[Humongous]

Hey, I'm struggling to plot a graph for Phase Equilibria.

My lab had the results of

Ln P (mm Hg)           T (C)       T (K)        1/T (K-1)

[/HR]         
3.867    -15   258.5           0.00387
3.661    -19   254.5           0.00393
3.469    -23   250.5           0.00399
3.285           -27   246.5           0.00406
3.049           -31   242.5           0.00412
2.839           -35   238.5           0.00419
2.588           -40   233.5           0.00428
2.407    -43   230.5           0.00434
2.208    -46   227.5           0.0044
1.988           -49   224.5           0.00445
1.668           -52   221.5      0.00451
1.526           -55   218.5           0.00458
[/HR]

I says to plot ln P against 1/T initially, then to draw the best straight line through the upper temperature points and another through the lower points. The triple point lies at the intersection of the two lines.

Upper   Lower
[/HR]
46.8     94.6
51.4   90.3
54.8   86.9
57.5   84.2
60.4   81.5
62.4   79.5
64.3   77.6
65.4   76.5
66.4   75.5
67.3   74.6
68.0   73.3
68.6   73.2

I don't know how to make the graph. Sorry for post like it is I dont know how to enter it as a table.

[Borek]

Hard to make much from your data, and no idea what the problem is. Have you tried simply to put the data points on the plot to see if there is a pattern??

[Humongous]

Hi thanks for the reply. I've tried doing as the report has said but the graph isn't showing as expected. There's no intersect.

The book says a plot of ln P agianst (1/T) consists of two lines intersecting at the triple point.
ln P
(mm Hg)

3.867
3.661
3.469
3.285
3.049
2.839
2.588
2.407
2.208
1.988
1.668
1.526

1/T (K-1)

0.00387
0.00393
0.00399
0.00406
0.00412
0.00419
0.00428
0.00434
0.0044
0.00445
0.00451
0.00458

[Borek]

Can you describe the experiment and the data? You have two lists of some kind of data (upper, lower), but only one list of data points (which don't fit neither of these lists). No idea what is what of what.

[Humongous]

Can you describe the experiment and the data? You have two lists of some kind of data (upper, lower), but only one list of data points (which don't fit neither of these lists). No idea what is what of what.

Aim: 
To apply the Clausius-Clapeyron equation to the liquid-vapour and solid-vapour equlibria of perfluorocyclobutane, and the calculation of the following quantities for perflurorocyclobutane from the results:
•   The molar enthalpies of vaporisation, sublimation, and fusion;
•   The temperature and pressure of the triple point;
•   The normal boiling point.


Results:

Manometer levels / mm Hg Upper ||    Manometer levels / mm Hg  Lower ||    P / mm Upper - lower
46.8   94.6   47.8
51.4   90.3   38.9
54.8   86.9   32.1
57.5   84.2   26.7
60.4   81.5   21.1
62.4   79.5   17.1
64.3   77.6   13.1
65.4   76.5   11.1
66.4   75.5   9.1
67.3   74.6   7.3
68.0   73.3   5.3
68.6   73.2   4.6

Second half of the table

ln P (mm Hg) ||   T (C) ||   T (K) ||   1/T (K-1)
3.867    -15   258.5   0.00387
3.661   -19   254.5   0.00393
3.469   -23   250.5   0.00399
3.285   -27   246.5   0.00406
3.049   -31   242.5   0.00412
2.839   -35   238.5   0.00419
2.588   -40   233.5   0.00428
2.407   -43   230.5   0.00434
2.208   -46   227.5   0.00440
1.988   -49   224.5   0.00445
1.668   -52   221.5   0.00451
1.526   -55   218.5   0.00458

Then it asks to plot ln P against 1/T which gives me a straight line graph. It asks to draw the best line through the upper temperature points (liquid vap) and another through the lower temp points. The triple point lies at the intersection of the two lines.

I cant seem to figure it out.

[Borek]

You have not described the experimental procedure so I still can only guess.

You should have two sets of data - one for the gas/liquid equilibrium, the other for solid/gas equilibrium. If you have only one set of data, you can't do more than you already did (draw one line).