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: Elevate Your CBSE Board Success
About Lesson

Law of mass action

It states that: Rate of a reaction is directly proportional to concentration of reactants raised to their respective moles.

Consider a reaction: aA + bB –> cC + dD

According to this law:

At equilibrium: Rate of forward reaction = rate of backward reaction

That is: Kf[A]a[B]b = Kb[C]c[D]d

But, Kc=Kf/Kb (where Kc is equilibrium constant)

Kc = [A]a[B]b/[C]c[D]d

At particular instant of time: The equilibrium constant is called as reaction quotient (Q).

That is: Q=[C]c[D]d /  [A]a[B]b

At equilibrium Q=Kc

For example:

Equilibrium notes class 11 and ncert solution for excel in the exam
equilibrium notes class 11

Please note:

  • If change in gaseous moles=0 then kp = kc
  • If change in gaseous moles is greater than 1 ,then Kp= kRT or kp > kc
  • If change in gaseous moles is less than zero, then kp < kc

Characteristics of Equilibrium constant (k)

  1. Its value depends upon temperature and is independent of concentration of reactants or products, with which we start reaction.
  2. If the reaction reverses, the value of k also gets reversed.

For example: If for forward reaction k =4 then, on reversing the value of k will be ¼ .

  1. If whole reaction is divided by 2, then the value of k also gets root of K.
  2. If whole reaction is multiplied by 2, then value of k also gets multiplied by the same number 2 or 3 i.e Kn.
  3. If the reaction takes place in two or more steps, then the value of k for complete reaction is given by k=k1.k

Characteristics of chemical equilibrium

  1. The Rate of forward reaction = Rate of reverse reaction.
  2. Catalyst does not affect the equilibrium .It just helps to achieve equilibrium faster.
  3. The Equilibrium is attained only is closed vessel.
  4. Equilibrium can be achieved from either direction.
  5. At equilibrium concentration of reactants and products becomes equal.

Effect of temperature on K

We know that K=Kf/Kb

Now if temperature is increased, then the rate of reaction also increases. The extent of reaction depends upon activation energy of reactants i.e Rf and Rb will be different and also the value of Kf and Kb .So, the value of K will also change.

  • For endothermic reactions: Kf>Kb. Therefore, K increases.
  • For exothermic reactions: Kf<kb .Therefore, K decreases.

Units of k

Kc = (mol/L)change in gaseous moles

Kp = (atm)change in number of gaseous moles

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