Surface Chemistry 12th Class
Surface Chemistry 12th Class: The branch of chemistry in which the surface properties of solids are studied calls surface chemistry.
Adsorption
When any other surface or substance, phase comes in contact with the surface of a solid, then that surface attracts its particles like its ions, atom and allows it to remain on the surface, call adsorption.
The substance that gets deposited on the surface calls adsorbent and the surface on which the substance settles call adsorbent.
Difference Between Adsorption and Absorption
Adsorption occurs only on the surface whereas absorption occurs throughout the object.
| Absorption | Adsorption |
| 1. Absorption is the state in which an atomic ion or molecule is absorbed by another substance (usually in a liquid or solid-state). | 1. Adsorption is the condition in which a gas, a liquid, or a dissolved solid, sticks to another substance that normally remains in the solid or liquid state. |
| 2. Absorption is a phenomenon that occurs in excess. Adsorption is a surface phenomenon. | 2. Absorption is a phenomenon that occurs in small quantities and is a phenomenon on the surface. |
| Adsorption is a surface phenomenon. | 3. Adsorption is very rapid in the beginning but its rate gradually decreases after reaching equilibrium. |
| 4. It is a gross phenomenon i.e. it occurs in the whole of the matter. | 5. It is a surface phenomenon i.e. it occurs only at the surface of the adsorbent. |
| 5. There is no significant heat change in this. | 5. This is an exothermic process. |
| 6. The substance that is absorbed is evenly distributed over the entire internal area of | 6. In this the substance is absorbed in the surface i.e. the concentration of the adsorbed substance is high at the surface. |
Example: Suppose there is a pillow of a sponge, you put it in water, then what will happen that the pillow will absorb all the water, which is calls absorption.
When a metal is immersed in water, then water comes on its surface, it will be adsorbed.
Catalysis
When the rate of a chemical reaction becomes fast or slow, it calls a catalyst.
Catalyst
Such a substance that increases or slows down the rate of a chemical reaction calls a catalyst. These are of two types:
- positive catalyst
- negative catalyst
In most reactions, the catalyst speeds up the reaction. Such catalysts, call positive catalysts, But there are some such catalysts that slow down the rate of the chemical reaction. Such catalysts call negative catalysts.
Homogeneous Catalysis
When the catalyst cause by a catalyst that is in the same phase as the reactant, such a catalyst calls homogeneous catalysis.
As the reactant is a liquid and the catalyst is also a liquid or the reactant is a gas and the catalyst is also a gas, then it calls homogeneous catalysis.
Heterogeneous Catalysis
When the catalysis occurs by a catalyst is not in the reactant phase of the chemical reaction, such as the reactant is a gas and the catalyst liquid, then heterogeneous catalysis.
Colloids
Thomas Graham did these experiments in 1861 and explained about colloids.
Such a state in which the substances do not diffuse into the animal membrane and can pass through the filter paper, calls colloid state. Their particles have a size of 1 to 1000 nm.
Colloidal Solution
A mixture having the property between homogeneous and heterogeneous mixtures whose particles are evenly dispersed in the solution, calls a colloidal solution.
