Question

Volatile liquids A and B are completely miscible and form ideal solutions in all proportions. The pure vapor pressures at 298K are PA* = 500. torr and PB* = 200. torr. Using Excel may reduce the amount of time required to complete the following requested effort. Calculate, at 0.1 mole fraction intervals (x_A = 0, 0.1, 0.2, . . . , 1) PA, PB, Ptotal, and y_A, which is the vapor phase mole fraction of A. (i)Present these calculations in a suitable table. (ii)Plot PA, PB and Ptotal, vs. x_A, and plot Ptotal, vs. y_A on the same mole fraction scale as x_A. All four plots should superimposed on the same axes as in the adjacent figure, but with labels for the lines/curves.

Answer 1

For x_A, we just need to write 0 to 1 with 0.1 interval.

For x_B, x_B = 1-x_A

For p_A = 500*x_A

p_B = 200*x_B

P_total = p_A + p_B

y_A = p_A/P_total

So, the excel table is:

xA	xB	pA	pB	Ptotal	yA
0	1	0	200	200	0
0.1	0.9	50	180	230	0.217391304
0.2	0.8	100	160	260	0.384615385
0.3	0.7	150	140	290	0.517241379
0.4	0.6	200	120	320	0.625
0.5	0.5	250	100	350	0.714285714
0.6	0.4	300	80	380	0.789473684
0.7	0.3	350	60	410	0.853658537
0.8	0.2	400	40	440	0.909090909
0.9	0.1	450	20	470	0.957446809
1	0	500	0	500	1

The plots are:

On overlapping the graph is: