11th Chemistry Vol-1 English Medium Textbook PDF

GOVERNMENT OF TAMIL NADU HIGHER SECONDARY FIRST YEAR CHEMISTRY VOLUME - I A publication under Free Textbook Programme of Government...

GOVERNMENT OF TAMIL NADU HIGHER SECONDARY FIRST YEAR CHEMISTRY VOLUME - I A publication under Free Textbook Programme of Government of Tamil Nadu Department of School Education Untouchability is Inhuman and a Crime 11th Chemistry Introduction Pages Vol-1 EM.indd 1 09-01-2023 13:56:01  Government of Tamil Nadu First Edition - 2018 Revised Edition - 2019, 2020, 2021, 2022, 2023 Reprint - 2 024 (Published under New Syllabus) NOT FOR SALE Content Creation The wise possess all State Council of Educational Research and Training © SCERT 2018 Printing & Publishing Tamil NaduTextbook and Educational Services Corporation www.textbooksonline.tn.nic.in II 11th Chemistry Introduction Pages Vol-1 EM.indd 2 13/12/2023 13:32:39  Key features Awareness about higher education avenues in Scope of Chemistry the field of Chemistry Describe the specific competency / Learning objectives performance capability acquired by the learner Additional information provided to relate the Do you know content to day-to-day life / development in the field Model problems worked out for clear-cut Example Problems comprehension by the learners To help the students to assess their own Evaluate yourself conceptual understanding Quick access to concepts, videos, animations Q.R code and tutorials Opens up resources for learning; enables the ICT learners to access, extend transform ideas / informations Summary A glance on the substance of the unit Inter relating the concepts for enabling learners Concept map to visualize the essence of the unit To assess the level of understanding through Evaluation multiple choice question,numerical problems etc. Books for Reference List of relevant books for further reading To help the learners confirm the accuracy of Key answers the answers arrived and remedy the gaps in learning Important terms are enlisted with equivalent Glossary Tamil words Comprises fundamental constants and Data Appendix tables III 11th Chemistry Introduction Pages Vol-1 EM.indd 3 09-01-2023 13:56:02 11th Introduction Introduction Chemistry Pages.indd Pages.indd The courses offered, top colleges and competitive exams conducted for higher education after 4 4 Introduction 12th in Chemistry field were summarized below. Pages Vol-1 EM.indd 4 Courses Institution Selection Mode Careers in Chemistry Bachelor Degree th B.Sc. (Chemistry) Arts and Science Colleges in India Counseling based on 12 Marks in Teacher for Secondary Schools B.Sc. (Analytical Methods in Science Subjects Lab Chemist Chemistry) Food Processing Firms B.Sc. (Applied Chemistry) Paint Manufacturing Companies B.Sc. (Industrial Chemistry) Plastics Industries and Textile Industries B.Sc. (Polymer Chemistry) Agrochemical Industry B.Sc. (Bio Chemistry) Petrochemical Industry Water Quality and Cosmetic Chemists Can write any type of competitive examinations such as TNPSC, Bank exams, Civil service, IV IV RRB etc. # B.E.(Chemical Engineering) Indian Institute of Technologies JEE (Main & Advanced) # Birla Institute of Technology and Science BITSAT All Govt. and Private Engineering colleges in Architectural engineering works Tamilnadu Resin and artificial synthetic fibers Petroleum and coal products manufacturing B.Tech.(Rubber plastics technology) Madras Institute of Technology Space Fuel Processor B.Tech.(Petroleum Refining Anna University, Alagappa College of TNEA Counseling based on cut off Biotechnology and pharmaceutical companies and Petrochemicals, Ceramic Technology, CSIR-Central Leather scored in 12th std Climate Change Reversal Engineer Technology(S.S), Textile Technology, Research Institute and other affiliated Food Manufacturing unites, Electronics and Leather Technology) colleges Energy manufacturers B.E. / B.Tech. (Plastics Engineering / Central Institute of Plastics Engineering & Technology) Technology Diploma Advanced Diploma in Technical and Maharashtra State Board of Technical Counseling based on percentage Chemical, pharmaceutical, food and paint Analytical Chemistry (ADTAC) Education (MSBTE) - Government of scored