2nd Year Chemistry Textbook PDF

BUREAU’S HIGHER SECONDARY (+2) VOL. - II Dr. A. K. Das Dr. H. K. Patnaik Former Chairman, CHSE, Odisha Former Principal, Govt. College, Bhubaneswar. Rourkela....

BUREAU’S HIGHER SECONDARY (+2) VOL. - II Dr. A. K. Das Dr. H. K. Patnaik Former Chairman, CHSE, Odisha Former Principal, Govt. College, Bhubaneswar. Rourkela. Dr. S. Behera Dr. G. C. Dash Former Principal, D. D. College, Former Principal, Keonjhar. S.C.S. (Autonomous) College, Puri. Dr. A. K. Panigrahi Dr. Hrushikesh Mohanty Former Director, Odisha State Bureau of Associate Professor & HOD, Chemistry, Textbook Preparation and Production, B.J.B. Autonomous College, Bhaubaneswar. Bhubaneswar. Dr. Santosini Patra Dr. B. C. Singh Associate Professor in Chemistry Former Professor of Chemistry, R.D. Women's University, Bhubaneswar Ravenshaw College, Cuttack. Dr. Panchanan Gouda Dr. B. K. Mohapatra Associate Professor & H.O.D., Chemistry, Former Chairman, CHSE, Odisha, Khallikote University, Berhampur. Bhubaneswar. Dr. I. B. Mohanty Dr. J. N. Kar Deputy Director Former Principal, Govt. College, Phulbani. Department of Higher Education, Odisha Dr. Sakuntala Jena Asst. Professor, Department of Chemistry, Govt. Women's College, Dhenkanal. PUBLISHED BY THE ODISHA STATE BUREAU OF TEXTBOOK PREPARATION AND PRODUCTION PUSTAK BHAVAN, BHUBANESWAR. Published by : THE ODISHA STATE BUREAU OF TEXTBOOK PREPARATION AND PRODUCTION, Pustak Bhavan, Bhubaneswar, Odisha, India. First Edition : 2000 / 7000 Revised and Enlarged Edition : 2002 / 3000 Revised Edition : 2004 / 1000 Revised Edition : 2006 / 1000 Revised Edition : 2008/2000 Reprint - 2010/2000 Revised Edition : 2013/2000 New Edition : 2017 / 5000 Publication No : 197 ISBN : 978-81-8005-388-7 © Reserved by the Odisha State Bureau of Textbook Preparation and Production, Bhubaneswar. No part of this publication may be reproduced in any form without the prior written permission of the publisher. Typesetting and Diagram by : PRINT-TECH OFFSET PVT. LTD., Bhubaneswar Printed at : PRINT-TECH OFFSET PVT. LTD., Bhubaneswar Price : ` 300/- (Rupees Three Hundred Only)  FOREWORD (New Edition - 2017) The Council of Higher Secondary Education, Odisha has revised the Courses of Studies in Chemistry for its Examination, 2018 and onwards. It is really heartening to know that the Chemistry, Vol-II is an exclusive textbook of CHSE and is being published by the Odisha State Bureau of Text Book Preparation and Production, Bhubaneswar. I acknowledge with thanks to the Board of Writers and Reviewers who have worked hard in writing the chapters of the book and setting new pattern of questions as per the requirement of the new syllabus of CHSE. I would like to express my thanks to Dr. Jibanananda Kar, Dr. Akhil Krishna Panigrahi, Dr. Gobinda Chandra Dash, Dr. Hrushikesh Mohanty, Dr. Panchanan Gouda, Dr. Santosini Patra and Dr. Sakuntala Jena for taking pain and strain of doing arduous work in preparing the book within the frame work of the new syllabus of CHSE. Improvement has no limit especially when one aims at excellence. The Bureau welcomes constructive suggestions from the students as well as the teachers to make the book more purposeful. Sri Umakanta Tripathy Director Odisha State Bureau of Text Book Preparation and Production, Pustak Bhavan, Bhubaneswar, Odisha  PREFACE India is on the verge of a great leap into the global scientific and technological advancement in the New Millennium. Our Universities and Council of Higher Secondary Education have taken up the upgrading of science curriculum as a challenge. Society is becoming largely knowledge based. To prepare our young students to achieve the goal, Council of Higher Secondary Education, Odisha has revised the syllabus of all science subjects and has taken up the challenge to arm our students with advanced scientific education. The biggest challenge in the present times in the field of scientific education is the preparation of textbooks suited to the needs of the students. Some of the most experienced, learned and brilliant teachers of the State have made attempts towards fulfilling the national need of providing a good textbook in Chemistry for +2 students. As a result the book titled +2 Chemistry has been prepared in accordance with the new syllabus of C.H.S.E. Odisha which will be effective for the students who will be admitted in 2016 and onwards. This book has many special features, the salient ones of which may be enumerated as follows : (i) The text book has been prepared keeping in view the type of questions set in the +2 as well as entrance examinations. (ii) The subject matter has been put in a lucid manner and in a simple language to be easily followed by the students. (iii) Large numbers of numerical problems have been worked out. (iv) Neat diagrams are given to provide suitable explanation of the texts. (v) Large number of questions of very short answer type, short answer type, multiple choice type and long answer type including questions of H. S. Examinations are given in each chapter. (vi) At the end of every chapter, summary of the topics dealt in the chapter is given under Chapter at a glance. The authors express their gratitude to the authorities of C.H.S.E. for accepting them as the members of Board of Editors and to the ODISHA STATE BUREAU OF TEXTBOOK PREPARATION AND PRODUCTION for publishing the book. The authors sincerely hope that their endeavour would fulfil the need of students. There may be minor errors of omissions and commissions in the book. The authors welcome constructive criticism and suggestions for the improvement of the book. Bhubaneswar Board of Writers 14.3.2017  COURSES OF STUDIES IN CHEMISTRY (THEORY) FOR HIGHER SECONDARY EXAMINATION (Effective from 2016 Admission Batch) SECOND YEAR Course Structure Unit Title Marks I Solid State II Solutions III Electrochemistry 23 IV Chemical Kinetics V Surface Chemistry.......................................................................................................................... VI Isolation of Elements VII p-Block Elements VIII d- and f- Block Elements 19 IX Coordination Compounds.......................................................................................................................... X Haloalkanes and Haloarenes XI Alcohols, Phenols and Ethers XII Aldehydes, Ketones and Carboxylic Acids XIII Organic Compounds containing Nitrogen 28 XIV Biomolecules XV Polymers XVI Chemistry in Everyday Life Total : 70 Unit - I : Solid State Classification of solids based on different binding forces: molecular, ionic, covalent and metallic solids, amorphous and crystalline solids (elementary idea). Unit cell in two dimensional and three dimensional lattices, calculation of density of unit cell, packing in solids, packing efficiency, voids, number of atoms per unit cell in a cubic unit cell, point defects, electrical and magnetic properties. Band theory of metals, conductors, semiconductors and insulators and n & p type semiconductors. Unit II : Solutions Types of solutions, expression of concentration of solutions of solids in liquids, solubility of gases in liquids, solid solutions, colligative properties - relative lowering of vapour pressure, Raoult’s law, elevation of boiling point, depression of freezing point, osmotic pressure, determination of molecular masses using colligative properties, abnormal molecular mass, van’t Hoff factor. Unit III : Electrochemistry Redox reactions, electrolytes and non-electrolytes, conductance in electrolytic solutions, specific and molar conductivity, variation of conductivity with concentration, Kohlrausch’s law, electrolysis and laws of electrolysis (elementary idea), dry cell electrolytic cells and Galvanic cells, lead accumulator, EMF of a cell, standard electrode potential, Nernst equation and its application to chemical cells, Relation between Gibbs energy change and emf of a cell, fuel cells, corrosion. Unit IV : Chemical Kinetics Rate of a reaction (Average and instantaneous), factors affecting rate of reaction: concentration, temperature, catalyst, order and molecularity of a reaction, rate law and specific rate constant, integrated rate equations and half life (only for zero and first order reactions), concept of collision theory (elementary idea, no mathematical treatment). Activation energy, Arrhenius equation. Unit V : Surface Chemistry Adsorption - physisorption and chemisorption, factors affecting adsorption of gases on solids, catalysts, homogenous and heterogenous activity and selectivity; enzyme catalysis, colloidal state, distinction between true solutions,colloids and suspension; lyophilic, lyophobic, multimolecular and macromolecular colloids; properties of colloids; Tyndall effect, Brownian movement, electrophoresis, coagulation, emulsion - types of emulsions. Unit VI : General Principles and Processes of Isolation of Elements Principles and methods of extraction - concentration, oxidation, reduction - electrolytic method and refining; occurrence and principles of extraction of aluminium, copper, zinc and iron. Unit VII : p - Block Elements Group15 Elements: General introduction, electronic configuration, occurrence, oxidation states, trends in physical and chemical properties; Nitrogen : preparation properties & uses; compounds of nitrogen, preparation and properties of ammonia and nitric acid, oxides of nitrogen (Structure only); Phosphorus - allotropic forms, compounds of phosphorus: preparation and properties of phosphine, halides