Question

Question 2 of Question on Vapour pressure

(b) If a solution containing 35 mole % n-hexane is vaporized, what is the composition of the initial vapour formed? What is the boiling point of the solution?

Vapour pressure data for n-hexane and n-octane are given in the following table. Vapour Pressure (mmHg) n-Hexane n-Octane Temperature (°F) 155.7 760 121 175 1025 173 200 1480 278 225 2130 434 250 3000 654 258.2 3420 760 Fig. Q1 (a) Construct a T-xy plot for the system at 1atm (760 mmHg) pressure. Also, plot y versus x. Base the plots on the hexane. State any assumptions clearly. Graph paper is attached, but you can also use any relevant software package to illustrate the graph.

Answer 1

(b)

From the figure we can find the vapour composition and the boiling point of the solution.

The intersection from the vertical line from on the T-x curve will give us the boiling point and the horizontal extension and intersection on the T-y curve gives us the vapour composition.

r= 0.35

270 250 Tvs y 230 T 210 Tb=205.5 F 190 TVS X 170 150 0 0.1 0.2 0.3 0.4 0.5 X Y 0.6 0.7 0.8 0.9 1 X=0.35 y=0.74
So the vapour contains 74% Hexane and the boiling point of the given solution is
205,5°F