in degree industries as Analysts, Chemists and Q.C. Maharashtra. (Eligibility: Any Degree) Chemists # Plastics Processing & Testing Central Institute of Plastics Engineering & JEE Plastics Industries Technology Masters Degree 31-03-2018 09-01-2023 11-01-2021 13:34:17 13:56:03 15:20:29  Courses Institution Selection Mode Careers in Chemistry Bachelor Degree # Pondicherry University Pondicherry University Entrance exam Indian Institute of Technology (IIT Roorkee) # Indian Institute of Technology (IIT Joint Admission Test for M.Sc. Khagarpur) (JAM) 11th Chemistry Introduction Pages Vol-1 EM.indd 5 Indian Institute of Technology (IIT Bombay) Analytical Chemist Central University of Tamil Nadu : School of # CUCET entrance Higher Secondary Teacher Basic and Applied Science, Thiruvarur Production Chemist M.Sc. (Integrated Chemistry) NISER School of Chemical Sciences, # NEST entrance Research & Development Manager Cuttack Biomedical Chemist # Industrial Research Scientist Birla Institute of Technology and Science BITSAT entrance Materials Technologist Annamalai University #Annamalai University Entrance exam Quality Controller Safety Health and Environment Specialist Arts and Science Colleges in India Based on percentage scored in Pharmaceutical Companies degree and Separate Entrance Environmental Law exams will be conducted by the V Space Exploration Agencies concern institute Forensic Science Department Government Universities like Ceramics Industry and Paper Industry University of Madras, Alagappa University, Military Systems Department M.Sc.-General Chemistry, Anna University, Patent Attorney Analytical Chemistry, Inorganic Annamalai University, Nuclear engineer Chemistry Organic Chemistry, Physical Bharathiar University, Separate Entrance exams will be Chemistry, Bharathidasan University, conducted by the concern institute Polymer Chemistry Madurai Kamaraj University and IISc, Environmental Science Bangalore, NanoScience and Nanotechnology University of Delhi, etc. Arts and Sciences colleges in India M.Sc. Applied Chemistry Anna University Industry related jobs Chemistry (Hons) Applied Andhra University Quality Control Chemist Chemistry(Hons) Birla Institute of Technology Cochin Production Chemist Separate Entrance exams will be Industrial Chemistry University of Science and technology Petrochemical industry conducted by the concern institute Medicinal Chemistry PSG College, Coimbatore Food processing Pharmaceutical Chemistry Sri Venkateshwara University, Tirupati. Paint industry Drug Chemistry 09-01-2023 13:56:03  Courses Institution Selection Mode Careers in Chemistry Bachelor Degree M.Tech. -Polymer Science Anna University and Alagappa College of # Tamil Nadu Common Entrance Industrial Safety and Hazards Management And Technology Technology Test (TANCET) jobs in various industry Industrial Safety And Hazards Management 11th Chemistry Introduction Pages Vol-1 EM.indd 6 M.Phil. M.Phil.-Chemistry Universities in India Entrance/direct interview Teaching related jobs Analytical Chemistry Arts and Science Colleges in India depending upon the College/ All industries related jobs Applied Chemistry University Technicians in imaging labs Industrial Chemistry Patent Law Crystal Science Research Ph.D. (Chemistry) Indian Institute of Science, Indian Institute of Separate Entrance exams will be Area: Technology, Kharagpur conducted by the concern institute Organic Synthesis, Inorganic University of Delhi, Delhi complexes, Computational Chemistry, Indian Institute of Technology, Bombay Nanotechnology Professor for Govt. colleges and Universities Tata Institute of Fundamental Research, Electrochemistry, Material Science Mumbai Chemical scientists VI & Polymer Composites, Bio- Anna University, Chennai Scientist posts in many central government industry sensors, Molecular modelling, Indian Institute of Technology, Madras chemoinformatics, Green Chemistry, Jawaharlal Nehru Centre for Advanced Post Doctoral Fellow Catalysts for Green Oxidation Quality control in Toxicology Chemistry University of Madras, Formulation Chemistry etc. Bharathiar University, Chemical Information Management Specialist Jawaharlal Nehru University, National Institute of