Chemistry

Part I

Textbook for Class XI

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2 CHEMISTRY

First Edition

March 2006 Phalguna 1927

ReprintedOctober 2006 Kartika 1928

November 2007 Kartika 1929

January 2009 Magha 1930

December 2009 Pausa 1931

November 2010 Kartika 1932January 2012 Pausha 1933

November 2012 Kartika 1934

November 2013 Kartika 1935

PD 400T MJ

© National Council of Educational

Research and Training, 2006

`̀̀̀̀ 125.00

Printed on 80 GSM paper with NCERT

watermark

Published at the Publication Division

by the Secretary, National Council ofEducational Research and Training, Sri

Aurobindo Marg, New Delhi 110 016 and printedat Supreme Offset Press, K-5, Malviya Nagar,

New Delhi 110 017

ISBN 81-7450-494-X (Part I)

ALL RIGHTS RESERVED

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of binding or cover other than that in which it is published.

q The correct price of this publication is the price printed on this page, Any revisedprice indicated by a rubber stamp or by a sticker or by any other means is incorrectand should be unacceptable.

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Manager

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Cover

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3ANSWERS

FOREWORD

The National Curriculum Framework (NCF), 2005 recommends that children’s life at

school 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 a

gap between the school, home and community. The syllabi and textbooks developed on

the basis of NCF signify an attempt to implement this basic idea. They also attempt todiscourage rote learning and the maintenance of sharp boundaries between different

subject 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 and

freedom, children generate new knowledge by engaging with the information passedon to them by adults. Treating the prescribed textbook as the sole basis of examination

is 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 annual

calender 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 children’s 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 stages

with 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, and

activities requiring hands-on experience.

The National Council of Educational Research and Training (NCERT) appreciates

the 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. Khandelwal

for 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 are

indebted to the institutions and organisations which have generously permitted us to

draw upon their resources, material and personnel. As an organisation committed tosystemic reform and continuous improvement in the quality of its products, NCERT

welcomes 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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4 CHEMISTRY

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5ANSWERS

TEXTBOOK DEVELOPMENT COMMITTEE

CHAIRPERSON, ADVISORY GROUP FOR TEXTBOOKS IN SCIENCE AND MATHEMATICS

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

Pune University, Pune

CHIEF ADVISOR

B.L. Khandelwal, Professor (Retd.), Emeritus Scientist, CSIR; Emeritus Fellow, AICTEand formerly Chairman, 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 Delhi

R.K. Parashar, Lecturer, DESM NCERT, New Delhi

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

University, 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 Delhi

V.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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6 CHEMISTRY

ACKNOWLEDGEMENTS

The National Council of Educational Research and Training acknowledges the valuable

contributions of the individuals and organisations involved in the development ofChemistry textbook for Class XI. It also acknowledges that some useful material from

the reprint editions (2005) of Chemistry textbooks has been utilised in the development

of 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(NCER T), 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 Lakshmi

Karthikeyan, 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 for

her support.

The Council also gratefully acknowledges the contribution of Surendra Kumar,

Narender Verma, Ramesh Kumar DTP Operator; Subhash Saluja, Ramendra KumarSharma and Abhimanyu Mohanty, Proof Readers; Bhavna Saxena, Copy Editor and

Deepak Kapoor, Incharge, Computer Station, in shaping this book. The contributions

of the Publication Department in bringing out this book are also duly acknowledged.© NCERT

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7ANSWERS

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 11

1.6 Dalton’s 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 Bohr’s Model of Atom 34

2.4 Bohr’s 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 Kössel-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 of ∆U and ∆H: Calorimetry 163

6.4 Enthalpy Change, ∆rH of 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 Constant K, 201

Reaction Quotient Q and Gibbs Energy G

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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