Introduction to NCERT Exemplar Solutions for Class 12 Chemistry Chapter 5: Surface Chemistry
Surface Chemistry is a branch of Chemistry that deals with the study of phenomena occurring at the boundary between two phases, such as solid–gas, solid–liquid, or liquid–gas interfaces. Many important processes in industries, the environment, and even in biological systems depend on surface phenomena. The Class 12 NCERT Exemplar Solutions for this chapter guide students through conceptual as well as application-based problems, ensuring clarity on topics like adsorption, catalysis, and colloids.
Adsorption
The first section introduces adsorption, which is the accumulation of molecules of a substance on the surface of another. This is different from absorption, where molecules penetrate into the bulk. Adsorption is classified into physical adsorption (physisorption) and chemical adsorption (chemisorption). Physisorption involves weak van der Waals forces and is reversible, while chemisorption involves chemical bonding and is usually irreversible. Exemplar questions test a student’s understanding of differences between the two, factors affecting adsorption, and the practical applications of adsorption, such as in gas masks, heterogeneous catalysis, and purification processes.
Adsorption Isotherms
To study adsorption quantitatively, students learn about Freundlich adsorption isotherm, which gives an empirical relationship between the extent of adsorption and pressure. Exemplar problems provide practice in applying the mathematical form of the isotherm and interpreting adsorption data. This not only develops problem-solving skills but also helps in linking theoretical models to experimental results.
Catalysis
Another major section of surface chemistry is catalysis, where the speed of a reaction is altered by the presence of a catalyst without itself undergoing permanent change. Students learn about homogeneous catalysis, where reactants and catalyst are in the same phase, and heterogeneous catalysis, where they are in different phases. The adsorption theory of catalysis explains how reactants are adsorbed on the surface of catalysts, bonds are weakened, and products are desorbed. Exemplar problems highlight applications such as the Haber process for ammonia synthesis, the contact process for sulfuric acid manufacture, and catalytic converters used in vehicles to reduce pollution.
Enzyme Catalysis
Biological systems also rely heavily on catalysis. Enzymes, which are protein molecules, act as biocatalysts in living organisms. Their efficiency, specificity, and sensitivity to conditions like pH and temperature make them unique. Exemplar questions often ask students to explain the mechanism of enzyme action, which involves the formation of an enzyme–substrate complex. This section links chemistry with biology and helps students appreciate interdisciplinary applications.
Colloids
A major portion of this chapter deals with colloidal systems, which are mixtures where one substance is dispersed in another in the form of tiny particles. Based on the dispersion medium and dispersed phase, colloids are classified into sols, gels, emulsions, aerosols, and foams. The properties of colloids, such as the Tyndall effect, Brownian movement, and electrophoresis, are explained in detail. Exemplar questions give students opportunities to analyze why these properties occur and how they are utilized in practical applications.
Preparation and Purification of Colloids
Various methods, like condensation and dispersion, are discussed for preparing colloids. Techniques such as dialysis, centrifugation, and coagulation are used for purification. Exemplar solutions provide step-by-step answers to problems related to these processes, helping students understand how colloids are obtained and purified in laboratories as well as in industries. Also, solve questions of NCERT with the help of NCERT solutions for class 12 Chemistry.
Applications of Colloids
Colloids play a vital role in everyday life and industries. Examples include cleansing action of soaps and detergents, medicines, photography, and the manufacture of paints, rubber, and synthetic fibers. The NCERT Exemplar questions encourage students to relate theoretical concepts to real-world uses, making learning more meaningful.