Technology, Annamalai University, etc. 09-01-2023 13:56:03  Entrance Exams and Pattern Indian Institutes of Information 30 Technology (IIITs) 30 Indian Institute of Engineering Science 30 JEE-Main OMR based Notification: 1st week of Dec and Technology (IIEST) Physics 90 Paper I -3 hrs and Online Exam Date: April 11th Chemistry Introduction Pages Vol-1 EM.indd 7 National Institutes of Technology Chemistry Mathematics Paper II-3 hrs based (choice of Negative marking: 4/-1 (NITs) Total Questions www.jeemain.nic.in candidate) Total Marks:360 Indian Institute of Technology (IITs) Government Funded Technical Institutes (GFTIs) Indian Institutes of Information 18 Technology (IIITs) 18 JEE-Advanced Indian Institute of Engineering Science 18 Paper I -3 hrs Notification: last week of April and Technology (IIEST) Physics 54 Paper II-3 hrs Exam Date: May second week National Institutes of Technology Online Chemistry Mathematics Should qualify JEE main Negative marking: 4/-1 (NITs) Total Questions (paper-I) Total Marks: 306 (Variable each year) Indian Institute of Technology (IITs) www.jeeadv.ac.in Government Funded Technical VII Institutes (GFTIs) Physics 40 BITSAT Notification: 2nd week of Dec Chemistry 40 http://www.bitsadmission. Birla Institute of Technology and Exam Date: 2nd week of May Mathematics 45 Online com Science Negative marking: 3/-1 15 Time: 3 hrs Total Marks: 450 Logical Reasoning 10 Total Questions 150 English 25 nd General Awareness 25 Notification: 2 week of Feb CUCET Mathematical Aptitude 25 Exam Date: April https://cucetexam.in All Central Universities Online Negative marking: 1/0.25 Time: 2 hrs Analytical Skill 25 Total Marks:175 Science 75 Total Questions 175 Notification: September 60 JAM Exam Date: February 60 Chemistry http://jam.iitb.ac.in/ All IITs Online Negative marking: 1/0.33 Total Questions Time: 3 hrs 2/0.66 Total Marks:100 09-01-2023 13:56:03  60 Sessions: June General Science, From out : March Quantitative Reasoning CSIR-UGC Net Ph.D. admission in all Universities and Exam Date: June & Analysis and Research http://csirhrdg.res.in OMR Colleges Session: December Aptitude Time: 3 hrs From out : September Chemistry 15 Exam Date: December Total Questions 75 11th Chemistry Introduction Pages Vol-1 EM.indd 8 From out : September Exam Date: February General Aptitude 10 GATE http://gate.iitg.ac.in/ Ph.D. admission in all IITs OMR Negative marking: 1/0.33 Chemistry 55 Time: 3 hrs 2/0.66 Total Questions 65 Total Marks:100 Engineering Mathematics 20 From out : January TANCET Basic Engineering and Anna University Entrance exam for Pen and Paper Exam Date: March 20 https://www.annauniv.edu Sciences technology courses based exam Negative marking: 1/0.33 Time: 2 hrs Chemistry 60 Total Marks:100 Total Questions 100 Analytical Chemistry 25 From out : 2nd week of Feb University of Madras Inorganic Chemistry 25 Pen and Paper Exam Date: April http://www.unom.ac.in M.Sc. Entrance exam Organic Chemistry Physical 25 based exam Negative marking: Nil VIII Time: 3 hrs Chemistry 25 Total Marks:100 Total Questions 100 From out : April Anna University Exam Date : May Chemistry 100 https://www.annauniv.edu M.Sc. Entrance exam Online Negative marking : 1/0.25 Total Questions 100 Time: 1 hr Total Marks : 100 Annamalai University M.Sc. Admission Based on percentage scored in degree and Personal Interview. http://www. annamalaiuniversity.ac.in B.Sc. Admission Counseling based on 12th Marks in Science Subjects Bharathiar University From out : May 60 Pen and Paper Chemistry www. b-u.ac.in M.Sc. Entrance exam Exam Date : Roughly July 60 based exam Total Questions Time: 1.30 hrs Total Marks : 60 Bharathidasan University Pen and Paper From out : last week of May M.Sc. Entrance exam http://www.bdu.ac.in/ based exam Exam Date : second week of June Madurai Kamaraj From out : March University M.Sc. Entrance exam Online Exam Date : May/June mkuniversity.ac.in (Note: All these dates are tentative and they are subjected to change every year) 09-01-2023 13:56:03  CONTENTS CHEMISTRY Unit Topic Page.No. Month No. Basic Concepts of Chemistry and Chemical 1 01 June Calculations 2 Quantum Mechanical Model of Atom 38 July 3 Periodic Classification Of Elements 68 August 4 