PCl 3, PCl5 and oxoacids (elementary idea only). Group 16 Elements: General introduction, electronic configuration, oxidation states, occurrence, trends in physical and chemical properties, dioxygen: Preparation, Properties and uses, classification of oxides, Ozone, Sulphur: allotropic forms; compounds of sulphur: Preparation properties and uses of sulphur dioxide, sulphuric acid: industrial process of manufacture, properties and uses; oxoacids of sulphur (Structures only). Group 17 Elements: General introduction, electronic configuration, oxidation states, occurrence, trends in physical and chemical properties; compounds of  halogens, Preparation properties and uses of chlorine and hydrochloric acid,interhalogen compounds, oxoacids of halogens (structure only). Group 18 Elements : General introduction,electronic configuration, occurrence, trends in physical and chemical properties, uses. Unit VIII : d and f Block Elements General introduction, electronic configuration, occurrence and characteristics of transition metals, general trends in properties of the first row transition metals - metallic character, ionization enthalpy, oxidation states, ionic radii, colour, catalytic property, magnetic properties, interstitial compounds, alloy formation, preparation and properties of K2 Cr2O7 and KMnO4. Lanthanoids - Electronic configuration, oxidation states, chemical reactivity and lanthanoid contraction and its consequences. Actinoids - Electronic configuration, oxidation states, chemical reactivity and lanthanoid contraction and its consequences. Actinoids - Electronic configuration, oxidation states and comparison with lathanoids. Unit IX : Coordination Compounds Coordination compounds - Introduction, ligands, coordination number, colour, magnetic properties and shapes, IUPAC nomenclature of mononuclear coordination compounds. Bonding, Werner’s therory, VBT and CFT; structure and stereoisomerism, importance of coordination compounds (in qualitative analysis, extraction of metals and biological system). Unit X : Haloalkanes and Haloarenes Haloalkanes : Nomenclature, nature of C-X bond, physical and chemical properties, mechanism of substitution reactions, optical rotation. Haloarenes : Nature of C - X bond, substitution reactions (Directive influence of halogen in monosubstituted compounds only. Uses and environmental effects of - dichloromethane, trichloromethane, tetrachloromethane, iodoform, freons, DDT, BHC. Unit XI : Alcohols, Phenols and Ethers Alcohols : Nomenclature, methods of preparation, physical and chemical properties (of primary alcohols only), identification of primary, secondary and tertiary alcohols, mechanism of dehydration, uses with special reference to methanol and ethanol. Phenols : Nomenclature, methods of preparation, physical and chemical properties, acidic nature of phenol, electrophilic substitution reactions, uses of phenols. Ethers : Nomenclature, methods of preparation, physical and chemical properties uses. Unit XII : Aldehydes, Ketones and Carboxylic Acids Aldehydes and Ketones : Nomenclature, nature of carbonyl group, methods of preparation, physical and chemical properties, mechanism of nucleophilic addition, reactivity of alpha hydrogen in aldehydes uses. Carboxylic Acids : Nomenclature, acidic nature, methods of preparation, physical and chemical properties, uses. Unit XIII : Organic compunds containing Nitrogen Amines : Nomenclature, classification, structure, methods of preparation, physical and chemical proporties, uses, identification of primary, secondary and teritary amines. Cyanide and Isocyanides - will be mentioned at relevant places in context Diazonium salt - Preparation, chemical reactions and importance in synthetic organic chemistry. Unit XIV : Biomolecules Carbohydrates - Classification (aldoses and ketoses) Monosaccharides (glucose and fructose), D-L configuration, oligosaccharides (sucrose, lactose, maltose) polysaccharides (starch, cellulose, glycogen), importance. Proteins - Elementary idea of a - amino acids, peptide bond, polypeptide, proteins, structure of proteins-primary secondary, tertiary structure and quaternary structure(qualitative idea only), denaturation of proteins, enzymes. Hormones - Elementary idea excluding structure Vitamins - Classification and functions Nucleic Acids : DNA and RNA Unit XV : Polymers Classification-Natural and synthetic, methods of polymerization(addition and condensation)co polymerization, some important polymers : natural and synthetic like polythene, nylon, polyester, bakelite, rubber. Biodegradable and non- biodegradable polymers. Unit XVI : Chemistry in Everyday life Chemicals in medicines - Analgesics, tranquilizers antiseptics, disinfectants, antimicrobials, antifertility, drugs, antibiotics, antacids, antihistamines. Chemicals in food - Preservations, artificial sweetening agents, elementary idea of antioxidants Cleansing agents - Soap and detergents, cleansing action......  CONTENTS Chapter Subjects Pages UNIT - I CHAPTER - 1 : SOLID STATE 1 - 26 1.1. Characteristic properties of solids, 1.2. Classification of solids: Crystalline solids, Amorphous solids, Ionic solids, Covalent solids, Metallic solids, Molecular solids, 1.3. Crystal lattices and unit cells, Packing in solids, 1.4. Types of cubic crystals, 1.5. Calculation of density of unit cells, 1.6. Interstices or Interstitial voids, 1.7. Co-ordination number, 1.8. Point defects, 1.9. Electric and Magnetic properties of metals: Band theory of metals, conductors, insulators, semiconductors- n & p type semiconductors, Magnetic properties of solids. UNIT - II CHAPTER - 2 : SOLUTIONS 27 - 67 Characteristics of a solution : Types of solutions, 2.2. Solubility, 2.3. Concentration of a solution, 2.4. Solubility of gases in liquids, 2.5. Vapour pressure, 2.6. Ideal and non-ideal solutions, 2.7. Colligative properties of dilute solutions- Relative lowering of vapour pressure, Raoult's law, 2.8. Elevation of boiling point (Ebullioscopy), 2.9. Depression of freezing point (Cryoscopy), 2.10. Osmotic pressure, 2.11. Abnormal molecular mass, van't Hoff Factor. UNIT - III CHAPTER - 3 : ELECTROCHEMISTRY 68 - 108 3.1. Introduction : Redox reaction, Electrolytes and non- electrolytes, 3.2. Arrhenius theory of electrolytic dissociation, 3.3. Strong and weak eletrolytes, 3.4. Electrolysis, 3.5. Faraday's laws of electrolysis, 3.6. Applications of electrolysis, 3.7. Electrolytic conductance : specific, equivalent and molar conductance, 3.8. Measurement of conductance, 3.9. Effect of dilution on equivalent conductance, 3.10. Kohlrausch's law, 3.11. Electrochemical cells: Galvanic cell, 3.12. Cell reactions, 3.13. Electrode potential, 3.14. Single electrode potential, 3.15. Nernst equation, 3.16. Electromotive force (E.M.F) of a cell, 3.17. Electrochemical cells : Primary cells (Dry cells), Lead accumulator, Nickel-cadmium rechargeable cells, Fuel cells, 3.18. Electrochemical series, Application of electrochemical series, 3.19. Corrosion.  Chapter Subjects Pages UNIT - IV CHAPTER - 4 : CHEMICAL KINETICS 109 - 146 4.1. Types of chemical reactions, 4.2. The rate of a reaction - Determination of rate of reaction, Instantaneous and Average rate of reaction, rate constant, units of rate constant, Rate of reaction and rate constant, Factors influencing the rate of a reaction : concentration, catalyst, temperature, surface area and radiations, 4.3. Molecularity of a reaction, 4.4. Order of a reaction, 4.5. Rate equations - Rate equation of first order reaction, Rate equation of the zero order reaction, Half life period and fractional life period, 4.6. Activation Energy, Arrhenius equation, 4.7. Collision theory for unimolecular reaction. UNIT - V CHAPTER - 5 : SURFACE CHEMISTRY 147 - 186 5.1. Adsorption : Types of adsorption - physical adsorption and chemisorption, 5.2. Adsorption of gases on solids, 5.3. Freundlich's adsorption isotherm, 5.4. Langmuir adsorption isotherm, 5.5. Applications of adsorption, 5.6. Catalyst : characteristics of catalyst, types of catalysis : Homogeneous and Heterogeneous catalysis, 5.7. Enzyme catalysis, 5.8. Effect of the catalyst on activation energy. 5.9. Adsoption theory of heterogeneous catalysis, 5.10. Important features of solid catalysts - Activity and selectively, 5.11. Colloidal state, 5.12. Types of colloidal system - True solutions, colloidal solution and suspensions, 5.13. Classification of colloids: Lyophilic and Lyophobic colloids, 5.14. Classification of colloids on the basis of molecular size - multimolecular, macromolecular and associated colloids (Micelles), 5.15. Preparation of colloidal solution, 5.16. Properties of colloidal solution : Tyndall effect, Brownian movement, zeta potential; Electrophoresis, Coagulation of colloidal sol (Flocculation), coagulation of lyophobic sol, lyophobic sol, 5.17. Application of colloids, 5.18. Emulsion : Type of emulsions, properties and uses of emulsions. UNIT - VI CHAPTER - 6 : GENERAL PRINCIPLES AND PROCESSES OF 187 - 230 ISOLATION OF ELEMENTS 6.1. Introduction, 6.2. Occurrence of metal in nature, 6.3. Extraction of metals or Metallurgy : concentration,  Chapter Subjects Pages calcination and roasting, smelting, reduction of metal oxide to free metal, 6.4. Thermodynamic principles of metallurgy, 6.5. Extraction of iron from its oxide ores. 6.6. Copper : Extraction, 6.7 Zinc-Extraction, 6.8. Electrochemical principles of metallurgy - Extraction of Aluminium, 6.9. Extraction of non- metals by oxidation-Isolation of chlorine, 6.10. Refining of metals, 6.11. Uses of metals. UNIT - VII p-BLOCK ELEMENTS CHAPTER - 7 : GROUP 15 ELEMENTS : NITROGEN FAMILY 231 - 259 7.1. Occurrence, 7.2. Trends in physical properties, 7.3. Trends in chemical properties, 7.4. Anomalous behaviour of Nitrogen, 7.5. Dinitrogen : Preparation, properties and uses, 7.6. Compounds of Nitrogen : Preparation, properties and uses of Ammonia, 7.7. Preparation, properties and uses of Nitric acid, 7.8 Oxides of Nitrogen - their structures. 