# Vapor Liquid Equilibrium

Topics: Water, Gas, Vapor-liquid equilibrium Pages: 6 (1206 words) Published: April 25, 2013
Summary
The main objective of this experiment was to obtain some experimental measurement of Vapor Liquid Equilibrium for the Ethanol – Water system to verify the literature data. For this the Ethanol – Water system was heated to a certain temperature which is called the equilibrium temperature at atmospheric pressure and equilibrium temperature and compositions of vapor and liquid were measured. At the equilibrium temperature the samples of both vapor and liquid were taken in two different test-tube and the refractive index of both the samples were measured by a Refractometer. Then equilibrium compositions of vapor and liquid were measured from the calibration curve of refractive index vs molar composition. In our experiment equilibrium temperature were found 800C and the experimental compositions were found for vapor and liquid 50 and 15 respectively. This result was then compared with the literature value and the reasons behind the deviation were discussed in the discussion section.

Experimental Apparatus
* Pure ethanol
* Distilled water
* Spiral condenser
* Jacketed condenser
* Electric Heater with regulator
* Round Bottom flask
* Thermometer
* Distillate collector
* Refractometer

Experimental Setup

Figure 01: Apparatus for determination of liquid and vapor phase compositions of Ethanol Water system at equilibrium

Observed Data
Equilibrium Temperature = 800C
Refractive Index of feed solution = 1.357
Hence, from calibration curve of refractive index versus mole % of ethanol, Mole % of ethanol = 37.0%

Table 01: Observed Data for Vapor Liquid Equilibrium of Ethanol Water system Observation No.| Refractive Index|
| Liquid| Vapor|
01| 1.351| 1.362|
02| 1.3515| 1.3615|
03| 1.351| 1.3615|
04| 1.352| 1.3615|
05| 1.352| 1.3615|

Calculated Data

Table 02: Calculated data for equilibrium composition (% mole) of vapor and liquid Observation No.| Refractive Index| Composition (% mole)| | Liquid| Vapor| Liquid (x)| Vapor (y)|
01| 1.351| 1.362| 14| 56|
02| 1.3515| 1.3615| 14.5| 50|
03| 1.351| 1.3615| 14| 50|
04| 1.352| 1.3615| 15| 50|
05| 1.352| 1.3615| 15| 50|

Sample Calculation
Sample calculation for equilibrium data (Obs. no. 05)

At equilibrium temperature of 80oC and atmospheric pressure

* Experimental Composition (in % mole) of ethanol
* Liquid phase = 15
* Vapor phase = 50

* Theoretical Composition (in % mole) of ethanol
* From T-x-y diagram:
* Liquid phase = 48
* Vapor phase = 64.5
* From x-y diagram:
* Vapor phase = 50 (for experimental liquid phase = 15) * Liquid phase = 15 (for experimental vapor phase = 50) The experimental vapor and liquid phase compositions completely satisfy the equilibrium x-y graph.

Graphical Representation
The T-xy and x-y diagram for ethanol/water system is constructed from literature data in order to evaluate the theoretical composition of the two phases at equilibrium at the system temperature. Table 03: Literature data for ethanol/water system at equilibrium at 1 atmospheric pressure Temperature(oC)| Mole fraction of ethanol|

| Liquid phase| Vapor phase|
100| 0| 0|
95| 1.9| 17|
89| 7.21| 38.91|
86.7| 9.66| 43.75|
85.7| 12.38| 47.01|
84.1| 16.61| 50.89|
82.7| 23.37| 54.45|
82.3| 26.08| 55.8|
81.5| 32.73| 58.26|
80.7| 39.65| 61.22|
79.8| 50.7| 65.64|
79.7| 51.98| 65.99|
79.3| 57.32| 68.41|
78.74| 67.63| 73.85|
78.41| 74.72| 78.15|
78.15| 89.43| 89.43|
T-xy Diagram:

Figure 02: T-xy Diagram

At equilibrium temperature of 80oC and atmospheric pressure
Theoretical composition of ethanol
* vapor phase = 64.5
* liquid phase = 48

x-y Diagram:

Figure 03: x-y Diagram

At equilibrium temperature of 80oC and atmospheric pressure
Theoretical composition of ethanol
* vapor phase = 50...

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