Hydrogen 100 September 5 Alkali and Alkaline Earth Metals 125 October 6 Gaseous State 158 June 7 Thermodynamics 186 July Appendix 229 E-book Assessment IX 11th Chemistry Introduction Pages Vol-1 EM.indd 9 09-01-2023 13:56:04  HIGHER SECONDARY FIRST YEAR CHEMISTRY X 11th Chemistry Introduction Pages Vol-1 EM.indd 10 09-01-2023 13:56:04  Unit 1 Basic Concepts of Chemistry and Chemical Calculations Learning Objectives After studying this unit, students will be able to explain the importance of chemistry in different spheres of life. classify different substances into elements, We think there is colour, we compounds and mixtures. think there is sweet, we think define atomic mass and molecular mass. there is bitter, but in reality there are atoms and a void. define the amount of substance using SI unit – Democritus 'mole'. describe Avogadro number. explain the relationship among mass, moles and Natural Fibre (Cotton) number of atoms (or) molecules and perform calculations relating to the conversions. define equivalent mass and calculate equivalent mass of acid, base and oxidising/reducing agents. Synthetic Fibre deduce empirical and molecular formula of a (Nylon) compound from experimental data. solve numerical problems based on stoichiometric calculations. (Malathion) identify the limiting reagent and calculate the Pesticide amount of reactants and products in a reaction. define the terms oxidation, reduction, oxidant and reductant. Pharmaceutical predict the oxidation states of elements in various (Tablets) compounds. explain the process involved in a redox reaction and describe the electron transfer process. classify redox reactions into different types. Refinery (Oil) formulate a balanced redox reaction from two half-reactions. 1 11th Std Chemistry 001-037.indd 1 23-12-2021 15:03:12  1.1 Chemistry - the Centre of Life 'Unna unavu, udukka udai, irukka infection, and people with HIV infection idam' - in Tamil classical language means have longer and better life. food to eat, cloth to wear and place to The understanding of chemical live. These are the three basic needs of principles enabled us to replace the non human life. Chemistry plays a major role eco friendly compounds such as CFCs in in providing these needs and also helps us refrigerators with appropriate equivalents to improve the quality of life. Chemistry and increasing number of green processes. has produced many compounds such as There are many researchers working in fertilizers, insecticides etc. that could different fields of chemistry to develop new enhance the agricultural production. We drugs, environment friendly materials, build better and stronger buildings that synthetic polymers etc. for the betterment sustain different weather conditions with of the society. modern cements, concrete mixtures and better quality steel. We also have better As chemistry plays an important quality fabrics. role in our day-to-day life, it becomes essential to understand the basic principles Chemistry is everywhere in the of chemistry in order to address the world around us. Even our body is mounting challenges in our developing made up of chemicals. Continuous bio- country. chemical reactions occurring in our body are responsible for human activities. 1.2 Classification of Matter: Chemistry touches almost every aspect of our lives, culture and environment. The Look around your classroom. What world in which we are living is constantly do you see? You might see your bench, changing, and the science of chemistry table, blackboard, window etc. What are continues to expand and evolve to meet these things made of ? They are all made of the challenges of our modern world. matter. Matter is defined as anything that Chemical industries manufacture a broad has mass and occupies space. All matter range of new and useful materials that are is composed of atoms. This knowledge of used in every day life. matter is useful to explain the experiences that we have with our surroundings. In Examples : polymers, dyes, alloys, order to understand the properties of life saving drugs etc. matter better, we need to classify them. When HIV/AIDS epidemic began There are different ways to classify matter. in early 1980s, patients rarely lived longer The two most commonly used methods than a few years. But now many effective are classification by their physical state medicines are available to fight the and by chemical composition as described in the chart. 