Removal of adsorbate from the surface of the adsorbent is called desorption. That is, desorption is reverse of adsorption

Sorption is defined as the phenomenon in which one substance get attached to another. Sorbate is the substance that gets attached while the sorbent is the substance on which the sorbate gets attached to. An example of sorption is sponge dipped in water.

What are different types of adsorption? Give any four differences between characteristics of these different types.

There are two types of Adsorption – 1. Physical Adsorption or Physiosorption and 2. Chemical Adsorption or Chemisorption. Physical Adsorption Chemical adsorption 1. It arises because of vander Waals' forces. 1. It is caused by chemical bond formation. 2. It is not specific in nature. 2. It is highly specific in nature. 3. It is reversible in nature. 3. It is irreversible. 4. It depends on the nature of gas. Easily liquefiable gases are adsorbed readily. 4. . It also depends on the nature of gas.Gases which can react with the adsorbent show chemisorption. 5. Enthalpy of adsorption is low 20 - 40 kJ mo l - 1 5. Enthalpy of adsorption is high 80 - 240 kJ mol - 1 .

State Hardy - Schulze rule.

It has been observed that, generally greater the valence of the coagulating ion added, the greater is its power to cause coagulation. This is known as Hardy- schulze rule. In the coagulation of a negative sol, the coagulating power of cations is in the order A l 3 + > Ba 2 + > Na + .

Give two examples for heterogeneous catalysis.

Oxidation of sulphur dioxide Into sulphur trioxide In the presence of Pt . 2 SO 2 g → Pt s 2 SO 3 g The reactant Is In the gaseous state while the catalyst Pt Is In the solid state. Combination between dinitrogen and dihydrogen to form ammonia In the presence of finely divided Iron In Haber’s process. N 2 g + 3 H 2 g → Fe s 2 NH 3 g

E M B I B E

Intermediate Second Year Chemistry>Chapter 4 - Surface Chemistry>Questions>Q 4

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Distinguish between adsorption and absorption. Give one example of each.

Important Questions on Surface Chemistry

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Intermediate Second Year Chemistry>Chapter 4 - Surface Chemistry>Questions>Q 5

The moist air becomes dry in the presence of silica gel. Give reason for this.

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Intermediate Second Year Chemistry>Chapter 4 - Surface Chemistry>Questions>Q 6

Methylene blue solution when shaken with animal charcoal gives a colourless filtrate on filtration. Give the reason.

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Intermediate Second Year Chemistry>Chapter 4 - Surface Chemistry>Questions>Q 7

A small amount of silica gel and a small amount of anhydrous calcium chloride are placed separately in two corners of a vessel containing water vapour. What phenomena will occur?

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Intermediate Second Year Chemistry>Chapter 4 - Surface Chemistry>Questions>Q 8

What is desorption ?

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Intermediate Second Year Chemistry>Chapter 4 - Surface Chemistry>Questions>Q 9

What is sorption ?

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