Course Content
Section Name Topic Name 3 Classification of Elements and Periodicity in Properties 3.1 Why do we Need to Classify Elements ? 3.2 Genesis of Periodic Classification 3.3 Modern Periodic Law and the present form of the Periodic Table 3.4 Nomenclature of Elements with Atomic Numbers > 100 3.5 Electronic Configurations of Elements and the Periodic Table 3.6 Electronic Configurations and Types of Elements: s-, p-, d-, f – Blocks 3.7 Periodic Trends in Properties of Elements
Section Name Topic Name 7 Equilibrium 7.1 Equilibrium in Physical Processes 7.2 Equilibrium in Chemical Processes – Dynamic Equilibrium 7.3 Law of Chemical Equilibrium and Equilibrium Constant 7.4 Homogeneous Equilibria 7.5 Heterogeneous Equilibria 7.6 Applications of Equilibrium Constants 7.7 Relationship between Equilibrium Constant K, Reaction Quotient Q and Gibbs Energy G 7.8 Factors Affecting Equilibria 7.9 Ionic Equilibrium in Solution 7.10 Acids, Bases and Salts 7.11 Ionization of Acids and Bases 7.12 Buffer Solutions 7.13 Solubility Equilibria of Sparingly Soluble Salts
Section Name Topic Name 10 The s-Block Elements 10.1 Group 1 Elements: Alkali Metals 10.2 General Characteristics of the Compounds of the Alkali Metals 10.3 Anomalous Properties of Lithium 10.4 Some Important Compounds of Sodium 10.5 Biological Importance of Sodium and Potassium 10.6 Group 2 Elements : Alkaline Earth Metals 10.7 General Characteristics of Compounds of the Alkaline Earth Metals 10.8 Anomalous Behaviour of Beryllium 10.9 Some Important Compounds of Calcium 10.10 Biological Importance of Magnesium and Calcium
Section Name Topic Name 12 Organic Chemistry – Some Basic Principles and Techniques 12.1 General Introduction 12.2 Tetravalence of Carbon: Shapes of Organic Compounds 12.3 Structural Representations of Organic Compounds 12.4 Classification of Organic Compounds 12.5 Nomenclature of Organic Compounds 12.6 Isomerism 12.7 Fundamental Concepts in Organic Reaction Mechanism 12.8 Methods of Purification of Organic Compounds 12.9 Qualitative Analysis of Organic Compounds 12.10 Quantitative Analysis
Class 11th Chemistry Online Class For 100% Result
About Lesson


It covers 71% of earth surface but its distribution is  not uniform.

      That is:- 97.33% Oceans, 2% Polar ice caps and 1% remaining H2O

Physical properties

  1. It is tasteless and odourless liquid.
  2. It freezes to ice at 273K.
  3. Its boiling point is 373K.
  4. Its density is — 1g / cc.

It has  Hydrogen  bonding due to this it  exist as associated molecules. Thereforeit has  high  freezing  Point , high boiling point and  high Heat of vaporisation.That is why, the order for  decrease of these properties is such :

H2O(water)  >  H2S(hydrogen sulpide)  >H2Se(selenium hydride).

  1. It has high thermal conductivity , dipole moment , dilectric constant and high specific heat value.
  2. It is an excellent solvent.
  3. The structure of water is given below :
 Class 11th Chemistry Hydrogen Notes and NCERT Solution
Class 11th Chemistry Hydrogen Notes and NCERT Solution

Chemical properties

  • Reaction with metal : It reacts with metal to form hydroxides and hydrogen gas is released.

         Na    +     H2O  –>       NaOH           + H2

        Sodium      Water   Sodium Hydroxide   Hydrogen Gas

  • Water is amphoteric in nature ,so reacts with acid as well as with base as shown below :
 Class 11th Chemistry Hydrogen Notes and NCERT Solution
Class 11th Chemistry Hydrogen Notes and NCERT Solution

Hardness of water      

Types of water :We have two types of water:

  • Hard : Forms No lather with soap .    

Example : : River water ,sea water etc .

  • Soft : Forms lather with soap .

Example : Rain water

Hardness of water  

It is due to the presence of Calcium and Magnessium  ( Ca2+  and Mg2+ )salts in water . The water with these salts is called as hard water.

The salts basicaly are Magnessium bicarbonates ,sulphates and chlorides or Calcium bicarbonates ,sulphates and chlorides.

Hard water actually contain  Calcium and magnessium salts that react with soap to form insoluble precipitate called scum. It sticks to the cloth .

Therefore ,it cant be used for laundry purpose .

 In Laundry:  The  Soap used is sodium sterate.

Sodium sterate + M2+ à (C17H35 – COO)2 M + 2Na+


Due to formation of  scum lather is not produced with soap.

There are two types of hardness :

  • Temporary: It is due to soluble Ca(HCO3)2 and Mg (HCO3)2  (calcium and magnessium bicarbonates) .           
  • Permanent: It is due to soluble Mg and Ca chlorides and sulphides . 

Methods to remove hardness

     Temporary hardness : It can be removed by following methods :

  • Boiling
  • Clarks method
  • Boiling : In this when we boil hard water, bicarbonates are convereted into hydroxides and calcium bicarbonate is converted into carbonates. These precipitates are filtered and thus, hardness is removed .
  • Clark’s method: In this method calculated amount of lime is added that precipitates Calcium and Magnessium carbonates .
 Class 11th Chemistry Hydrogen Notes and NCERT Solution
Class 11th Chemistry Hydrogen Notes and NCERT Solution
  1. Ion – exchange method

In this a substance called zeolite or permutit is added. This zeolite exchange Sodium with Calcium and Magnessium ions of hard water .

Example of permutit are many like :hydrated Sodium Aluminium Silicates (Na2Al2Si2O8.xH2O)commonly can be indicated as NaZ .

The apparatus is set as shown :

 Class 11th Chemistry Hydrogen Notes and NCERT Solution

Procedure :

  • The zeolite is loosely packed over layers of gravel and sand in big tank .
  • Hard water is introduced from top into the base of tank.
  • From the bottom water rises up through gravel and sand layers.
  • Finally it percolates through the bed of permutit.
  • During this the ions are exchanged .
  • So ,the water above the permutit layer is generally soft water .

Synthetic resin methods are more superior then the ion exchange method as they remove all types of cations and anions and the resultant water is distilled water .

These resins are generally of two types :

  • Cation exchange resin
  • Anion exchnage resin

Cation exchange resin : It consist of giant hydrocarbon framework attached to basic groups . They are represented by general formula R-COOH or R-SO3H .In this R is giant hydrocarbon .These resins can exchange H+ ions with cations present in hard water .

Anion exchange resin : It consist of giant hydrocarbon frmaework attached to basic groups like OH ions, usually in the form of subsituted ammonium hydroxides. They are represented as R-NH3OH where R denotes giant hydrocarbon framework .These resins can exchange hydroxide ion with anions like chloride ions and sulfate ions present in hard water

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