2 11th Std Chemistry 001-037.indd 2 23-12-2021 15:03:12  Matter or heterogeneous mixtures based on their physical appearance. Physical classification Pure substances are composed of simple atoms or molecules. They Solid Liquid Gas are further classified as elements and compounds. Ice Water Water Vapour Element : Chemical Classification An element consists of only one type of atom. We know that an atom is the Mixtures smallest electrically neutral particle, being made up of fundamental particles, namely homogeneous heterogeneous electrons, protons and neutrons. Green tea Oil and Water Element can exist as monatomic or polyatomic units. Pure Substances Example : Monatomic unit - Gold (Au), Copper (Cu); Polyatomic unit - Elements Compounds Hydrogen (H2), Phosphorous (P4) and Sulphur (S8) Copper Copper Sulphate Compound: Compounds are made up of Fig. 1.1 Classification of Matter molecules which contain two or more 1.2.1 Physical Classification of Matter : atoms of different elements. Matter can be classified as solids, Example : Carbon dioxide liquids and gases based on their physical (CO2), Glucose (C6H12O6), Hydrogen state. The physical state of matter can be Sulphide (H2S), Sodium Chloride (NaCl) converted into one another by modifying the temperature and pressure suitably. Properties of compounds are different from those of their constituent 1.2.2 Chemical Classification : elements. For example, sodium is a shiny metal, and chlorine is an irritating gas. Matter can be classified into But the compound formed from these mixtures and pure substances based on two elements, sodium chloride, shows chemical compositions. Mixtures consist different characteristics as it is a crystalline of more than one chemical entity present solid, vital for biological functions. without any chemical interactions. They can be further classified as homogeneous 3 11th Std Chemistry 001-037.indd 3 23-12-2021 15:03:15  Relative atomic mass (Ar) Evaluate Yourself 1.1? Average mass of the atom 1) By applying the knowledge of = Unified atomic mass chemical classification, classify each of the following into elements, For example, compounds or mixtures. Relative atomic mass of hydrogen (Ar)H (i) Sugar Average mass of H-atom (in kg) (ii) Sea water = (iii) Distilled water 1.6605 × 10–27 kg (iv) Carbon dioxide 1.6736 × 10–27 kg (v) Copper wire = (vi) Table salt 1.6605 × 10–27 kg (vii) Silver plate = 1.0078 ≈ 1.008 u. (viii) Naphthalene balls Since most of the elements consist 1.3 Atomic and Molecular Masses of isotopes that differ in mass, we use average atomic mass. Average atomic mass 1.3.1 Atomic Masses is defined as the average of the atomic masses of all atoms in their naturally How much does an individual occurring isotopes. For example, chlorine atom weigh? As atoms are too small consists of two naturally occurring with diameter of 10–10 m and weigh isotopes 17Cl35 and 17Cl37 in the ratio 77 approximately 10–27 kg, it is not possible : 23, the average relative atomic mass of to measure their mass directly. Hence it is chlorine is proposed to have relative scale based on a (35 × 77) + (37 × 23) = standard atom. 100 The C-12 atom is considered as = 35.46 u standard by the IUPAC (International Union of Pure and Applied Chemistry), 1.3.2 Molecular Mass and its mass is fixed as 12 amu (or) u. Similar to relative atomic mass, The amu (or) unified atomic mass unit relative molecular mass is defined as the is defined as one twelfth of the mass of a ratio of the mass of a molecule to the Carbon-12 atom in its ground state. unified atomic mass unit. The relative molecular mass of any compound can be i.e. 1 amu (or) 1u ≈ 1.6605 × 10–27 kg. calculated by adding the relative atomic masses of its constituent atoms. In this scale, the relative atomic For example, mass is defined as the ratio of the average atomic mass to the unified atomic i) Relative molecular mass of hydrogen mass unit. molecule (H2) 4 11th Std Chemistry 001-037.indd 