Surface Chemistry
Surface chemistry is the study of phenomena occurring on the surfaces of substances. It has a wide range of applications, both in industries and everyday life. In simpler terms, surface chemistry is concerned with any type of surface phenomenon.
Table of Contents
Applications of Surface Chemistry
Role of Adsorption in Surface Chemistry
Effects of Pressure and Temperature on Adsorption
Emulsions in Surface Chemistry
Surface Chemistry is the branch of chemistry that studies the chemical and physical phenomena that occur at the interface of two phases, including solid-liquid interfaces, solid-gas interfaces, solid-vacuum interfaces, and liquid-gas interfaces.
Surface chemistry is the study of chemical phenomena that occur at the interface of two surfaces, such as:
- Solid-liquid
- Solid-gas
- Solid-vacuum
- Liquid-gas
Applications of surface chemistry, known as surface engineering, involve various phenomena taking place on the surface of substances, such as:
Applications of Surface Chemistry
In a broader view, surface chemistry focuses on the interaction between the surfaces of two systems. This concept is demonstrated in phenomena such as:
Surface Chemistry plays a major role in many chemical processes, including:
Enzymatic reactions located at the biological interfaces in cell walls and membranes are of great importance.
In the electronics industry, microchips found in computers typically have surfaces and interfaces that utilize them.
In automobile exhausts, heterogeneous catalysts are found in the catalytic converter to clean emissions.
Role of Adsorption in Surface Chemistry
Adsorption is the accumulation of species on the surface of a substance due to intermolecular forces. For example, gases such as H2, O2, and N2 can adsorb onto the surface of activated charcoal.
Learn More About the Difference Between Adsorption and Absorption Here
Enthalpy of Adsorption: The amount of heat energy released when a single mole of gas is adsorbed onto the surface area of one unit of an adsorbent is referred to as the enthalpy of adsorption.
Types of Adsorption
Adsorption in surface chemistry is classified into two types due to the force of interaction between adsorbate and adsorbent.
Physisorption or Physical Adsorption
There is a weak van der Waals force between an adsorbate and an adsorbent.
Characteristics:
Nature of Forces: Weak Van der Waals Forces
- Specificity: It is not specific in nature.
Reversibility: The process is reversible
Layer: It is a multi-layered process.
Enthalpy of Adsorption: Low enthalpy of adsorption (20 - 40 KJ/mole)
The Energy of Activation: Very Low
Desorption: Very Easy
Factors Affecting Adsorption:
- Surface Area of Adsorbent
- Nature of Adsorbate
- Pressure
- Temperature
Chemisorption or Chemical Adsorption
It is due to strong chemical forces between adsorbate and adsorbent.
Characteristics:
Nature of Forces: Strong Chemical Forces
Specificity: Highly specific nature
Reversibility: It is irreversible
Layer: It is a single-layered process.
Enthalpy of Adsorption: High enthalpy of adsorption (40 - 400 KJ/mole)
The Energy of Activation: Very High
Desorption: Very Difficult
Factors Affecting Adsorption:
- Surface Area of Adsorbent
- Nature of Adsorbate
- Temperature
The Impact of Pressure and Temperature on Adsorption
The Influence of Pressure on Gas Adsorption on a Solid
The pressure of the gas is proportional to the fraction of gas adsorbed. As the pressure increases, adsorption increases until it reaches a maximum and becomes constant.
Effect of Temperature on Adsorption of Gases on Solid
The adsorption of gases on solid surfaces is always an exothermic reaction.
The Lechatlier Principle states that as the temperature increases, the amount of gas adsorbed through physical adsorption decreases.
As the temperature increases, chemisorption also increases until it reaches its maximum, after which it starts to decrease.
The curve obtained by plotting the fraction of gas adsorbed against the temperature at a constant pressure is known as an Adsorption Isobar.
Surface Chemistry: Adsorption Isotherms
Freundlich Adsorption Isotherm
x^m = K[P^(1/n)]
The mass of adsorbate (x) is in relation to the mass of adsorbent.
log K/m = (log P + log K)/n
It does not apply to the adsorption of gases on solids at a higher pressure.
Langmuir Adsorption Isotherm
The layer of gas adsorbed on the solid adsorbent is one molecule thick.
The adsorbent has a uniform adsorbed layer.
There is no interaction between adjacent adsorbed molecules.
Emulsions in Surface Chemistry
Emulsions are colloidal solutions in which both the dispersed phase and the dispersion medium are liquids.
Answer: On the basis of dispersion medium, emulsions in surface chemistry are classified into two types: Paints, Dyes, Milk, and Vanishing Cream.
Oil in Water Emulsions
In this, water is dispersed with oil or fat droplets. Example: Milk.
Water and Oil Emulsions
In this, oil is dispersed with water droplets. Example: Vanishing cream.
Emulsions are unstable, so to increase their stability, a substance called an emulsifier is added. For example, milk contains a natural emulsion of casein.
Uses of Emulsions
These are used in syrups
Paints
Toothpaste
Digestion of Fats
Pigment and Dye
Chemical Kinetics and Surface Chemistry
Surface Chemistry: Top 10 Most Important Questions for JEE Main
Revision Concepts and Questions in Surface Chemistry
Frequently Asked Questions on Surface Chemistry
Surface chemistry is the study of chemical processes that occur at the interface of two phases, including solid/liquid, liquid/gas and solid/gas interfaces.
The enthalpy of adsorption in physisorption is a phenomenon studied in surface chemistry.
The enthalpy of adsorption in chemisorption is typically higher than 20-40 KJ/mol.
The enthalpy of adsorption in chemisorption is 40-400 KJ/mol.
What is meant by adsorbate?
An adsorbent is a material that adsorbs (or binds) molecules to its surface. It can be a solid, liquid, or gas, and is typically porous in order to maximize the surface area available for adsorption.
The compound that adsorbs the adsorbate on its surface is called an adsorbent.
