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| Science NCERT Exemplar Solutions (Class 12th) | ||||||||||||||
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Class 12th Chemistry NCERT Exemplar Solutions
1. Solid State
This chapter explores the nature and properties of the solid state of matter. It begins by distinguishing between amorphous and crystalline solids based on the arrangement of their constituent particles. The chapter focuses on crystalline solids, describing their classification based on bonding forces (ionic, covalent, molecular, metallic). It introduces the concepts of crystal lattices and unit cells, detailing the structure of simple cubic, body-centred cubic (BCC), and face-centred cubic (FCC) cells. Key calculations for packing efficiency, density, and the relationship between particle radius and edge length are covered. The chapter also discusses imperfections or defects in solids (like Schottky and Frenkel defects) and their profound impact on the electrical and magnetic properties of materials.
2. Solutions
This chapter provides a comprehensive study of liquid solutions. It details various methods for expressing solution concentration, such as molarity ($M$), molality ($m$), and mole fraction ($\chi$). A central theme is Raoult's Law, which describes the vapour pressure of solutions containing volatile or non-volatile solutes, leading to the concepts of ideal and non-ideal solutions (with positive and negative deviations). The chapter thoroughly explains the four colligative properties, which depend only on the number of solute particles: relative lowering of vapour pressure, elevation in boiling point ($\Delta T_b = K_b m$), depression in freezing point ($\Delta T_f = K_f m$), and osmotic pressure ($\pi = iCRT$). The concept of the van't Hoff factor ($i$) is introduced to account for the dissociation or association of solutes.
3. Electrochemistry
Electrochemistry is the study of the relationship between chemical energy and electrical energy. This chapter covers the functioning of electrochemical cells, dividing them into Galvanic (Voltaic) cells, which generate electricity from spontaneous redox reactions, and Electrolytic cells, which use electrical energy to drive non-spontaneous reactions. It introduces standard electrode potential ($E^\circ$), the electrochemical series, and the Nernst equation ($E = E^\circ - \frac{RT}{nF}\ln Q$) for calculating cell potential under non-standard conditions. The chapter also discusses electrolytic conductance, molar conductivity ($\Lambda_m$), and Kohlrausch's law. Practical applications like batteries, fuel cells, and the electrochemical principles behind corrosion are also detailed.
4. Chemical Kinetics
Chemical kinetics is the branch of chemistry concerned with the rates and mechanisms of chemical reactions. This chapter defines the rate of reaction and explains how it is influenced by factors like concentration, temperature, and catalysts. It introduces the concepts of the rate law, rate constant ($k$), order of a reaction, and molecularity. The chapter derives and applies the integrated rate equations for zero and first-order reactions to calculate reaction times and half-life ($t_{1/2}$). The temperature dependence of reaction rates is explained using the concept of activation energy ($E_a$) and the Arrhenius equation ($k = Ae^{-E_a/RT}$), which are further rationalized by the collision theory.
5. Surface Chemistry
This chapter explores phenomena that occur at surfaces or interfaces. It is divided into three main topics. Adsorption, the accumulation of substances on a surface, is discussed, distinguishing between physical adsorption (physisorption) and chemical adsorption (chemisorption). Catalysis explains how catalysts alter reaction rates, covering homogeneous, heterogeneous, and enzyme catalysis. The third topic is colloids, which are systems where one substance of microscopically dispersed insoluble particles is suspended throughout another substance. The chapter details their classification, preparation, purification, and characteristic properties like the Tyndall effect and Brownian movement. The role of emulsions and gels is also covered.
6. General Principles And Processes Of Isolation Of Elements
This chapter focuses on the principles and practices of metallurgy, the science of extracting metals from their natural sources (ores). It outlines the three major steps involved in extraction. First is the concentration of ores to remove unwanted gangue. The second step involves the isolation of the metal from the concentrated ore, usually through conversion to an oxide followed by reduction (smelting). The final step is the refining of the crude metal to achieve high purity, using methods like electrolysis or zone refining. The chapter illustrates these principles with thermodynamic and electrochemical considerations, detailing the extraction of key metals like iron (in a blast furnace), copper, zinc, and aluminium (Hall-Héroult process).
7. The P-Block Elements
This chapter provides a detailed study of the p-block elements from Group 15 to Group 18. For each group (Nitrogen family, Oxygen family, Halogens, and Noble Gases), it discusses the general trends in electronic configuration, atomic properties, oxidation states, and chemical reactivity. It explains the anomalous behavior of the first element in each group. The chapter gives a thorough account of the preparation, properties, and structures of important compounds, such as ammonia (Haber's process), nitric acid (Ostwald's process), ozone, sulphur allotropes, sulfuric acid (Contact process), interhalogen compounds, and the compounds of xenon (e.g., $XeF_4, XeF_6$).
8. The D-Block And F-Block Elements
This chapter covers the chemistry of the transition metals (d-block) and the inner transition metals (f-block). It discusses the electronic configurations and characteristic properties of transition elements, such as their variable oxidation states, formation of coloured ions, magnetic properties, and catalytic activity. The preparation and properties of two important compounds, potassium dichromate ($K_2Cr_2O_7$) and potassium permanganate ($KMnO_4$), are detailed. For the f-block elements, the chapter focuses on the Lanthanoids, explaining the phenomenon of Lanthanoid contraction and its consequences. A brief comparison between Lanthanoids and Actinoids is also provided.
