Factors affecting adsorption: Pressure of Gas
In the forward direction, during adsorption, volume decreases since gases are adsorbed to the surface. Hence applying Le-Chatelier principle, we can predict effect of pressure. At high pressure, the system has a tendency to decrease volume and shifts towards forward direction, ie , more adsorption take place. Now we can conclude that extent of adsorption (x/m) increases with increase in pressure. Where x= number of the moles of gas adsorbed and m = mass of adsorbent, at equilibrium. Variation of x/m with pressure can be experimentally studied and can be plotted as a graph at constant temperature. Such graphs obtained by plotting (x/m) against (p) at constant temperature are called, adsorption isotherm.