7.9. Phosphorus : Allotropic forms, 7.10. Preparation, properties and uses of phosphine (PH3), 7.11. Phosphorus halides : preparation and properties of phosphorus trichloride and phosphorus pentachloride, their structures, 7.12. Oxo acids of phosphorus : Formulae, oxidation state of phosphorus in them, their structures. CHAPTER - 8 : GROUP 16 ELEMENTS : OXYGEN FAMILY 260 - 294 8.1. Occurrence, 8.2. Trends in physical properties, 8.3 Trends in chemical properties, 8.4. Anomalous behaviour of oxygen, 8.5. Dioxygen : preparation, properties and uses. 8.6. Classification of oxides, 8.7. Ozone, 8.8. Sulphur : Allotropic forms of sulphur, 8.9. Sulphur dioxide : preparation, properties and uses. 8.10. Sulphuric acid (H2SO4) - Laboratory and Industrial process of manufacture, properties and uses, 8.11. Oxo-acids sulphur - structures. CHAPTER - 9 : EQUILIBRIA 295 - 324 9.1. Occurrence, 9.2. Trends in physical properties, 9.3. Trends in chemical properties, 9.4. Anomalous behaviour of fluorine, 9.5. Chlorine : preparation, properties and uses, 9.6. Hydrogen chloride (Hydrochloric acid) : preparation, properties and uses, 9.7. Oxoacids of halogen : their structures, 9.8. Interhalogen compounds or Interhalogens : preparation, properties, structures and uses, 9.9. Pesudo halides or Pseudohalogens.  Chapter Subjects Pages CHAPTER - 10 : GROUP 18 ELEMENTS : NOBLE GASES 325 - 341 10.1. Introduction, 10.2. Occurrence, 10.3. Position of inert gases in the Periodic table, 10.4. Properties of Zero group elements, 10.5. Chemical properties - compounds of zero group elements - their properties, structures and uses. UNIT - VIII d - AND f - BLOCK ELEMENTS CHAPTER - 11 : d - BLOCK ELEMENTS : TRANSITION ELEMENTS 342 - 360 11.1. Transition metals, 11.2. General characteristics of transition elements : atomic radii, ionisation enthalpy, metallic properties, densities, melting and boiling points, variable oxidation states, formation of coloured compounds, formation of complex compounds, paramagnetism, catalytic activity and formation of alloys and interstitial compounds. 11.3. Potassium dichromate - preparation, properties and uses, 11.4. Potassium permanganate - preparation, properties and uses. CHAPTER - 12 : THE f-BLOCK ELEMENTS 361 - 371 THE LANTHANOIDS AND THE ACTINOIDS 12.1. Introduction, 12.2. The lanthanoids-electronic configuration, atomic and ionic sizes, lanthanoid contraction and its consequences, oxidation states, General characteristics of lanthanoids, uses, 12.3. The Actinoids : Electronic configuration, oxidation states, Ionic sizes and Actinoid contraction, General characteristics of actinoids, uses, 12.4. Comparison between Lanthanoids and Actinoids. UNIT - IX CHAPTER - 13 : CO-ORDINATION COMPOUNDS 372- 404 13.1. Normal salt, 13.2. Double salts, 13.3. Co-ordination compounds, 13.4. Definition of some important terms: co- ordination complex, central ion, Ligands, co-ordination number, co-ordination sphere, Types of ligands, 13.5. Werner's co- ordination theory, 13.6. Nomenclature of co-ordination compounds, IUPAC system, 13.7. Isomerism in co-ordination  Chapter Subjects Pages compounds, 13.8. Bonding in co-ordination compounds: The Valence Bond theory, The Crystal Field theory, 13.9. Bonding in metal carbonyls, 13.10. Stability of co-ordination compounds, 13.11. Importance of co-ordination compounds : In qualitative analysis, extraction of metals and in biological systems. 13.12. Organometallic compounds. UNIT - X HALOGENATED HYDROCARBONS (HALOALKANES AND HALOARENES) CHAPTER - 14 : HALOALKANES (ALKYL HALIDES) 405 - 421 14.1 Introduction, 14.2. Classification, 14.3. Monohalogen derivatives of alkanes, 14.4. Nomenclature, 14.5. Methods of preparation, 14.6. Properties - physical properties, chemical properties - Elimination reactions, mechanism of Nucleophilic substitution reactions : SN1 and SN2 mechanism, Reactions of alkyl halides. HALOARENES (ARYL HALIDES) 422 - 446 14.7. Nomenclature of halogen compounds, 14.8. Methods of preparation of haloarenes, 14.9. Properties : Physical properties, chemical properties : Nucleophilic substitution of aromatic halogen-mechanism, Electrophilic substitution reactions, directive influence of halogen in monosubstituted compounds, Miscellaneous reactions, 14.10. Chlorobenzene-preparation and properties, 14.11. Polyhalogen compounds : DDT, BHC, Trichloromethane or chloroform, Tetrachloromethane or carbon tetrachloride, Freons, 14.12. Arylalkalyl halides. UNIT - XI ALCOHOLS, PHENOLS AND ETHERS CHAPTER - 15 : ALCOHOLS 447 - 486 15.1. Introduction, 15.2. Classification of alcohols, 15.3. Monohydric alcohols, 15.4. Nomenclature of monohydric alcohols, 15.5. Isomerism in alcohols, 15.6. General methods of preparation, 15.7. Properties : Physical properties, Chemical properties, 15.8. Distinction between primary, secondary and  Chapter Subjects Pages tertiary alcohols, 15.9. Tests for alcoholic –OH group, 15.10. Manufacture of methyl alcohol from destructive distillation of wood, 15.11. Manufacture of ethyl alcohol from starchy materials 15.12. Some important conversions. CHAPTER - 16 : PHENOLS 487 - 500 16.1. Methods of preparation, 16.2. Properties - Physical properties, chemical properties : Acidity of phenols, esterification reaction, Electrophilic substitution reactions with mechanism, oxidation reaction and reaction with zinc dust. CHAPTER - 17 : ETHERS 501 - 521 17.1. Classification of ethers, 17.2. Nomenclature of ethers, 17.3. Structure of ethers, 17.4. Preparation ethers, 17.5. Physical properties of ethers, 17.6. Chemical properties : Reactions with mechanism, 17.7 Uses of ethers. UNIT - XII CHAPTER - 18 : ALDEHYDES AND KETONES 522 - 598 18.1. Introduction, 18.2. Nomenclature of carbonyl compounds, 18.3. Isomerism in aldehydes and ketones, 18.4. Structure of carbonyl group, 18.5. General methods of preparation of aldehydes and ketones, 18.6. Special methods of preparation for aromatic carbonyl compounds, 18.7. Properties of aldehydes and ketones : Physical properties, Chemical properties - Nucleophilic addition reactions with mechanism, reactions due to a - hydrogen of aldehydes, oxidation reactions, Miscellaneous reactions - reaction with NH3, Cannizzaro's reaction, Reaction with PCl5, Reduction reactions, Reaction with primary amines, Electrophilic substitution reactions in aromatic aldehydes and ketones, 18.8. Uses of aldehydes and ketones, 18.9. Important conversions. CHAPTER - 19 : CARBOXYLIC ACIDS 599 - 642 1 9. 1. G e n e r a l i n t r o d u c t i o n , 1 9. 2. N o me n c l a t u r e , 19.3. Isomerism, 19.4. Methods of preparation, 19.5. General properties : Physical and chemical properties, 19.6. Tests, 19.7. Uses of carboxylic acids, Some important conversions.  Chapter Subjects Pages UNIT - XIII ORGANIC COMPOUNDS CONTAINING NITROGEN CHAPTER - 20 : AMINES 643 - 673 20.1. Introduction, 20.2. Types of Amines - Aliphatic amines and Arylmines, 20.3. Nomenclature, 20.4. Isomerism, 20.5. General methods of preparation, 20.6. General properties : Basicity of aliphatic amines, basicity of aromatic amines, Physical properties, chemical properties, 20.7. Tests, 20.8. Separation of primary, secondary and tertiary amines, 20.9. Uses, 20.10. Conversions, 20.11. Distinction between primary, secondary and tertiary amines, 20.12. Cyanides and Isocyanides. CHAPTER - 21 : ARYL DIAZONIUM SALTS 674 - 684 21.1. Preparation of Benzene diazonium chloride, 21.2. Properties : Physical and chemical properties : Importance in synthetic organic chemistry through various reactions. 21.3. Some important conversions. UNIT - XIV CHAPTER - 22 : BIOMOLECULES 685 - 721 22.1. Introduction, 22.2. Carbohydrates : Classification, Monosaccharides, Oligasaccharides and Polysaccharides, Monosaccharides - Glucose : Preparation and structure, Fructose : Preparation and structure, Disaccharides : Sucrose, Maltose, Lactose - their structures, Polysaccharides - Starch, Amylopectin, Cellulose - their structures, Glycogen, 22.3. Aminoacids, Peptides and Polypeptides, 22.4. Proteins : Classification and structure of proteins, Biological roles of proteins, Denaturation of proteins, 22.5. Enzymes : Nature, properties of Enzymes, 22.6. Hormones : Chemical classes, source, function and effects of Hormones, Plant Hormones. 22.7. Vitamins : Classification and functions of vitamins. 22.8. Nucleic Acids : Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA), Biological functions of Nucleic acids.  Chapter Subjects Pages UNIT - XV CHAPTER - 23 : POLYMERS 722 - 745 23.1. Introduction, 23.2. Classification of polymers, 23.3. General method of polymerization, 23.4. Copolymerization, 23.5. Some important polymers : Polythene, Polyacrylonitrile (PAN) or Orlon, Polytetrafluoroethylene (PTFE) or Telflon, polyamides or Nylons, Polyesters, Bakelites; Rubber - Natural and synthetic rubber (cis-polybutadiene, Neoprene, Buna-N, Buna-S. UNIT - XVI CHAPTER - 24 : CHEMISTRY IN EVERYDAY LIFE 746 - 771 24.1. Introduction, 24.2. Chemicals in Medicine - Analgesics, Tranquilizers, Antiseptics and Disinfectants, Antimicrobials, Antibiotics, Antifertility Drugs, Antacids, Antihistamines, 24.3. Chemicals in Food - Preservatives, Artificial sweetening agents, Antioxidants, 24.4. Cleansing agents - Soaps and Detergents, Cleansing action of Soaps and Detergents..........  