9. Coordination Compounds
This chapter introduces the fascinating world of coordination compounds. It starts with Werner's theory and defines key terminology like ligands, coordination number, and coordination sphere. A significant focus is on the systematic IUPAC nomenclature for naming these complex compounds. The chapter explains the various types of isomerism (structural and stereo) that these compounds exhibit. Two major theories are used to explain the bonding and properties: Valence Bond Theory (VBT), which uses hybridization to explain geometry and magnetic properties, and Crystal Field Theory (CFT), which explains the colour and magnetic properties based on the splitting of d-orbital energies. The stability and importance of coordination compounds in analytical and biological systems are also highlighted.
10. Haloalkanes And Haloarenes
This chapter marks the beginning of organic chemistry, focusing on halogen derivatives. It covers the nomenclature, preparation methods, and physical properties of haloalkanes and haloarenes. The core of the chapter lies in their chemical reactions. For haloalkanes, the mechanisms of nucleophilic substitution reactions ($S_N1$ and $S_N2$) and elimination reactions are discussed in detail, including their stereochemical aspects. For haloarenes, the chapter explains their lower reactivity towards nucleophilic substitution and their characteristic electrophilic substitution reactions. The uses and environmental impact of some polyhalogen compounds are also mentioned.
11. Alcohols, Phenols And Ethers
This chapter deals with three important classes of oxygen-containing organic compounds. It discusses the nomenclature, preparation, and properties of alcohols, phenols, and ethers. The chapter explains the influence of hydrogen bonding on their physical properties. A key focus is the comparison of the acidity of alcohols and phenols, explaining why phenols are more acidic. It details the characteristic reactions for each class, including the oxidation and dehydration of alcohols, and the electrophilic substitution reactions of phenols (e.g., Kolbe's and Reimer-Tiemann reactions). For ethers, the Williamson synthesis and their cleavage reactions with hydrogen halides are covered.
12. Aldehydes, Ketones And Carboxylic Acids
This chapter is dedicated to organic compounds containing the carbonyl group ($>C=O$) and the carboxyl group ($-COOH$). It covers the nomenclature and preparation of aldehydes, ketones, and carboxylic acids. The chapter explains the mechanism of nucleophilic addition to the carbonyl group, a characteristic reaction of aldehydes and ketones. It details several important named reactions, including the Aldol condensation, Cannizzaro reaction, and various reduction reactions. For carboxylic acids, it discusses their higher acidity compared to phenols and details reactions like esterification and the Hell-Volhard-Zelinsky (HVZ) reaction.
13. Amines
This chapter focuses on amines, the organic derivatives of ammonia. It covers their classification, nomenclature, and preparation methods, including the Hoffmann bromamide degradation and Gabriel phthalimide synthesis. A major theme is the basic character of amines, with a detailed comparison of the basicity of primary, secondary, and tertiary amines. The chapter describes their key chemical reactions, including tests to distinguish between the different classes of amines (Hinsberg test). A significant section is devoted to the preparation and synthetic utility of arenediazonium salts, which are important intermediates for preparing a variety of aromatic compounds via reactions like the Sandmeyer reaction.
14. Biomolecules
This chapter explores the chemistry of life, focusing on the complex organic molecules that form the basis of living organisms. It provides a detailed study of Carbohydrates, classifying them and discussing the structure of glucose and sucrose. Proteins are described as polymers of $\alpha$-amino acids, with a focus on peptide bonds and the four levels of protein structure (primary, secondary, tertiary, and quaternary). The chapter also covers Nucleic Acids, detailing the structure of DNA and RNA and their roles in heredity. Finally, it provides an overview of Vitamins, classifying them and discussing diseases caused by their deficiency.
15. Polymers
This chapter introduces the world of polymers—giant molecules made of repeating structural units called monomers. It classifies polymers based on their source, structure, and mode of polymerization. The chapter details the two main types of polymerization reactions: addition polymerization (e.g., forming polyethene) and condensation polymerization (e.g., forming nylon). It discusses the preparation, properties, and uses of important commercial polymers like Teflon, PVC, Nylon 6,6, and Bakelite. The chapter also covers the concept of rubber vulcanization and introduces the important and growing field of biodegradable polymers, which offer a solution to environmental pollution caused by plastic waste.
16. Chemistry In Everyday Life
This chapter highlights the direct impact of chemistry on our daily lives, focusing on three main areas. Medicines (Drugs) are discussed, with a classification of therapeutic agents like antacids, antihistamines, tranquillizers, and antimicrobials (antibiotics, antiseptics). The chapter then explores Chemicals in Food, such as preservatives, artificial sweeteners, and antioxidants. Finally, it covers Cleansing Agents, explaining the chemistry behind the action of soaps and synthetic detergents, including the mechanism of micelle formation. This chapter provides a fascinating look at how chemical knowledge is applied to improve health, hygiene, and the quality of life.
Sample Paper I
This is the first comprehensive Sample Paper designed for Class 12 Chemistry, based on the NCERT Exemplar format. It serves as an essential practice tool, featuring a well-rounded collection of questions spanning the entire syllabus. By solving this paper, students can gauge their understanding of complex concepts, practice numerical problems, and learn to manage their time effectively under exam conditions. It is a critical resource for self-assessment and for fine-tuning preparation strategy before the final board examination.
Sample Paper II
This is the second Sample Paper provided in the series, offering another opportunity for rigorous practice. It presents a fresh set of questions covering all 16 chapters, designed to test a deep understanding of the subject matter. Working through this additional paper helps students to reinforce their knowledge, improve their problem-solving speed, and build greater confidence. Engaging with both sample papers ensures a thorough revision of the syllabus, preparing students to tackle a wide variety of questions with proficiency in their Chemistry examination.