chemistry xi - part-i

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Chemistry

Part I

Textbook for Class XI


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FOREWORD

The National Curriculum Framework (NCF), 2005 recommends that childrens life atschool must be linked to their life outside the school. This principle marks a departurefrom the legacy of bookish learning which continues to shape our system and causes agap between the school, home and community. The syllabi and textbooks developed onthe basis of NCF signify an attempt to implement this basic idea. They also attempt todiscourage rote learning and the maintenance of sharp boundaries between differentsubject areas. We hope these measures will take us significantly further in the direction ofa child-centred system of education outlined in the National Policy on Education (1986).

The success of this effort depends on the steps that school principals and teachers

will take to encourage children to reflect on their own learning and to pursueimaginative activities and questions. We must recognise that, given space, time andfreedom, children generate new knowledge by engaging with the information passedon to them by adults. Treating the prescribed textbook as the sole basis of examinationis one of the key reasons why other resources and sites of learning are ignored.Inculcating creativity and initiative is possible if we perceive and treat children asparticipants in learning, not as receivers of a fixed body of knowledge.

These aims imply considerable change in school routines and mode of functioning.Flexibility in the daily time-table is as necessary as rigour in implementing the annualcalender so that the required number of teaching days are actually devoted to teaching.The methods used for teaching and evaluation will also determine how effective thistextbook proves for making childrens life at school a happy experience, rather than a

source of stress or boredom. Syllabus designers have tried to address the problem ofcurricular burden by restructuring and reorienting knowledge at different stageswith greater consideration for child psychology and the time available for teaching.The textbook attempts to enhance this endeavour by giving higher priority and spaceto opportunities for contemplation and wondering, discussion in small groups, andactivities requiring hands-on experience.

The National Council of Educational Research and Training (NCERT) appreciatesthe hard work done by the textbook development committee responsible for this book.We wish to thank the Chairperson of the advisory group in science and mathematics,Professor J.V. Narlikar and the Chief Advisor for this book, Professor B. L. Khandelwalfor guiding the work of this committee. Several teachers contributed to the developmentof this textbook; we are grateful to their principals for making this possible. We areindebted to the institutions and organisations which have generously permitted us todraw upon their resources, material and personnel. As an organisation committed tosystemic reform and continuous improvement in the quality of its products, NCERTwelcomes comments and suggestions which will enable us to undertake furtherrevision and refinement.

Director

New Delhi National Council of Educational20 December 2005 Research and Training


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TEXTBOOK DEVELOPMENT COMMITTEE

CHAIRPERSON, ADVISORYGROUPFOR TEXTBOOKSIN SCIENCEAND MATHEMATICS

J.V. Narlikar, Emeritus Professor, Chairman, Advisory Committee, InterUniversity Centre for Astronomy and Astrophysics (IUCCA), Ganeshbhind,Pune University, Pune

CHIEFADVISOR

B.L. Khandelwal, Professor (Retd.), Emeritus Scientist, CSIR; Emeritus Fellow, AICTEand formerlyChairman, Department of Chemistry, Indian Institute of Technology,New Delhi

MEMBERS

A. S. Brar, Professor, Indian Institute of Technology, Delhi

Anjni Koul, Lecturer, DESM, NCERT, New Delhi

H.O. Gupta, Professor, DESM, NCERT, New Delhi

I.P. Aggarwal, Professor, Regional Institute of Education, NCERT, Bhopal

Jaishree Sharma, Professor, DESM, NCERT, New Delhi

M. Chandra, Professor, DESM, NCERT, New Delhi

Poonam Sawhney, PGT(Chemistry), Kendriya Vidyalaya, Vikas Puri, New DelhiR.K. Parashar, Lecturer, DESM NCERT, New Delhi

S.K. Dogra, Professor, Dr. B.R. Ambedkar Centre for Biomedical Research DelhiUniversity, Delhi

S.K. Gupta, Reader, School of Studies in Chemistry, Jiwaji University, Gwalior

Sadhna Bhargava, PGT(Chemistry), Sardar Patel Vidyalaya, Lodhi Estate, New Delhi

Shubha Keshwan, Headmistress, Demonstration School, Regional Institute of Education,NCERT, Mysore

Sukhvir Singh, Reader, DESM, NCERT, New Delhi

Sunita Malhotra, Professor, School of Sciences, IGNOU, Maidan Garhi, New DelhiV.K. Verma, Professor(Retd.) Institute of Technology, Banaras Hindu University, Varanasi

V.P. Gupta, Reader, Regional Institute of Education, NCERT, Bhopal

MEMBER-COORDINATOR

Alka Mehrotra, Reader, DESM, NCERT, New Delhi


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ACKNOWLEDGEMENTS

The National Council of Educational Research and Training acknowledges the valuablecontributions of the individuals and organisations involved in the development ofChemistry textbook for Class XI. It also acknowledges that some useful material fromthe reprint editions (2005) of Chemistry textbooks has been utilised in the developmentof the present textbook. The following academics contributed very effectively for editing,reviewing, refining and finalisation of the manuscript of this book: G.T. Bhandage,Professor, RIE, Mysore; N. Ram, Professor, IIT, New Delhi; R. S. Sindhu, Reader, RIE(NCERT), Bhopal; Sanjeev Kumar, Reader, Desh Bandhu College, Kalkaji, New Delhi;Shampa Bhattacharya, Reader, Hans Raj College, Delhi; Vijay Sarda, Reader,Zakir Husain College, New Delhi. K.K. Arora, Reader, Zakir Husain College, New Delhi;