UNIT - I CHAPTER - 1 THE SOLID STATE The study of solids is mainly the study of crystals since most of the naturally occurring solids are crystalline in nature. Solids are characterised by definite shape, definite volume and fixed melting point.Besides compressibility, rigidity and high-mechanical strength are the properties of a solid. The molecules, atoms or ions that constitute a solid are closely packed and held by strong cohesive forces. So the solids have well ordered molecular arrangement. 1.1 CHARACTERISTIC PROPERTIES OF SOLIDS : 1. Shape : A solid has a definite shape. 2. Volume : A solid possesses a definite volume. It does not depend upon the size or shape of the container. 3. Rigidity : Solids are highly rigid. This is due to the fact that the molecules have definite positions and they cannot slide over each other to take up different positions. The interparticle attractions in them tend to arrange the particles in an orderly manner. 4. Compressibility : Solids are mainly incompressible. This is because the particles which constitute the solid are in close contact with one another. 5. Diffusion : The diffusion in case of solids is extremely small. This is due to the fact that the intermolecular forces of attraction holding the particles are very strong in solids which result in a close packing of particles in it. Thus movement of particles in a solid is very limited. 6. Melting point : The process of transformation of a solid into the liquid state at a particular temperature is called melting. The constant temperature at which a solid is transformed into the liquid state is called the melting point of the solid. At the melting point there is an equilibrium between the solid and liquid phases. 7. Crystalline state : Solids possess a crystalline structure. This is due to orderly arrangement of particles in solids. 2 +2 CHEMISTRY (VOL. - II) 1.2 CLASSIFICATION OF SOLIDS : A. Solids are broadly classified into two categories : (a) crystalline solids (b) amorphous solids. Crystalline solids : Crystalline solids are not only rigid and incompressible but also possess a regular orderly arrangement of atoms or molecules or ions which constitute the crystals. Some examples of crystalline solids are sodium chloride, sugar, alum and diamond. A crystal of sodium chloride is cubic. In sodium chloride, Na + and Cl– ions are arranged in the crystal lattice at alternate sites. Each Na + is surrounded octahedrally by six Cl– ions and each Cl– is surrounded octahedrally by six Na+ ions. This arrangement exists throughout the crystal. There are some crystalline solids whose crystalline structure contains few molecules of water. Such crystals are called hydrates. The water of hydration is called water of crystallisation. Examples of such crystalline solids are Blue vitriol (CuSO 4. 5H2O), Green vitriol (FeSO4. 7H2O), Glauber's salt (Na2SO4. 10H2O), White vitriol (ZnSO4. 7H2O), Washing soda (Na2CO3.10 H2O). There are some crystalline solids which do not contain water of crystallisation. Such salts are called anhydrous. Some examples of such salts are sodium chloride (NaCl), potassium nitrate (KNO3), ammonium chloride (NH4Cl) etc. Amorphous solids : Amorphous solids are rigid and incompressible and possess some ordered arrangement around a particular atom or ion which lasts only upto short distances. Examples of such solids are glass, fused silica, rubber and plastic. DISTINCTION BETWEEN CRYSTALLINE AND AMORPHOUS SOLIDS Crystalline Amorphous 1. Geometry : Crystalline solids have 1. Amorphous solids do not have regular regular and definite geometry which geometry. The ordered arrangement extends throughout the crystal. extends only upto a short distance. 2. Melting point :Crystalline solids 2. Amorphous solids do not possess sharp possess sharp melting points. melting points. 3. Isotropy and Anisotropy : Crystalline 3. Amorphous solids are isotropic i.e. solids are anisotropic i.e. their physical their physical properties such as properties such as conductivity, conductivity, refractive index are the refractive index etc. are different along same along all directions. different directions. 4. Cleavage : When a crystalline solid is 4. When an amorphous solid is cut with a cut with a sharp edged tool, it is readily sharp edged tool, it gives smaller pieces cut into smaller crystals with plane with irregular surfaces. surface. 5. Symmetry : Crystalline solids possess 5. Amorphous solids do not possess crystal symmetry. symmetry. THE SOLID STATE 3 Classification of Crystalline solids : Crystalline solids may be further classified into following types according to the nature of particles constituting them and the binding forces between them. a. Ionic solids. b. Covalent solids. c. Molecular solids. d. Metallic solids. a. Ionic solids : In ionic solids, the constituent particles are ions which are held together by electrostatic forces. The arrangement of these ions is such that cations have an ions as their nearest neighbours and vice versa. Examples of ionic solids are salts like Sodium chloride (NaCl), Lithium fluoride (LiF), Barium sulphate (BaSO 4), Sodium nitrate (NaNO3), Sodium sulphate (Na2SO4) etc. Fig. 1.1 Sodium chloride crystal Because of stronger and non-directional electrostatic interactions the ionic solids are hard, brittle, and possess high melting and boiling points. They are bad conductors in the solid state but good conductors in the molten state. b. Covalent solids : In covalent solids the constituent particles are the atoms which are held by covalent bonds. The bonds in covalent solids extend throughout the crystal and this results in the formation of a giant three dimensional structure. Some examples of covalent solids are diamond, graphite, quartz (SiO 2). Covalent solids are hard, non- volatile and possess high melting points. They are bad conductors of heat and electricity. c. Metallic solids : In metallic solids, the constituent particles are positive ions immersed in a sea of electrons. The positively charged metal ions are held together by the cloud of negative electrons. The cloud of electrons belong to the entire net work of crystals. Some examples of metallic solids are common metals like copper, silver, aluminium and sodium and some alloys. Metallic solids are malleable and ductile. They have metallic lustre and are good conductors of heat and electricity. d. Molecular solids : In molecular solids, the constituent particles are small molecules which are held together by weak van der Waals forces. Some examples of molecular solids are solid carbon dioxide, ice, sugar, iodine etc. Molecular solids are soft and volatile. They possess low melting points and are bad conductors. 4 +2 CHEMISTRY (VOL. - II) 1.3 CRYSTAL LATTICES AND UNIT CELLS : Crystal lattice : A crystal lattice (or space lattice) is a general term of an arrangement of points in space representing the atoms, ions or molecules forming the crystal which if extended in all directions throughout the crystal forms a repeating unit giving a shape of the crystal. In otherwords, a crystal lattice is a regular arrangement of the constituent particles (atoms, ions or molecules) of a crystalline solid in three dimensional space. Lattice points : The positions which are occupied by the atoms, ions or molecules in the crystal lattice are called lattice points or lattice sites. Unit cell : It is the smallest repeating unit in crystal lattice which when repeated over and over again produces the complete crystal lattice. Such units are repeated over and over again in three dimensions and represents the shape of the entire crystal. The collection of points in the unit cell indicate the crystal coordination number and are in consistence with the formula of the compound. space lattice UNIT CELL Fig. 1.2 Space lattice and a unit cell Close packing in Crystalline solids : In the formation of crystals the constituent particles (atoms, ions or molecules) get closely packed together. The closely packed arrangement is that in which the maximum available space is occupied. The closer the packing, the greater is the stability of the packed system. The packing will also vary according to the shape and size of the constituent particles of crystals. THE SOLID STATE 5 (i) Close packing in two dimensions : To understand the packing of constituent particles let us consider the packing of hard spheres of equal size. The spheres can be arranged side by side touching each other in a row. The rows can be combined in the following two ways with respect to the first row to build a crystal plane. 