Temperature and Pressure Effects on Surfaces

The assumptions and simplifications of the Langmuir isotherm in the previous section lead directly to expressions for the pressure dependence of the surface coverage. In the case of a simple, reversible molecular adsorption process, the expression is, as shown in (13.18), 

Typical relationship between the surface coverage and the pressure of an adsorbed gas. 

At a given pressure, the extent of surface coverage is determined by the value of which in turn is dependent on both the temperature and the enthalpy of adsorption. The magnitude of the adsorption enthalpy is directly proportional to the strength of binding of the adsorbate to the surface. The value of can be increased by a reduction in the system 

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