

PT 64 78 94 109 122 136 148 158 168 178 186

Problems :

1. Jika sebanyak 10 g A dan 50 g B dicampurkan pada suhu 25C. Keduanya hanya bercampur sebagian dan membentuk dua fasa. Jika % berat A dalam fasa I adalah 5%, dan dalam fasa II adalah 60%, hitung massa A dan B dalam dua fasa yang berada dalamkesetimbangan

2. Sistem benzena-toluena membentuk campuran dan tekanan total campuran tersebut merupakan fungsi dari komposisi sebagaimanayg diperlihatkan dalam tabel berikut.Buatlah diagram fasa P vs x untuk sistem tersebut ! Apakah sistem tersebut merupakan larutan ideal atau membentukazeotrop ?jika larutan awal memiliki x benzena = 0,4 pada suhu berapasebanyak ¾ bagian teruapkan ?