4 23-12-2021 15:03:15  = 2 × (relative atomic mass of hydrogen atom) roses means 12 roses and one quire paper means 24 single sheets. We can extend = 2 × 1.008 u this analogy to understand the concept of mole that is used for quantifying atoms = 2.016 u. and molecules in chemistry. Mole is the SI unit to represent a specific amount of a ii) Relative molecular mass of glucose (C6H12O6) substance. = (6 × 12) + ( 12 ×1.008) + (6 ×16) To understand the mole concept, let us calculate the total number of atoms = 72+12.096+96 present in 12 g of carbon -12 isotope or molecules in 158.03 g of potassium = 180.096 u permanganate, 294.18 g of potassium dichromate and 180 g of glucose. Table 1.1 Relative atomic masses of some elements 12 Numbers = 1 Dozen Relative Relative Element atomic Element atomic mass mass H 1.008 Cl 35.45 C 12 K 39.10 N 14 Ca 40.08 12 Roses 12 Balls O 16 Cr 51.99 Na 23 Mn 54.94 Mg 24.3 Fe 55.85 S 32.07 Cu 63.55 Evaluate Yourself ? 12 Apples 2) Calculate the relative molecular mass of the following. 1 Mole ≡ 6.023 × 1023 entities (i) Ethanol(C2H5OH) (ii) Potassium permanganate (KMnO4) (iii) Potassium dichromate (K2Cr2O7) (iv) Sucrose (C12H22O11) 1.4 Mole Concept 158.03g of KMnO4 294.18g of K2Cr2O7 Often we use special names to express the quantity of individual items Fig. 1.2 Mole Concept for our convenience. For example, a dozen 5 11th Std Chemistry 001-037.indd 5 23-12-2021 15:03:17  Table 1.2 Calculation of number of entities in one mole of substance. Mass of single atom Mass of the or molecule (gram) No. of atoms or molecules = Name of substance S. No. = Atomic mass Mass of substance ÷ Mass of substance taken or Molar mass / single atom or molecule (gram) Avovadro Number (1) (2) (3) (2)÷(3) Elemental 12 1. 12 1.9926 x 10-23 = 6.022 × 1023 Carbon (C-12) 1.9926 × 10-23 Glucose 180 2. 180 29.89 x 10-23 = 6.022 × 1023 (C6H12O6) 29.89 × 10-23 Potassium 294.18 3. dichromate 294.18 48.851 x 10-23 = 6.022 × 1023 (K2Cr2O7) 48.851 × 10-23 Potassium 158.03 4. permanganate 158.03 26.242 × 10-23 = 6.022 × 1023 (KMnO4) 26.242 × 10-23 From the calculations we come to know that 12 g of carbon-12 contains 6.022x1023 carbon atoms and same numbers of molecules are present in 158.03 g of potassium permanganate and 294.18 g of potassium dichromate. Similar to the way we use the term ‘dozen’ to represent 12 entities, we can use the term ‘mole’ to represent 6.022 x 1023 entities (atoms or molecules or ions) One mole is the amount of substance of a system, which contains as many elementary particles as there are atoms in 12 g of carbon-12 isotope. The elementary particles can be molecules, atoms, ions, electrons or any other specified particles. Gastric acid and antacids: Antacids used to treat acidity contain mostly magnesium hydroxide or Antacids are commonly aluminium hydroxide that neutralises the used medicines for treating excess acid. The chemical reactions are as heartburn and acidity. Do follows. you know the chemistry behind it? 3 HCl + Al(OH)3→ AlCl3 + 3 H2O Gastric acid is a digestive fluid formed in the stomach and it 2 HCl + Mg(OH)2→MgCl2 + 2 H2O contains hydrochloric acid. The typical From the above reactions we know concentration of the acid in gastric acid is that 1 mole of aluminium hydroxide 0.082 M. When the concentration exceeds neutralises 3 moles of HCl while 1 mole of 0.1 M it causes the heartburn and acidity. magnesium hydroxide neutralises 2 moles of HCl. 6 11th Std Chemistry 001-037.indd 6 23-12-2021 15:03:17  Let us calculate the amount of acid One tablet of above composition will neutralised by an antacid that contains neutralise 0.0182 mole of HCl for a person 250 mg of aluminium hydroxide and with gastric acid 250 mg of magnesium hydroxide. content of 0.1 mole. One tablet Acidity & Compound moles OH- compound Molecular (g mol-1) Heart burn of active can be used Mass in Active No. of No. of moles mass (mg) to neutralize the excess acid Al(OH)3 250 78 0.0032 0.0096 which will bring the concentration back Mg(OH)2 250 58 0.0043 0.0086 to normal level. (0.1 – 0.018 = 0.082 M) Total no. of moles of OH- ion from one tablet 0.0182 1.4.1 Avogadro Number: The total number of entities present Lorenzo Romano in one mole