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Example 37.2 : The data given below are for the adsorption of nitrogen on alumina at 77.3 K. Show that they fit in a BET isotherm in the range of adsorption and find Vmono and hence surface area of alumina (m2/g). At 77.3 K, saturation pressure, P* = 733.59 torr. The volumes are corrected to STP and refer to 1g of alumina.
|
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P/ (torr)
|
37.67 |
74.20 |
114.54 |
142.0 |
185.34 |
| V (cm3/g: STP) |
23.14 |
28.1 |
33.1 |
36.35 |
41.49 |
|
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From the above data, we have |
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10  Z = 10(P/P*)
|
0.51 |
1.01 |
1.56 |
1.94 |
2.53 |
| x = 103Z/(1-Z) (V/cm3) |
2.32 |
3.99 |
5.58 |
6.62 |
8.16 |
|
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A plot of z/(1-z) against z will give a straight line with intercept z = 0 as equal to  and slope will be  |
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Intercept of the plot is 0.987 10-3 cm-3 where as slope = 2.88 10-2 cm-3 |
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Intercept = = 0.987 10-3 cm-3 = 9.87 10-4 cm-3 |