1. The spheres are packed in such a way that the rows have a horizontal as well as vertical alignment. In this arrangement the spheres are found to form squares. This type of packing is also called square close packing. (scp) 2. The spheres are packed in such a way that the spheres in the second row are placed in the depressions between the spheres of the first row. Similarly, the spheres in the third row are placed in the depressions between the spheres of the second row and so on. This gives rise to hexagonal close packing of spheres (hcp) A B Fig 1.3 (A) A sphere in square close packing is in contact with four spheres. (B) A sphere in hexagonal close packing is in contact with six spheres. Arrangement I Arrangement II (Less closely packed) (More closely packed) Fig. 1.4 Packing of Spheres (ii) Close packing in three dimensions : — A Layer a a a a a b b b b —B Layer a a b b b Fig. 1.5 Packing of second layer (B) on first layer (A) 6 +2 CHEMISTRY (VOL. - II) Consider the above arrangement. Let us mark the spheres in the first layer as A. It is clear from the above arrangement that there are two types of voids of hollows in the first layer. These are marked as a and b. All the hollows are equivalent but the spheres of second layer may be placed either on hollows which are marked 'a' or on other set of hollows marked 'b'. It is to be noted that it is not possible to place spheres on both type of hollows. Let us place the spheres on hollows marked 'b' to make the second layer which may be labelled as B layer. Obviously the holes marked 'a' remain unoccupied while building the second layer. The second layer is indicated as dotted circles. When a third layer is to be added, again there are two types of hollows available. One type of hollows marked 'a' are unoccupied hollows of first layer. The other type of hollows are hollows in the second layer marked 'c'. Thus two alternatives are available to build the third layer. 1. In this case, the spheres of the third layer lie directly above those in the first layer. This type of packing is referred to as ABABA....... arrangement. A B A (a) (b) Fig. 1.6 ABABA... or hcp arrangement of spheres. It is also known as hexagonal close packing (hcp) 2. The second way to pack spheres in the third layer is to place them over hollows marked 'a'. This gives rise to a new layer labelled as 'C'. However it can be shown that the spheres in the fourth layer will correspond to those in the first layer. This gives rise to A B C A B C A........type of arrangement. It also known as cubic close packing. (ccp). A A C C B B A (a) (b) (c) Fig. 1.7 ABCABCA... or ccp arrangement of spheres. THE SOLID STATE 7 1.4 TYPES OF CUBIC CRYSTALS : It is a fact that cubic system is the simplest system. There are three common types of cubic system. 1. Simple cubic. 2. Body centred cubic (bcc) 3. Face centred cubic (fcc) or Cubic close packing (ccp) 1. Simple cubic : In this arrangement the points (atoms, ions or molecules) are present at all the corners of a cube. 1 Simple cubic 8 atom Fig. 1.8 Simple cubic arrangement and number of spheres per unit cell. From the figure it is clear that the atom present at each corner contributes 81 to each cube because it is shared by 8 cubes. Now there are 8 atoms at the corners. Thus the number of atoms present in each unit cell = 8 corner atoms x 81 atoms per unit cell = 1 atom. 2. Body centred cube (bcc) : It has points at all the corners as well as at the centre of the cube. 1 8 atom 1 atom (a) (b) Fig. 1.9 Body centred cubic arrangement. It is clear from the figure that there are eight atoms at the corners and each is shared by 8 unit cells so that the contribution of each atom at corner is 81. In addition there is one atom in the body of the cube which is not shared by any other cube. 8 +2 CHEMISTRY (VOL. - II) Therefore, the number of atoms present at the corners per unit cell = 8 corner atoms x 81 atom per unit cell = 1 The number of atoms present at the centre of the cube = 1 \ Total number of atoms in bcc arrangement = 1 + 1 = 2. Thus, a body centred cube has two atoms per unit cell. 3. Face centred cube (fcc). This is also called cubic close packed arrangement. It has points at all the corners as well as at the centre of each of the six faces. 1 (a) (b) 8 atom Fig. 1.10 Cubic close packed or face centred cubic arrangement and share of each atom per unit cell. In this arrangement, there is one atom at each of the eight corners. From the above figure it is quite clear that atom present at each corner contributes 81 to each cube because it is shared by 8 cubes. In addition, there are six atoms at the faces of the cube and each is shared by two unit cells. Therefore the contribution of each atom at the face per unit cell is 21. \ The number of atoms present at corner per unit cell = 8 corner atoms x 81 atoms per unit cell =1 The no. of atoms present at faces per unit cell = 6 atoms at faces x 21 atoms per unit cell = 3 \The total no of atoms in ccp or fcc arrangement = 1 + 3 = 4 The following table (1.1) depicts the total no. of atoms present per unit cell in different types of crystals. Table 1.1 No. of atoms per unit cell in different crystals Unit cell No. of No. of atoms No. of Total No. atoms at corners at faces atoms in centre of atoms 1 Simple cubic 8x 8 0 0 1 1 Body centred 8x 8 0 1 2 1 1 Face centred 8x 8 6x 2 0 4 THE SOLID STATE 9 1.5 CALCULATION OF DENSITY OF UNIT CELLS : The density of unit cell can be calculated knowing the type of crystal structure and the edge length of the unit cell. Let the edge length of unit cell = x pm Volume of unit cell = (x pm)3 = (x × 10–10 cm)3 = x3 × 10–30 cm3 Mass of unit cell Density of unit cell = Volume of unit cell No. of atoms in the unit cell× Mass of each atom = Volume of unit cell n× M N x × 10 30 cm3 3 nM 3 = g. cm Nx 3 10 30 where n = No. of atoms in the unit cell M = Atomic mass N = Avogadro Number Thus, knowing the density of unit cell, the atomic mass as well as number of atoms or Avogadro number can be determined. n = 1, 2, and 4 for simple cubic lattice, bcc and fcc lattice respectively. 1.6 INTERSTICES OR INTERSTITIAL VOIDS : In close packing spheres, certain hollows are left vacant. These hollows or voids in the crystals are called interstital sites, or interstitial voids or simply interstices. Two such voids are quite important. 1. Tetrahedral 2. Octahedral. 1. Tetrahedral void : Tetrahedral hole Tetrahedral hole Fig. 1.11 Tetrahedral void. 10 +2 CHEMISTRY (VOL. - II) The above arrangement of four spheres shows that their centres lie at the apices of a tetrahedron. But the shape of the void is not tetrahedral. Thus the vacant space among four spheres having tetrahedral arrangement is called tetrahedral site or tetrahedral hole. 2. Octahedral void : Octahedral hole Octahedral hole Octahedral hole Fig. 1.12 Octahedral site This type of void is formed at the centre of six spheres. In the above arrangement, each octahedral site is produced by two sets of equilateral triangles which point in opposite directions. Thus the void formed by two equilateral triangles with apices in opposite direction is called octahedral site or octahedral hole or simply octahedral void. This site is therefore surrounded by six spheres lying at the vertices of a regular octahedron. 1.7 CO-ORDINATION NUMBER : The number of nearest neighbours with which a given sphere is in contact is called co-ordination number. For ionic solids, the ratio of the radius of cation to that of anion is called radius ratio. The radius ratio for a given co-ordination number is fixed. To understand it better, let us consider ionic solids. Each ionic solid is made up of cations and anions which have definite arrangements. Each ion is surrounded by a number of ions of opposite charge. For example, in A+B–, A+ ions are surrounded by a definite number of B– ions. This number is called co-ordination number of A +. Similarly, the number of A+ions which are surrounding a B– ion is called co-ordination number of B– ions. Since the arrangement of ions in a crystal and the co-ordination number of ions depend upon the ratio of its radius with respect to the radius of the ions or atoms surrounding it, the radius ratio can be represented as : + Radius ratio = Radius of the cation Radius of the anion = r r - Radius ratio plays very important role in determining the structures of ionic solids. We know that the cations and anions in the ionic compound are held together by strong electrostatic forces. As a result, the ions try to arrange themselves in such geometrical arrangements where the attractions between the oppositely charged ions are maximum and the repulsions between the similar charged ions are minimum. Example - Consider an ionic crystal AB in which a cation is surrounded octahedrally by six anions. For simplification, let us take any four B – ions. There will be two more B– ions, one above and the other below A+ ion which have been omitted for clarity. The most stable arrangement is one in which anions are touching each other and the cation simultaneously. THE SOLID STATE 11 (a) O Anion (b) l Cation (c) Fig. 1.13 Effect of change of size of anion (same cation) and the stability of structure. The cation is octahedrally surrounded by six anions but only four are shown. The anions above and below the cation are not shown for simplicity. This arrangement will be most stable. However, if the size of the anion is less (cation same) the anions will no longer touch other anions and the structure will be unstable. (a) s ease r +/r – – decr inc r+ /r rea ses (b) (c) r+ = 0.414 – 0.732 r- –Octahedral C.N. increases from 6 to 8 Cubic + + ( rr - > 0.732) C.N. decreases from 6 to 4 Tetrahedral ( rr - < 0. 