Bihar Board - Class 12 Chemistry - Chapter 5: Surface Chemistry Handwritten Notes

Surface chemistry is the branch of chemistry that deals with the study of the properties and reactions that occur at the surface of materials. It focuses on the interaction between the surface and the surrounding environment, including gases, liquids, and solids. Surface chemistry plays a crucial role in various fields, including catalysis, adsorption, and corrosion, and is essential for many industrial applications.

Key Points:

Adsorption:

Adsorption is the accumulation of molecules or ions at the surface of a solid or liquid.

It differs from absorption, where molecules are taken up into the bulk of the material.

Adsorption can be of two types:

• Physisorption (Physical Adsorption): Weak van der Waals forces are involved.
• Chemisorption (Chemical Adsorption): Strong chemical bonds are formed between adsorbate and adsorbent.

Catalysis:

Catalysis is the process of increasing the rate of a chemical reaction by adding a substance (catalyst) that is not consumed in the reaction.

There are two types of catalysis:

• Heterogeneous Catalysis: The catalyst is in a different phase than the reactants (e.g., solid catalyst and gaseous reactants).
• Homogeneous Catalysis: The catalyst and the reactants are in the same phase (e.g., both are in solution).

Examples include the use of platinum in catalytic converters and enzymes in biological reactions.

Surface Area:

The rate of adsorption and catalytic activity often increases with an increase in the surface area of the material.

Materials with large surface areas, such as activated charcoal or finely divided metals, are often used in adsorption and catalytic processes.

Colloids:

A colloid is a mixture in which one substance is dispersed in another, but the dispersed particles do not settle down.

Colloidal particles are typically between 1 nm and 1 µm in size and exhibit unique properties, such as the Tyndall effect, where light scatters through the colloidal particles.

Examples of colloids include milk, fog, and paint.

Emulsions:

Emulsions are colloidal systems in which liquids are dispersed in other liquids. Emulsifying agents, such as soaps, are used to stabilize emulsions.

Types of emulsions:

• Oil in Water (O/W): Example - Milk.
• Water in Oil (W/O): Example - Butter.

Langmuir Adsorption Isotherm:

The Langmuir adsorption isotherm describes the relationship between the amount of adsorbate on a surface and its pressure (or concentration).

It assumes that adsorption occurs at specific sites on the surface and that each site can hold only one molecule.

Bremmer's Adsorption Isotherm:

This is another model used to describe adsorption on surfaces, which is applicable to certain conditions, especially for gases adsorbed onto solids.

Corrosion:

Corrosion is the process of deterioration of metals due to chemical reactions with their environment, often leading to rust formation in iron.

Prevention methods include coating, galvanization, and using corrosion-resistant materials.

Conclusion:

Surface chemistry is an important field that helps us understand the behavior of substances at the interfaces between different phases, such as solid-liquid, solid-gas, and liquid-gas. The study of adsorption, catalysis, and colloids enables a wide range of industrial applications, from the design of catalysts for chemical reactions to the development of new materials and processes. Surface chemistry is also vital in addressing environmental concerns, such as corrosion and pollution, by providing insights into how materials interact with their surroundings.