of any substance is equal Amedeo Carlo to 6.022 x 1023. This number is called Avogadro (1776-1856) Avogadro number which is named after the Italian physicist Amedeo Avogadro He is known for the Avogadro's who proposed that equal volume of hypothesis. In honour of his contributions, all gases under the same conditions of the number of fundamental particles temperature and pressure contain equal in a mole of substance was named as number of molecules. Avogadro number Avogadro number. Though Avogadro does not have any unit. didn't predict the number of particles in equal volumes of gas, his hypothesis did In a chemical reaction, atoms or lead to the eventual determination of the molecules react in a specific ratio. Let us number as 6.022 x 1023 Rudolf Clausius, with his kinetic theory of gases, provided consider the following examples evidence for Avogadro's law. Reaction 1 : C + O2→ CO2 molecules. Because of this reason it is Reaction 2 : CH4 + 2 O2 → CO2 + 2 H2O beneficial to use 'mole' concept rather In the first reaction, one carbon than the actual number of molecules to atom reacts with one oxygen molecule to quantify the reactants and the products. give one carbon dioxide molecule. In the We can explain the first reaction as one second reaction, one molecule of methane mole of carbon reacts with one mole of burns with two molecules of oxygen to oxygen to give one mole of carbon dioxide give one molecule of carbon dioxide and and the second reaction as one mole of two molecules of water. It is clear that the methane burns with two moles of oxygen ratio of reactants is based on the number to give one mole of carbon dioxide and of molecules. Even though the ratio is two moles of water. When only atoms are based on the number of molecules it is involved, scientists also use the term one practically difficult to count the number of gram atom instead of one mole. 7 11th Std Chemistry 001-037.indd 7 23-12-2021 15:03:19  1.4.2 Molar Mass: 1.5 Gram Equivalent Concept: Molar mass is defined as the mass of Similar to mole concept gram one mole of a substance. The molar mass equivalent concept is also widely used of a compound is equal to the sum of the in chemistry especially in analytical relative atomic masses of its constituents chemistry. In the previous section, we expressed in g mol-1. have understood that mole concept is based on molecular mass. Similarly gram Examples: equivalent concept is based on equivalent relative atomic mass of one hydrogen mass. atom = 1.008 u molar mass of hydrogen atom Definition: = 1.008 g mol-1 relative molecular mass of glucose Gram equivalent mass is defined = 180 u as the mass of an element (compound or molar mass of glucose = 180 g mol-1 ion) that combines or displaces 1.008 g hydrogen or 8 g oxygen or 35.5 g chlorine. 1.4.3 Molar Volume: Consider the following reaction: The volume occupied by one mole of any substance in the gaseous state at a Zn+H2SO4 → ZnSO4+H2 given temperature and pressure is called molar volume. In this reaction 1 mole of zinc (i.e. 65.38 g) displaces one mole of hydrogen molecule Volume occupied by one mole of any (2.016 g). Conditions gaseous substances (in litre) Mass of zinc required to displace 1.008 g 273 K and 1 bar 22.71 hydrogen is pressure (STP) 65.38 = × 1.008 273 K and 1 atm pressure 22.4 2.016 65.38 298 K and 1 atm pressure = (Room Temperature & 24.47 2 pressure (SATP) The equivalent mass of zinc = 32.69 Evaluate Yourself ? The gram equivalent mass of zinc 3a) Calculate the number of moles = 32.69 g eq-1 present in 9 g of ethane. Equivalent mass has no unit but 3b) Calculate the number of molecules gram equivalent mass has the unit g eq-1 of oxygen gas that occupies a volume of 224 ml at 273 K and 3 atm pressure. It is not always possible to apply the above mentioned definition which is 8 11th Std Chemistry 001-037.indd 8 23-12-2021 15:03:19  based on three references namely hydrogen, oxygen and chlorine, because we can not conceive of reactions involving only with those three references. Therefore, a more useful expression used to calculate gram equivalent mass is given below. Molar mass (g mol-1) Gram equivalent mass = Equivalence factor (eq mol-1) On the basis of the above expression, let us classify chemical entities and find out the formula for calculating equivalent mass in the table below. 