Adsorption and Critical Temperature

In summary: This is because the VDW forces are stronger near the critical temperature, making it easier for the gas molecules to be adsorbed. Therefore, the activated charcoal will be able to adsorb more of these gases, with SO2 being the most easily adsorbed, followed by CH4 and then H2. In summary, higher critical temperature gases are more easily adsorbed due to stronger Van der Waals forces, and activated charcoal can adsorb more of these gases, with SO2 being the most readily adsorbed gas.
  • #1

Homework Statement

An extract form my textbook:
" In general, easily liquefiable gases( ie. with higher critical temperature) are readily adsorbed as van der walls forces are stronger near the critical temperature. Hence 1g of activated charcoal adsorbs more SO2( Tc=630K),than CH4 (Tc=190K) which is still more than 4.5 mL of H2(Tc=33K)."

Homework Equations

The Attempt at a Solution

I'm having trouble understanding what this means.
1) Are we talking about VDW forces between the adsorbate( the gas) and the adsorbant? If so how are they stronger near Tc?
2) Are these gases liquefied and then adsorbed? Is this the general situation for adsorbtion of all gases?
3) What is the conclusion I'm supposed to draw from all this?
Please do help.
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  • #2
1) Yes, you are talking about Van der Waals forces between the adsorbate (the gas) and the adsorbant. The VDW forces are stronger near the critical temperature because the molecules of the gas are closer together and therefore have stronger intermolecular interactions. 2) Yes, these gases are liquefied and then adsorbed. This is not necessarily the general situation for adsorption of all gases, as some gases can be adsorbed in their gaseous state.3) The conclusion you can draw from this is that gases with higher critical temperatures are more easily adsorbed than gases with lower critical temperatures.

1. What is adsorption?

Adsorption is the process by which molecules or particles from a gas, liquid, or dissolved solid adhere to a surface.

2. What is the difference between adsorption and absorption?

Adsorption is a surface phenomenon where molecules adhere to the surface of a solid or liquid, while absorption is a bulk phenomenon where molecules are taken up into the body of a solid or liquid.

3. What is the critical temperature of a substance?

The critical temperature of a substance is the temperature at which the liquid and gas phases of the substance can no longer be distinguished from each other. Above this temperature, the substance will exist only as a gas, regardless of the pressure.

4. How does adsorption change with temperature?

Adsorption generally decreases with increasing temperature, as the increased thermal energy of the molecules makes them less likely to adhere to a surface.

5. How is critical temperature related to adsorption?

The critical temperature of a substance can affect its adsorption properties, as above the critical temperature, the substance will exist only as a gas and therefore will not be able to adsorb onto a surface. This can impact the efficiency of adsorption processes in industries such as natural gas processing and refrigeration.

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