Experiment 6 Simple and Fractional Distillation

Experiment 6 Simple and Fractional Distillation

VaVpaoprorPrPersessusruer (ek(PkaP)a)

Vapor Pressure (kPa)

VVaappororPrPersesussruerves vTsemTpemerapteurraetoufrWe oafteWr ater

250 250

250

200 200

200

115500

150

110000 100

Vapor Pressure vs Temperature of Water

5500 50

00 0

0 20 40 60 80 100 120 140

00 2020 4040Tem6p0era6t0ure8,0?C 80100 101020 112400 140 TemTpeemraptuerrea,tu?Cre, ?C

What is and what do the following measure?

vapor pressure The vapor pressure of a pure substance is the pressure exerted by the substance against the external pressure which is usually atmospheric pressure. Vapor pressure is a measure of the tendency of a condensed substance to escape the condensed phase.

boiling point: When the vapor pressure of a liquid substance reaches the external pressure, the substance is observed to boil.

normal boiling point: When the external pressure is atmospheric pressure, the temperature at which a pure substance boils is called the normal boiling point.

Hvap is the energy necessary to vaporize a mole of a pure substance

Avap

Bvap

HvapA

HvapB

Aliq

Bliq

f mixing liq A and liq B and mixing gas A and gas B results in no heat of mixing in both the liquid and gas phase, the system is considered to be ideal Then:

PA obs = APoA;

PB obs = BPoB

where PA obs; PB obs is the observed vapor pressure in the mixture;

A; B is the mole fraction of A, B, ... A = nA/ (nA +nB) B = nB/ (nA +nB)

and PoA; PoB are the vapor pressures of pure A and B

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