NCERT Solutions Class 12 Chemistry Chapter 5

NCERT Solutions Class 12 Chemistry Chapter 5 Surface Chemistry

NCERT Solutions Class 12 Chemistry Chapter 5 Surface Chemistry is summarised by experts at Extramarks to benefit the students studying in class 12. Students preparing for CBSE Class 12 examination must consider NCERT Solutions to understand the chapter. The Surface Chemistry chapter shows the role of adsorption, kinds of adsorption, pressure effects, and temperature effects on the surface and explains a few topics. The study material provided by Extramarks for NCERT Solutions Class 12 Chemistry Chapter 5 will be an excellent help for CBSE students.

Key Topics Covered In NCERT Solutions Class 12 Chemistry Chapter 5 Surface Chemistry

The table below details the class 12 chemistry ch 5 NCERT solutions. Let’s have an overview of the constituent topics of this chapter.

Students may click on the topics to access  Chapter 5 Chemistry Class 12 NCERT solutions for the respective exercise. A brief of the various topics that come under the NCERT Solutions Class 12 Chemistry Chapter 5 is given below. 

Surface Chemistry works with the chemical reactions at the surface or interface. There is a broad range of practical applications which involves surface chemistry. From the production of high vacuum to the manufacturing of Gas Masks, surface chemistry principles are used widely. It is also used to understand the catalyst reactions, Tyndall effect and Brownian movement, used for various applications. 

5.1 Adsorption

The accumulation of attracting and keeping the molecule of a substance on the surface of a solid is called adsorption. This results in an enhanced concentration on the surface than in bulk. The adsorption of a gas on a solid material depends on the following factors: surface area of the solid, temperature of the gas, nature of the gas, the pressure of the gas, and nature of the solid. 

Adsorption is the first exercise under NCERT Solutions Class 12 Chemistry Chapter 5 and includes

• Adsorbate: It is the substance that is being adsorbed on the surface of another substance.
• Adsorbent: It is the substance present in bulk, on the surface of which adsorption takes place.
• Desorption: In this process of removing an adsorbed substance from a surface on which it is adsorbed. 
• Adsorption: As per NCERT Solutions Class 12 Chemistry Chapter 5, absorption is the phenomenon in which a substance is uniformly distributed throughout the bulk of the solid. The concentration is the same throughout the bulk of the solid.
• Sorption: When adsorption and absorption take place at the same time, it is known as sorption.
• Enthalpy or heat of adsorption: when adsorption happens with the release of energy, that is exothermic in nature. The enthalpy change for the adsorption of a mole of an adsorbate on the surface of the adsorbent is known as enthalpy.

Types of adsorption: Types of adsorption mentioned in NCERT Solutions Class 12 Chemistry Chapter 5 are as under. 

• Physical adsorption: When adsorbate is held on a surface of the adsorbent by weak van der Waals’ forces, the adsorption is known as physical adsorption or physisorption. It is non-specific and reversible. The amount of gas depends upon nature. The scope of adsorption increases with an increase in surface area, like porous and finely divided metals are suitable adsorbents. 
• Chemical adsorption or chemisorption: If the forces holding the adsorbate are as strong as in chemical bonds, the adsorption process is called chemical adsorption of chemisorption. It is definite and irreversible. The exact amount of gas adsorbed is not related to the critical temperature of the gas. It also increases with surface area. There is a strong force of attraction as same as to chemical bond. It forms unimolecular layers. 

5.2 Catalysis

Under this section of NCERT Solutions Class 12 Chemistry Chapter 5, students will learn about catalysis. All reactants need to overcome specific energy; activation energy is the difference between the energy of the transition state and the reactant species. Some reactant molecules have sufficient kinetic energy to overcome this energy barrier, whereas others don’t. Therefore, not all reactions happen at the same rate in general conditions. Thus, specific reagents are added, lowering the required activation energy to convert reactants to products. These reagents are called catalysts, and this process of reducing the activation energy is called catalysis. 

Catalysis of chemical reactions is divided into two categories:

• Homogeneous Catalysis: The Homogeneous catalysis of chemical reactions is a process where the reactants are involved in the reaction, and the catalyst is in the same phase. Ex: hydrolysis of glucose in the presence of acid.
• Heterogeneous Catalysis: The Heterogeneous catalysis of chemical reactions is a process where the reactants involved in the reaction, and the catalyst, are in different phases. Forex: reaction of hydrogen and nitrogen in iron to form ammonia.

Mechanism of Heterogeneous Catalysis of Chemical Reactions: Students will also learn the mechanism of heterogeneous catalysis of chemical reactions under NCERT Solutions Class 12 Chemistry Chapter 5. The modern theory of adsorption has a five-step mechanism for the catalysis of chemical reactions. These steps are as follows:

• General Introduction and diffusion of reactant molecules on the catalytic surface.
• Adsorption of molecules of reactants on the catalytic surface.
• Formation of intermediate on a catalytic surface by a chemical reaction between the reactant molecules.
• Desorption of product molecules from the catalytic.
• Diffusion of product molecules away from the catalytic surface to form final products.

