How does the adsorption of N2 on charcoal with pressure vary at different constant temperatures?
An increase in pressure of the adsorbate gas increases the extent of adsorption at a particular temperature. At low temperature, the extent of adsorption increases very rapidly with pressure. Over a small range of pressure, the extent of adsorption is found to be directly proportional to the pressure. However, at higher pressures (closer to the saturation vapour pressure of the gas) the adsorption tends to achieve a limiting value.
It is experimentally observed that,
(i) at low pressures, the extent of adsorption varies linearly with pressure,
(ii) at high pressures, it becomes independent of pressure.
Now if x is the mass (in gram) of gas adsorbed on m gram of the adsorbent, then
In the intermediate range of pressure, therefore, x/m will depend on p raised to powers between 1 and 0 (i.e., a fraction). For a small range of pressure therefore, we can write:
Nitrogen gas adsorption on charcoal at low temperature is physisorption (upto 83 °C) and at high temperature behaves like chemisorption (at 773 K).
It is experimentally observed that,
(i) at low pressures, the extent of adsorption varies linearly with pressure,
(ii) at high pressures, it becomes independent of pressure.
Now if x is the mass (in gram) of gas adsorbed on m gram of the adsorbent, then
In the intermediate range of pressure, therefore, x/m will depend on p raised to powers between 1 and 0 (i.e., a fraction). For a small range of pressure therefore, we can write:
Nitrogen gas adsorption on charcoal at low temperature is physisorption (upto 83 °C) and at high temperature behaves like chemisorption (at 773 K).