1.5.1 Equivalent Mass of Acids, Bases, Salts, Oxidising Agents and Reducing Agents Chemical Equivalent Formula for calculating entity Example Factor(n) equivalent mass (E) H2SO4 basicity     = 2 eq mol–1 basicity (no. of Molar mass of H2SO4 moles of            = (2 × 1) + (1 × 32) + (4 × 16) ionisable Acids Molar mass of the acid            = 98 g mol-1 H+ ions E= Basicity of the acid 98 present in Gram equivalent mass of H2SO4    = 1 mole of 2 the acid)            = 49 g eq–1 Acidity (no. of KOH acidity      = 1 eq mol–1 moles of Molar mass of KOH         =   (1 × 39)+(1 × 16)+(1 ×1) ionisable Bases Molar mass of the base            = 56 g mol-1 OH– ion E= Acidity of the base Gram equivalent mass of KOH present in 1 mole of 56            = = 56 g eq–1 the base) 1 KMnO4 is an oxidising agent, Oxidising agent (or) reducing agent No. of Molar mass of KMnO4 moles of Molar mass of the electrons oxidising (or)         = (1 × 39) +(1 × 55) + (4 ×16)          gained (or) reducing agent            = 158 g mol-1 lost by one E= No. of moles of In acid medium permanganate is reduced during oxidation mole of the electrons gained or and is given by the following equation, reagent lost by one mole of during MnO4– + 8H+ + 5e– → Mn2+ + 4H2O the oxidising (or) redox reducing agent ∴n = 5 eq mol–1. reaction 158 Gram equivalent mass of KMnO4 = = 31.6 g eq–1. 5 Mole concept requires a balanced chemical reaction to find out the amount of reactants involved in the chemical reaction while gram equivalent concept does not 9 11th Std Chemistry 001-037.indd 9 23-12-2021 15:03:19  require the same. We prefer to use mole 1.6 Empirical Formula concept for non-redox reactions and gram and Molecular Formula equivalent concept for redox reactions. For example, Elemental analysis of a compound gives the mass percentage of atoms If we know the equivalent mass of present in the compound. Using the KMnO4 and anhydrous ferrous sulphate, mass percentage, we can determine the without writing balanced chemical empirical formula of the compound. reaction we can straightaway say that Molecular formula of the compound can 31.6 g of KMnO4 reacts with 152 g of be arrived at from the empirical formula FeSO4 using gram equivalent concept. using the molar mass of the compound. The same can also be explained Empirical formula of a compound on the basis of mole concept. The is the formula written with the simplest balanced chemical equation for the above ratio of the number of different atoms mentioned reaction is present in one molecule of the compound as subscript to the atomic symbol. 10 FeSO4 + 2 KMnO4 + 8 H2SO4 Molecular formula of a compound is the ↓ formula written with the actual number K2SO4 + 2 MnSO4 + 5 Fe2(SO4)3 + 8H2O of different atoms present in one molecule as a subscript to the atomic symbol. i.e. 2 moles (2 × 158 = 316 g) of potassium permanganate reacts with 10 Let us understand the empirical moles (10 × 152 = 1520 g) of anhydrous formula by considering acetic acid as an ferrous sulphate. example. ∴ 31.6 g KMnO4 reacts with The molecular formula of acetic 1520 acid is C2H4O2 × 31.6 = 152 g of FeSO4 316 The ratio of C : H : O is 1 : 2 : 1 and hence the empirical formula is CH2O. Evaluate Yourself ? 4a) 0.456 g of a metal gives 0.606 g of its 1.6.1 Determination of Empirical chloride. Calculate the equivalent Formula from Elemental Analysis Data : mass of the metal. 4b) Calculate the equivalent mass Step 1: Since the composition is of potassium dichromate. The expressed in percentage, we reduction half-reaction in acid can consider the total mass of medium is, the compound as 100 g and the percentage values of individual Cr2O72- + 14H+ +6e- → 2 Cr3+ +7H2O elements as mass in grams. 10 11th Std Chemistry 001-037.indd 10 23-12-2021 15:03:19  Step 2: Divide the mass of each element 2. An organic compound present in by its atomic mass. This gives vinegar has 40 % carbon, 6.6 % the relative number of moles hydrogen and 53.4 % oxygen. Find the of various elements in the empirical formula of the compound. compound. Simplest ratio Simplest ratio