Shashi Saxena, Reader, Hans Raj College, Delhi; Anuradha Sen, Apeejay School,Sheikh Sarai, New Delhi; C.Shrinivas, PGT, Kendriya Vidyalaya, Pushp Vihar,New Delhi; D.L. Bharti, PGT, Ramjas School, Sector IV, R.K. Puram, New Delhi;Ila Sharma, PGT, Delhi Public School, Dwarka, Sector-B, New Delhi; Raj LakshmiKarthikeyan, Head(Science), Mothers International School, Sri Aurobindo Marg, NewDelhi; Sushma Kiran Setia, Principal, Sarvodaya Kanya Vidyalaya, Hari Nagar (CT),New Delhi; Nidhi Chaudray, PGT, CRPF Public School, Rohini, Delhi; and Veena Suri,PGT, Bluebells School, Kailash, New Delhi. We are thankful to them.

Special thanks are due to M. Chandra, Professor and Head, DESM, NCERT forher support.

The Council also gratefully acknowledges the contribution of Surendra Kumar,Narender Verma, Ramesh KumarDTP Operator; Subhash Saluja, Ramendra KumarSharma andAbhimanyu Mohanty, Proof Readers; Bhavna Saxena, Copy EditorandDeepak Kapoor, Incharge, Computer Station,in shaping this book. The contributionsof the Publication Department in bringing out this book are also duly acknowledged.


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CONTENTS

Foreword iii

Unit 1 Some Basic Concepts of Chemistry 1

1.1 Importance of Chemistry 1

1.2 Nature of Matter 2

1.3 Properties of Matter and their Measurement 4

1.4 Uncertainty in Measurement 8

1.5 Laws of Chemical Combinations 111.6 Daltons Atomic Theory 13

1.7 Atomic and Molecular Masses 13

1.8 Mole concept and Molar Masses 15

1.9 Percentage Composition 15

1.10 Stoichiometry and Stoichiometric Calculations 17

Unit 2 Structure of Atom 26

2.1 Sub-atomic Particles 27

2.2 Atomic Models 29

2.3 Developments Leading to the Bohrs Model of Atom 34

2.4 Bohrs Model for Hydrogen Atom 42

2.5 Towards Quantum Mechanical Model of the Atom 46

2.6 Quantum Mechanical Model of Atom 49

Unit 3 Classification of Elements and Periodicity in Properties 70

3.1 Why do we need to Classify Elements ? 70

3.2 Genesis of Periodic Classification 71

3.3 Modern Periodic Law and the present form of the Periodic Table 75

3.4 Nomenclature of Elements with Atomic Number > 100 75

3.5 Electronic Configurations of Elements and the Periodic Table 78

3.6 Electronic Configurations and Types of Elements: 79

s, p, d, f-Blocks

3.7 Periodic Trends in Properties of Elements 82


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Unit 4 Chemical Bonding and Molecular Structure 96

4.1 Kssel-Lewis Approach to Chemical Bonding 97

4.2 Ionic or Electrovalent Bond 102

4.3 Bond Parameters 103

4.4 The Valence Shell Electron Pair Repulsion (VSEPR) Theory 108

4.5 Valence Bond Theory 113

4.6 Hybridisation 116

4.7 Molecular Orbital Theory 121

4.8 Bonding in Some Homonuclear Diatomic Molecules 125

4.9 Hydrogen Bonding 127

Unit 5 States of Matter 132

5.1 Intermolecular Forces 133

5.2 Thermal Energy 135

5.3 Intermolecular Forces vs Thermal Interactions 135

5.4 The Gaseous State 135

5.5 The Gas Laws 136

5.6 Ideal Gas Equation 141

5.7 Kinetic Molecular Theory of Gases 143

5.8 Behaviour of real gases: Deviation from Ideal Gas Behaviour 144

5.9 Liquifaction of Gases 147

5.10 Liquid State 149

Unit 6 Thermodynamics 154

6.1 Thermodynamic State 155

6.2 Applications 158

6.3 Measurement ofUand H: Calorimetry 163

6.4 Enthalpy Change, rHof a Reaction 164

6.5 Enthalpies for Different Types of Reactions 170

6.6 Spontaneity 174

6.7 Gibbs Energy Change and Equilibrium 179

Unit 7 Equilibrium 185

7.1 Equilibrium in Physical Processes 186

7.2 Equilibrium in Chemical Processes Dynamic Equilibrium 189

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7.3 Law of Chemical Equilibrium and Equilibrium Constant 191

7.4 Homogeneous Equilibria 194

7.5 Heterogeneous equilibria 197

7.6 Applications of Equilibrium Constants 198

7.7 Relationship between Equilibrium ConstantK, 201

Reaction QuotientQand Gibbs EnergyG

7.8 Factors Affecting Equilibria 201

7.9 Ionic Equilibrium in Solution 205

7.10 Acids, Bases and Salts 206

7.11 Ionization of Acids and Bases 209

7.12 Buffer Solutions 219

7.13 Solubility Equilibria of Sparingly Soluble Salts 220

Appendices 231

Answers 245

Index 251

Supplementary Material I IV

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chemistry xi - part-i

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