Question

On the basis of enthalpy and adsorption isobars, how physical and chemisorption differ?
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Answer 1

Answer:

Physical adsorption is performed at low temperatures by a weak bonding force called van der Waals. The heat released from this adsorption does not exceed 5 kcal/mol. This adsorption increases with increased gas pressure and decreases with high temperature. The gas is more absorbent as it is easy to liquefy. Depending on the case, the gas can have a monolayer or multi-particle layer on the surface.

Chemical adsorption

It is a bond between the surface particles of a metal (or of any other substance with high surface energy), a substance of a maze and another substance (gas or liquid) in contact with it (an excess material). These bonds are almost as strong as conventional chemical bonds, much stronger than the van der Waals forces characteristic of physical adsorption. The heat released from this adsorption is about 50-100 kcal/mol, and chemically absorbed molecules are often replaced. For example, molecular hydrogen chemically adsorbs to surface Metallic in the form of hydrogen atoms. A practical example of chemical adsorption is the lubrication or lubrication of the metal moving parts of the machinery. Chemical adsorption requires solid objects with high surface energies such as nickel, silver, platinum and iron. Chemical adsorption plays a very important role in the interpretation of heterogeneous catalysis. It is worth mentioning that physical and chemical adsorption can occur simultaneously at the surface, especially at low temperatures. For example, carbon dioxide adsorption on SiO2-NiO surface.