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Chemical Engineering
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Exercises for Lecture 1
Dr Colin HareChemical Engineering
School of Process, Environmental and Materials EngineeringUniversity of Leeds
Tel. 32407e-mail [email protected]
Example 1 Phase Diagram & Equilibrium Curve
Use Raoult's Law to calculate the vapour and liquid compositions in equilibrium (in mole fractions, y and x) for the benzene-toluene system using vapour pressure data measure at a pressure of 101.32 kPa as shown in the table below :
Solution to Example 1 Write Raoult's Law for a binary mixture of A and B
pA = Pvp,A xA ; pB = Pvp,B xB = Pvp,B (1 - xA) The total pressure, PT = pA + pB Replacing for the partial pressures and re-arrange, we have:
As Pvp,A xA = yA PT, then
The Vapour-Liquid Equilibrium data can be calculated at each temperature by substituting for total pressure (101.32 kPa) and the appropriate vapour pressures. For example, at 85.0 oC,
Solution to Example 1
One has the following Table:
Solution to Example 1
One has the following Table:
T (oC) xB yB xT yT KB KT αBT
80.1 1 1 0 0 1 - -
85.0 0.78 0.9 0.22 0.1 1.154 0.454 2.542
90.0 0.581 0.777 0.419 0.223 1.337 0.532 2.513
95.0 0.411 0.632 0.589 0.368 1.538 0.625 2.461
100.0 0.258 0.456 0.742 0.544 1.767 0.733 2.411
105.0 0.130 0.261 0.870 0.739 2.008 0.849 2.365
110.6 0 0 1 1 - 1 -
Solution to Example 1 (C) One can also plot the T-X-Y and X-Y diagrams