414 ) Fig 1.14 Effect of radius ratio on co-ordination number. Similarly, if the size of anions is large (cation same) all the anions will not be able to touch the cation simultaneously. The structure will be unstable. Therefore, if we decrease or increase the radius of the anion, keeping the cation same, the co-ordination number may increase or decrease to get stable arrangement. This means that the co-ordination number of a compound depends upon the radius of the cations and anions. Radius ratio versus possible co-ordination number : The possible + co-ordination numbers and structural arrangements of anions around cations r for different r - values are given below in table 1.2. Table 1.2 Radius ratio versus co-ordination number with examples Radius ratio Possible Structural Examples Co-ordination number arrangement 0.155 – 0.225 3 Trigonal planar B2O3 0.225 – 0.414 4 Tetrahedral ZnS, SiO44– 0.414 – 0.732 6 Octahedral NaCl 0.732 – 1.0 8 Cubic CsCl 12 +2 CHEMISTRY (VOL. - II) Example : The radius of Na+ ion is 95 pm and that of Cl– ion is 181 pm. Predict whether the co-ordination number of Na+ ion is 6 or 4. (pm = picometer = 10–12m) Solution : Radius of Na+ = 95 pm Radius of Cl– = 181 pm. r+ r + (Na + ) 95 Radius ratio , r - = = 181 = 0.524 r - (Cl - ) The radius ratio lies between 0.414 – 0.732. Hence, Na+ ions prefer to occupy octahedral holes having co-ordination number 6. Structure of substances related to close packed lattices : Example : 1. Structure of sodium chloride : A unit cell representation of sodium chloride is shown in fig. 1.15 Cl– Na+ Cl– ion octahedrally surrounded by six Na+ ions Na+ ion octahedrally surrounded by six Cl – ions Fig. 1.15 Representation of unit cell of NaCl. The salient features of the structure are : i. The Cl– ions adopt cubic close packed arrangement. Therefore, Cl – ions are present at all the corners and at the centre of each face of the cube. This arrangement is also regarded as fcc arrangement of Cl – ions. ii. The Na+ ions occupy all the octahedral sites. iii. Since there is an octahedral site per atom in closed packed arrangement, there will be one Na+ ion for every Cl– ion. Thus the ratio of Na+ and Cl– ions in this structure is 1 : 1 and the formula of the compound is Na + Cl–. iv. In this structure, each Na+ ion is surrounded by 6 Cl– ions which are disposed towards the corners of a regular octahedron. (Fig 1.16 ). Similarly each Cl – ion is surrounded by six Na+ ions. Thus the co-ordination numbers of Na+ and Cl– in NaCl structure are 6 and 6. THE SOLID STATE 13 2. Structure of Zinc sulphide (Zinc blend) Zn2+ion tetrahedrally surrounded by S2–ion four S2– ions tetrahedrally surrounded by four Zn2+ ions Zn2+ion of second unit cell Fig. 1.16 Representation of zinc blend (ZnS) structure. The salient features of the structure are : i. The S2– ions form cubic close packed arrangement. In this arrangement the S 2– ions are present at the corners of the cube and at the centre of each face. ii. The zinc ions (Zn2+) occupy half of the tetrahedral sites. iii. There are two tetrahedral sites per atom in a closed packed lattice. That means there are two tetrahedral sites available for every S 2– ions. In this arrangement, any half of the tetrahedral sites is occupied by Zn 2+ ions. Therefore, there is one Zn2+ ion for every S2– ion and the formula is ZnS. iv. In this structure each Zn2+ ions is surrounded by four sulphide ions which are disposed towards the corner of a regular tetrahedron. Similarly each S 2– ion is surrounded by four Zn2+ ions which are also disposed towards the corners of a regular tetrahedron. 3. Structure of CaF2 (Calcium fluoride) : F– ion surrounded by 4 Ca2+ ions F– Ca2+ Fig. 1.17 Representation of CaF 2 structure. The salient features of the structure are : i. The Ca2+ ions are arranged in ccp arrangement. In this arrangement Ca 2+ ions are present at all the corners and at the centre of each face of the cube. ii. The fluoride ions occupy all the tetrahedral sites. 14 +2 CHEMISTRY (VOL. - II) iii. There are two tetrahedral sites per atom in a closed packed lattice. This means there are two tetrahedral sites for every Ca 2+ ion. Since F– ions occupy all the tetrahedral sites, there will be two F – ions for each Ca2+ ion. Thus the formula of the substance is CaF2. iv. In this structure, each F– ion is surrounded by four Ca2+ ions, while each Ca2+ ion is surrounded by eight F– ions. Thus the co-ordination numbers of Ca2+ & F– ions are 8 & 4. 4. Structure of Cesium chloride (CsCl) Cs+ ion Cl– surrounded by 8 Cs+ Cl– ions (a) (b) Cl– ion surrounded by 8 Cs+ ions Fig. 1.18 Representation of CsCl structure. The salient features are : i. The Cl– ions are arranged in a simple cubic arrangement. In this arrangement the Cl– ions are present at all the cornes of the cube. ii. The Cs+ ions occupy the cubic site. That is Cs+ ions are present at the body centre of the cube. iii. From the above figure, it is clear that there are 8 Cl – ions at the corners of the cube. Since each ion at the corner is shared by eight unit cells, its contribution per unit cell is 1/8. Therefore 8 Cl– ions at the corners = 8 x 1 = 1 Cl– ion per unit cell. 8 There is also one Cs+ ion in the body centre and its contribution per unit cell is 1. Thus there is one Cl– for each Cs+ ion and the compound has the formula CsCl. iv. In this structure, each Cs+ ion is surrounded by 8 Cl– ions which are disposed towards the corners of a cube. (see the fig. 1.18) When the unit cell is extended, it can be seen that each Cl– ion is also surrounded by 8 Cs+ ions. Thus, the co-ordination number of Cs+ and Cl– ions are 8 and 8. 1.8 POINT DEFECTS : The crystal which is made up of same unit cells and contains the same lattice points throughout the crystal is said to be an ideally perfect crystal. Any deviation of the ideally perfect crystal from the periodic arrangement of its constituents is known as defect or imperfection of the crystal. THE SOLID STATE 15 The imperfection or defect which arises due to missing atoms, displaced atom or extra atom within the crystals in known as Point defect. Point defects are thus due to imperfect pack- ing during original crystallisation or they may arise due to thermal vibration of atoms at elevated temperature. The common point defects one Schotty defect and Frenkel defect. The less com- mon point defects includes metal excess defect and metal deficiency defects. Defects in stoichiometric solids - Stoichiometric compounds are those in which the number of +ve and –ve ions are in the same ratio as indicated by their chemical formulae. The defects which do not disturb the stoichiometry of the compound are known as stoichiometric defects. These are of the following types. (1) Schottky Defects (i) These defects arise due to missing of equivalent number of cations and anions from their respective positions in the crystal lattice thereby forming pair of holes. (ii) These defects are more common in ionic compounds with high co-ordination number and having both positive and negative ions with almost equal size. (iii) The crystal, as a whole, is electrically neutral since the number of missing +ve and –ve ions is the same. (iv) Examples of ionic crystal showing Schottky defect include NaCl, KCl, KBr, CsCl etc. X+ Y X+ Y X+ + Y X Y X+ Y X+ Y Y X+ Y X+ Fig. 1.19 Schottky Defect Consequences of Schottky defects. (i) Due to Schottky defect there is an increase in volume of the crystal with no in- crease in mass. (ii) The density as well as the covalent character of the crystalline solid decreases. (iii) The crystal becomes capable of conducting a small amount of electricity through ion jump mechanism. (iv) The movement of atoms or ions in the crystal is induced due to existence of a vacancies. This accounts for the phenomenon of diffusion solids. (v) The number of Schottky defects increase with increase in temperature. (vi) The lattice energy of the crystal in lowered due to presence of holes. Thus, stability of crystal is lowered. 16 +2 CHEMISTRY (VOL. - II) (2) Frenkel Defects (i) This defect arises due to shifting of an ion from its normal position to interstitial site in the crystal lattice between the lattice points thereby causing a vacancy in the original position. (ii) This defect is more common in ionic compounds having low co-ordination number and having large difference in size between positive and negative ions. (iii) The crystal remains neutral since the number of +ve ions is equal to the number of –ve ions. (iv) In an ionic crystal generally the cation moves since it is smaller than the anion and can easily fit into the vacant space in the lattice. (v) Examples of ionic crystals showing Frenkel defect include ZnS, AgCl, AgBr, AgI etc. X+ Y X+ Y Y X X+ Y- X X Y- X Y Y X Y X Fig. 1.20 Frenkel Defect Consequences of Frenkel Defects (i) The crystals are made good electrical conductors due to these defects. (ii) These defects also account for the phenomenon of diffusion in solids. (iii) These defects bring about closeness of similar charges which tend to increase the dielectric constant of the crystal. (iv) The number of Frenkel defects increase with temperature. (v) The stability of the crystal is lowered due to presence of the holes. Defects in Non-stoichiometric solids Non-stoichiometric solids are those in which the ratio of +ve and –ve ions differs from that represented by chemical formulae. These compounds do not strictly obey the law of constant proportions. Examples include Feo.94 O or VOx , where x is between 0.6. and 1.3, In such type of compounds the balance of +ve and –ve charge is made by having either extra electrons or extra +ve charge. As a result the crystal structure becomes irregular and defective. These defects are of two types. THE SOLID STATE 17 (i) Metal excess defects When the metal ions are in excess as compared to –vely charged ion, the solid is said to have metal excess effect. There defect are due