Question

The following data were obtained for the adsorption of n-butane on a porous solid (catalyst).  

	Adsorbed amount in mmol/g
Pressure (kPa)	85 °C	150 °C
0.67	0.51	0.13
1.33	0.85	0.25
2.67	0.98	0.40
5.33	1.09	0.59
10.67	1.18	0.76
21.33	1.25	0.89
33.33	1.30	0.96

Calculate the area (in m²) occupied by a n-butane molecule at 150°C.

Answer 1

Let P = Pressure (kPa)

q = Adsorbed amount (mmol/g) (q data is only Taken for T=150 0C)

P (kPa)	q (mmol/g)	P/q (g.kPa/mmol)
0.67	0.13	5.153846
1.33	0.25	5.32
2.67	0.4	6.675
5.33	0.59	9.033898
10.67	0.76	14.03947
21.33	0.89	23.96629
33.33	0.96	34.71875

Langmuir Isotherm plot

where, y=P/q

x = P

from the plot, we can see that Langmuir isotherm fits the given data very well then,

Surface area covered by one molecule of n-Butane ()