What is catalysis? A catalyst is defined as a substance that increases the rate of a chemical reaction without changing itself. The process by which a catalyst enhances the reaction rate is known as catalysis. 

How do catalysts work? For reactants to react and give a final product, reactant molecules have threshold energy, and the exact number of molecules with this energy should also be more than a threshold value. This energy is known as activation energy. 

Example of some heterogeneous catalysts: Under the Oxidation of sulphur dioxide into sulphur trioxide in front of (platinum metal or vanadium pentoxide )as a catalyst, reactants are in a gaseous state while the catalyst is in a solid state.

2SO2(g)+O2(g)→Pt(s)2SO3

Enzymes

The NCERT Solutions Class 12 Chemistry Chapter 5 also defines enzymes. Enzymes are nitrogenous compounds that plants and animals generate. It is a high molecular mass protein molecule and forms colloidal solutions with water. It is a very effective catalyst. They catalyse many reactions in animals’ and plants’ bodies to maintain life processes; Thus, enzymes are called biochemical catalysts. 

Enzyme catalysed Reactions: Decomposition of Urea converts into Ammonia and Carbon Dioxide. Urease enzyme is used as an enzyme catalyst.

5.4 Classification of colloids

Under NCERT Solutions Class 12 Chemistry Chapter 5, Colloids are classified:

Based on the physical state of the dispersed phase and dispersed medium: 

Based on the nature of Interaction Between the Dispersed Phase and Dispersed Medium

• Lyophilic Colloids(liquid loving): A few substances can form colloids directly by adding them to a suitable liquid(dispersion medium). These colloids are called lyophilic colloids. Examples of these substances are gum, gelatine, starch and rubber. It is also known as Reversible sols.
• Lyophobic colloids (liquid hating): A few substances cannot form colloids by directly adding them to a liquid. Colloidal sols are made up of unique methods known as lyophobic colloids. Examples of these substances are metals and metal sulphides. They are also known as Irreversible colloids. 

Based on Types of Particles of the Dispersed Phase-

• Multimolecular Colloids: Many particles(atoms or molecules) of the dispersed phase combine to form species with colloidal particle size. These colloids are known as multimolecular colloids. Eg-gold sol.
• Macromolecular colloids: Substances with large molecules in suitable solvents form solutions, but these macromolecules might be in the colloidal range. These solutions are known as macromolecular colloids and resemble real solutions in many ways. E.g., Starch, Cellulose.
• Associated Colloids: A few substances at high concentrations act as colloids due to the formation of aggregates. Therefore at low concentrations, they behave like normal strong electrolytes. These aggregates formed are called micelles. Such colloids are called associated colloids. 

Properties of Colloids- Brownian Movement: Under NCERT Solutions class 12 Chemistry chapter 5 Brownian movement can be explained as the ceaseless zigzag movement of the colloidal particles in a colloidal solution. It is based on the size of the particle’s viscosity of the colloid. This movement is responsible for the stability of sols. 

5.5 Emulsions

Emulsions are colloids where both the dispersion phase and dispersion medium are liquids. These two liquids are immiscible or partially miscible. Generally, one of the liquids is water. There are two types of emulsions. 

Oil dispersed in water (o/w type)- Water acts as a dispersion medium, for example –milk and vanishing cream.

Water dispersed in oil (w/o type)- Oil acts as a dispersion medium, For example- Butter, Cream. 

5.6 Applications of Colloids 

Under NCERT Solutions Class 12 Chemistry Chapter 5 Exercise 5.5, students may study the application of colloids. 

1. Purification drinking water – Alum is a mix of impure water to thicken the suspended impurities and make water fit for drinking.
2. Medicines – Many medicines are colloidal in nature. Colloidal medicines are more effective. E.g., Argyrol is a silver sol used as an eye lotion.
3. Industrial products- Paints, inks, synthetic plastics, rubber, cement, and graphite lubricants are all colloids.

Students may refer to Extramarks study material that includes revision notes, important questions, and sample questions pertaining to NCERT Solutions class 12 Chemistry chapter 5.

NCERT Solutions Class 12 Chemistry Chapter 5 Exercise & Solutions

NCERT Solutions Class 12 Chemistry Chapter 5 Exercise and Solutions are vital aspects of the study material that students refer to. The solutions provided in this section help students understand how to answer important questions to ensure that they have covered all aspects of the topic. 

Some of the essential exercise questions and answers for NCERT Solutions Class 12 Chemistry chapter 5 include topics such as Demulsification, Coagulation, Dialysis colloidal particles, and more. The exercise and answer solutions provided by Extramarks are detailed in nature to ensure that students can understand the concept without having to depend on teachers. They prepare students to face questions of any difficulty level during examinations.

NCERT Solutions Class 12 Chemistry Chapter 5 is explained in detail by the experts of Extramarks. Students may refer to the various study material provided, which concentrates more on the key points. In addition to Chapter 5, students can access NCERT Solution for all other Chemistry chapters of Class 12. Furthermore, students can click on the likes provided below to access the study material of different classes and subjects.