to two phenomena. (a) Anion vacancies (i) This defect arises due to removal of anions or nonmetal ions from the lattice sites resulting in the increase in concentration of metal ion or cation. (ii) The vacancy caused by the loss of anion is occupied by electron so that electrical neutrality is maintained X Y X Y Y X e X X Y X Y Y X Y X Fig. 1.21 Metal excess defect (iii) This type of defect is observed in crystals which are likely to exhibit Schottky defect. Alkali metal halides are heated in a medium of alkali metal vapour so that anion vacancies are created. Alkali metals get deposited over alkal halide crystal. The halide ions move towards the surface and combine with metal ions. (iv) On the otherhand when metals are converted into metal ions electrons are pro- duced and the electron diffuse into the crystal and occupy the vacant positions in the lattice sites. (v) The electrons occupy the holes known as F- Centres or Coloured centres (German word ‘Farbe’ meaning colour). F-centre is responsible for colour of the compound. For example, NaCl is yellow due to presence of excess Na+ ion. KCl is violet due to presence of excess K+ ion. Consequences of Metal excess deffect due to anion vacancies (a) The solids havings metal excess deffect act as semiconductors. This is due to pres- ence of electrons at the F-centres. (b) The electrons present at F- centres are excited to higher energy level and when they return to the ground state they do so by emitting certain radiation. This radiation falls is the visible region, so a colour is visualised. For example, ZnO gets yellow on heating. (c) The solids having F-centres with unpaired electrons are paramagnetic. 18 +2 CHEMISTRY (VOL. - II) (b) Extra cations in interstitial sites. (i) This defect arises due to presence of extra cations in the interstitial sites. (ii) To maintain electrical neutrality equivalent number of electrons are placed in the interstital sites. Fig. 1.22 Metal excess defect due to interstitial cations. (iii) This type of defect is observed by the crystals which are likely to exhibit Frenkel defect. For example, when ZnO is heated, oxygen is lost reversibly and the intersti- tial sites accomodate excess metal ion. The electrons are trapped in the neighbourhood. (iv) The electrical conductivity and the yellow colour in hot condition are due to these trapped electrons. 2. Metal deficiency defect If the number of metal ions is less than the number of –vely charged ions, the solid is said to have metal deficiency defect. These defects are of two types. (a) Cation vacancies (i) This arises due to loss of cations from normal lattice site. (ii) When a cation is missing, an extra electron must be present in the crystal and the extra negative charge in balanced by neighbouring metal ion (X +) acquiring two +ve charges (X++) instead of one. Fig. 1.23 Metal deficiency defect due to cation vacancy THE SOLID STATE 19 (iii) The movement of +ve hole is caused due to apparent movement of X 2+ ions is due to movement of an electron from X+ ion. (iv) Transition metal compounds having metals with variable valencies exhibit this type of defect. Some specific examples are crystals of FeO, NiO and FeS. (b) Extra anions in the interstitial sites (i) This effect arises due to presence of extra anions in the interstial spaces of the crystal. (ii) The cations carrying additional charge are helpful in maintaining electrical neutrality. (iii) Anions are much larger than cation therefore do not fit well into interstitial sites. Hence this defect is usually not seen. 1.9 ELECTRIC AND MAGNETIC PROPERTIES OF METALS : Metals conduct electricity due to the movement of electrons or ions when a potential difference is created. The conduct of electricity by metals takes place in solid as well as in molten state. The conductivity of metals depends upon the number of valence electrons present in it and the binding energy. The atomic orbitals of atoms linearly overlap to form molecular orbitals which are very close to each other in energy to form a band. If this band is partially filled in it overlaps with a higher energy unoccupied conduction band, then electrons can flow easily under an applied electric field and metal behaves as good conductor. (Fig. 1.24a) If the energy gap between filled valence band and the next higher unoccupied band is large, electrons cannot jump to the unoccupied band. Such a substance cannot conduct electricity and behaves as insulator. (Fig. 1.24b) When the energy gap between the filled valence band and the next higher unoccupied band is small, some electrons can jump to the conduction band and show some conductivity, such substances are called semiconductors. Electrical conductivity of semiconductors increases with the rise of temprerature because electrons acquire more energy and can jump to the conduction band. Substances like silicon and germanium show this type of behaviour and are called intrinsic semiconductors. The conductivity of these intrinsic semiconductors is too low to be of practical use. Their conductivity is increased by adding an appropriate amount of suitable impurity. This process is called doping. Empty band Empty band.................................. Forbidden zone.................................. Small energy gap................. (Large energy gap) Energy Filled band Partially Overlapping filled band bands (a) Metal (b) Insulator (c) Semiconductor Fig. 1.24 Electronic Bands of (a) Metal (b) Insulator and (C) Semiconductor 20 +2 CHEMISTRY (VOL. - II) Such substances are called extrinsic or impurity semiconductors. Depending on the nature of impurity added extrinsic semiconductros are of two types : (a) n-type extrinsic semiconductors and p-type extrinsic semiconductors. (a) n-Type extrinsic semiconductors : These are obtained by adding impurity atoms having more external electrons than the parent insulator atoms. Silicon and Germanium are insulators which belong to group 14 of the periodic table and have four valence electrons each. When phophorous, arsenic and antimony (all containing five valence electrons) atoms are added to pure silicon or germanium, we get n-type extrinsic semiconductors. Each of these atoms occupy some of lattice stites in silicon or germanium crystal. Four out of five electrons are engaged in formation of four covalent bonds with the four neighbouring silicon atoms. The fifth extra electron is free to occupy the lattice points. Such extra electrons occupy delocalised level, called donor impurity level which remains just below the empty conduction band of silicon or germanium crystal. These extra electrons can easily be excited to the empty conduction band by the application of electric field or by increase in the thermal energy. Thus silicon or germanium become semiconductors by doping. Here the increase of conductivity is due to the negatively charged electron of the electron-rich impurity, hence the name n-type semiconductor. (Fig. 1.25a) Empty Empty conduction conduction band band Acceptor impurity e e e e e level containing Donor impurity Energy positive holes containing extra electron ÅÅÅÅÅ Filled conduction Filled valence band band (a) n-type semiconductor (b) p-type semiconductor Fig. 1.25 (a) n-type semiconductor, (b) p-type semiconductor (b) p-Type semiconductors : These are obtained when an impurity atom to be added has fewer external electrons than the parent insulator atoms. Silicon or Germanium can also be doped with a group 13 element like boron, aluminium or gallium which contains only three valence electrons. The place where the fourth valence electron is missing is called electron hole or electron vacancy. This electron vacancy creates a positive hole in the valence band of silicon or germanium. THE SOLID STATE 21 There are as many positive holes as there are impurity atoms. These positive holes occupy the level, called acceptor impurity level which exists close to the filled valence band of the acceptor crystal. Electrons from the filled valence band can thermally be promoted to this empty acceptor impurity level of positive holes. Under the influence of an applied potential an electron from an adjacent atom moves into the hole and in turn is replaced by an electron from another atom. In this way the molecule move across the crystal in a direction which is opposite the direction of electron migration. The conduction takes place due to the migration of the positive holes. Hence the name p-type is given to these extrinsic semiconductors. (Fig. 1.25b) Various combination of n-type and p-type semiconductors are used for making electronic components. Diode is a combination of n-type and p-type semiconductors and is used as rectifier. Transistors are made by placing one type of semiconductor between two other type, such as npn or pnp semiconductors. These are used to detect or amplify radio or audio signals. Solar cell is an efficient photodiode used for coversion of light energy into electrical energy. Magnetic properties of solids : Magnetic properties of solids generate due to the movement of electrons in an atom. An electron has two types of motion (i) revolution around the nucleus and (ii) spinning along its own axis. Since electron is a charged body its movement generates magnetic field. It behaves like a tiny bar magnet and possesses magnetic moment. The magnitude of the magnetic moment is very small and is measured in the unit called Bohr magneton. It is equal to 9.27 × 10–24 Am2. On the basis of the magnetic properties, substances can be classified into five categories : (a) paramagnetic (b) diamagnetic (c) ferromagnetic (d) anti-ferromagnetic and (e) ferrimagnetic. (a) Paramagnetism : Paramagnetism is due to presence of unpaired electrons which are attracted by the magnetic field. They are magnetised in a magnetic field in the same direction and lose their magnetism in the absence of the field. Some examples of paramagnetic substances are O 2, Cu2+, Fe3+, Cr3+ etc. (b) Diamagnetism : Diamagnetism is due to the presence of all paired electrons in a substance. These substances are weakly repelled by magnetic field. H 2O, NaCl and benzene are some examples of such substances. They are weekly magnetised in a magnetic field in opposite direction. Pairing of electrons cancels their magnetic moment and they lose their magnetic character. (c) Ferromagnetism : Ferromagnetic substances are strongly attracted by magnetic field. Besides strongly attracted these substances can be permanently magnetised. In solid state, the metal ions of ferromagnetic substances are grouped together in small regions called domains which act as tiny magnets. In an unmagnetised ferromagnetic substance these domains remain randomly oriented and their magnetic moments are cancelled. When the substance is placed in a magnetic 22 +2 CHEMISTRY (VOL. - II) field all the domains get oriented along the direction of the magnetic field and a strong magnetic effect is produced. This order of the domains remains as such even after the magnetic field is withdrawn and the ferromagnetic substance becomes permanently magnetic. Iron, cobalt, nickel, gadolinium and CrO 2 are examples of ferromagnetic substances. (d) Anti-ferromagnetism : Substances like MnO have their magnetic domain structure similar to ferromagnetic substances, but their domains are oppositely oriented and cancel out each others magnetic moment. (e) Ferrimagnetism : Ferrimagnetism is observed when the magnetic moments of the domains in the substance are alligned in parallel and anti-parallel directions in unequal numbers. They are weakly attracted by magnetic field as compared to ferromagnetic substances. Magnetite (Fe3O4) is such a substance. These substances lose ferrimagnetism on heating and become paramagnetic. (a) Ferromagnetic (b) Anti-ferromagnetic (c) Ferrimagnetic CHAPTER (1) AT A GLANCE 1. Solids are characterised by definite shape, definite volume and fixed melting point. Compressibility, rigidity, high mechanical strength are the properties of a solid. 2. Solids are classified as crystalline and amorphous solids. 3. Crystalline solids have definite geometry, sharp melting point and crystal symmetry. They are anisotropic an nature. 4. Amorphous solids have neither definite geometry nor sharp melting point. They do not possess symmetry and are isotropic in nature. 5. Crystalline solids are classified as ionic, covalent, molecular and metallic solids. 6. Ionic solids are hard, brittle, possess high melting point. Covalent solids are hard, nonvolatile, bad conductors of heat and electricity. Metallic solids are malleable and ductile, have metallic lusture and are good conductors. Molecular solids are soft and volatile and bad conductors. 7. A crystal lattice is regular arrangement of the constituent particles (atoms, ions or molecules) of a crystalline solid in three dimensional space. 8. The positions that are occupied by the atoms, ions or molecules in the crystal lattice are called lattice points or lattice sites. 9. Unit cell is the smallest repeating unit in crystal lattice which when repeated over and over again produces the complete crystal lattice. THE SOLID STATE 23 10. Close packing in two dimensions in crystalline solids may be square close packing (scp) or hexagonal close packing (hcp). 11. In three dimension close packing ABABA... arrangement is known as Hexagonal Close Packing (hcp), whereas ABCABCA... is known as Cubic Close Packing (ccp) 12. There are three common types of cubic systams. They are Simple Cubic, Body Centred Cubic (bcc) and Face Centred Cubic (fcc). 13. The no. of atoms per unit cell in simple cubic, body centred cubic and face centred cubic crystals are 1, 2 and 4 respectively. 14. The hollows or voids in the crystal are known as interstitial voids. These voids may be tetrahedral or octahedral. 15. The number of nearest neighbours with which a given sphere is in contact is known as the co-ordination number. 16. Radius ratio = Radius of cation Radius of anion 17. On the basis of electrical conductivity, solids are divided into three categories : (i) Metals (ii) Insulators (iii) Semiconductors. Free electrons in the metals are responsible for conduction of electricity. Conductivity of semiconductors is intermediate between metals and insulators. Semiconductors are of two types : Intrinsic and Extrinsic. Extrinsic semiconductors are either n-type or p-type. Their combinations are used in making electronic components. 18. On the basis of magnetic properties, solids are classified into five categories : Paramagnetic, Diamagnetic, Ferromagnetic, Anti-ferromagnetic and Ferrimagnetic. QUESTIONS A. Very short answer type (One mark each) : 1. Diamond and graphite are —————. (allotropes, isomorphous) 2. Diamond is ————— solid. (co-valent, ionic, molecular) 3. What is the number of atoms present per unit cell in a face centred cubic and a body centred cubic arrangement. 4. What is the radius ratio for an ion to occupy tetrahedral site. 5. Explain isotropy. 6. Define Anisotropy. 7. Define a unit cell of a crystal. 8. What are interstitials ? 9. What are the types of lattice imperfections found in crystals ? 24 +2 CHEMISTRY (VOL. - II) 10. What do you mean by crystal lattice ? 11. How many types of close packing are known in crystals ? 12. Define co-ordination number of a crystal. 13. Explain interstitial voids. 14. How many types of lattice points occur in diffrent cubic unit cells ? 15. What is the number of atoms in a body centred cubic unit cell of a monoatomic substance ? 16. What is a polycrystalline solid ? 17. What are crystallites ? 18. Calculate the number of atoms contained in body centred cubic cell. 19. Give two examples of ionic solids. 20. Diamond, Graphite and Quartz are ————— solids. 21. Define metallic solids. 22. What is meant by molecular solids ? 23. What is meant by radius ratio ? 24. Why carbon tetrachloride is immiscible in water ? 25. The solubiltiy of a solid ————— by increase of pressure. (increased, not changed, decreased) 26. What is the effect of pressure on the solubility of a solid ? 27. What happens to the solubility of calcium acetate if temperature increases 28. Give two examples of molecular solid. 29. Give an example of hcp and bcc crystals. 30. What is the commercial name of SiC ? 31. What are the coordination numbers of Cs+ & Cl– in CsCl lattice ? B. Short Answer Type (Two marks each) : 1. Give two points of difference to distinguish between crystalline and amorphous solids. 2. If the radii of the cation and anion are 95 pm and 181 pm respectively, what would be coordination number and the type of crystal geometry? 3. Explain how hcp or ccp for the some element give the same identity? 4. What should be the ideal radius of the anion in a NaCl type of structure if the radius of the cation is r ? + 5. Calculate the radius ratio rr– and the condition number of Li+ and F– in LiF crystal from the given data rLi+ = 60 pm and rF– = 136 pm. 6. Silver crystallises in fcc lattice with all the atoms at the lattice points. The length of the edge of the unit cell as determined by x-ray diffraction studies is found 408.6 pm. the density of silver is 10.5g cm–3. Calculate the atomic mass of silver. THE SOLID STATE 25 7. Explain the difference between conductor and insulator. 8. Explain the difference between conductor and semiconductor. 9. Explain the following : (i) Ferromagnetism (ii) Paramagnetism (iii) Antiferromagnetism (iv) Ferrimagnetism 10. What are interstitials and interstitial voids ? C. Short answer type (Three marks each) : 1. Write four important characteristics of solids. 2. Write two points to distinguish between Crystalline and Amorphous solids. 3. What are chief characteristics of ionic crystals ? 4. Describe a few general characteristics of covalent crystals. 5. What are molecular crystals ? How many types of molecular crystals are known ? 6. Explain metallic crystals and their properties ? 7. What do you understand by the terms space lattice and unit cell. ? 8. Define co-ordination number in crystals. Is the co-ordination number of a sphere in ccp and hcp arrangement same or different ? 9. Discuss the following types of cubic structures : a. Simple cubic b. Body centred cubic. c. Face centred cubic. 10. How does radius ratio help in determining the structures of compounds ? 11. What are interstitial sites ? Discuss tetrahedral and octahedral interstitial sites in a closed packed arrangement. 12. Explain why diamond is hard while graphite is soft. D. Long answer type (Seven marks each) : 1. Describe various characteristics of solids. 2. What do you understand by close packing of spheres ? Discuss briefly hexagonal close packing and cubic close packing of spheres. 3. Describe fcc, bcc and hcp crystals of simple ionic compounds. 4. Discuss the characteristics of solids. Give the classification of solids into ionic, covalent, molecular and metallic solids. 5. Explain the crystal defects and their origin in the crystal. 26 +2 CHEMISTRY (VOL. - II) E. Multiple cho