Equilibrium Class 11 Notes

Equilibrium Class 11

Equilibrium is an important topic in class 11 chemistry syllabus and can also be a very scoring one if you study properly and all your concepts are clear. It is a vast chapter and contains many significant concepts such as buffer solutions, equilibrium constants and many more. Here, through this blog, we aim to provide you with notes related to Equilibrium class 11 and clear all your doubts. 

Must Read: Class 11 Hydrogen Notes


Before we go into further details in equilibrium class 11 chapter, we must know what exactly is equilibrium. Equilibrium is achieved when the molecules exiting the liquid to the vapour are equivalent to the molecules coming from the vapour to the liquid. Kc is the constant of equilibrium. It is determined by the concentration of products divided by the concentration of reactants in which each term is increased to the stoichiometric coefficient. 

At equilibrium, Rate of the forward reaction = Rate of the backward reaction

which is rf = rb Or, kf × α × [A]a[B]b =  kb × α × [C]c [D]d

where , rf = rate of forward reaction

What is Chemical Equilibrium?

Chemical Equilibrium is essential in many biochemical processes and the environmental system. For example, balancing involves O2 molecules and protein haemoglobin which also play an important role in the transportation of O2 from our body to the lung muscles. Related balances of CO molecules and haemoglobin are responsible for the degradation of CO. Remember this definition in the Equilibrium Class 11 notes which are really important. 

Also Read: Chemical Bonding and Molecular Structure Class 11 Study Notes

Law of Chemical Equilibrium

We move on further to the Law of Chemical Equilibrium in equilibrium class 11. The Law of Chemical Equilibrium states that at a constant temperature, the rate of a chemical reaction is directly proportional to the molar concentration of the reactants, that are each increased to a power equal to the respective stoichiometric coefficients defined by the balanced chemical equation. For example:

Equilibrium Class 11 - Laws of Chemical Equilibrium
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Types of Chemical Equilibrium

Equilibrium class 11 talks about the various kinds of chemical equuilibrium. There are two types of chemical equilibrium present which are known as:

  • Homogeneous Equilibrium
  • Heterogeneous Equilibrium

Homogeneous Chemical Equilibrium 

In Homogeneous Equilibrium, the reagents and the chemical balance products are all in the same process. Homogenous balance can be further classified into two types: reactions in which the number of molecules of the compounds is equal to the number of molecules of the reactants. For instance, 

H2 (g) + I2 (g) 2HI (g) 

N2 (g) + O2 (g) No 2NO (g)

Heterogeneous Chemical Equilibrium 

In Heterogeneous Equilibrium, the reagents and chemical balance products are present in various phases. Here is an instance of heterogeneous equilibrium. 

CO2 (g) + C(s) No 2CO (g)

Why is Chemical Equilibrium Also Known As Dynamic Equilibrium? 

Next in equilibrium class 11 is the other name of chemical equilibrium, which is dynamic equilibrium. The point at which the rate of forward reaction is equal to the rate of backward reaction is considered the level of equilibrium. At this point, the amount of reagent molecules that transform into products or product molecules into reagents will be the same. The very same equilibrium can be performed with the same reagents everywhere under identical conditions with continuous molecular exchange, hence the chemical equilibrium is dynamic.

Importance of Chemical Equilibrium 

Equilibrium class 11 talks about the importance of chemical equilibrium. It is useful in many manufacturing processes, such as 

  • Preparation of ammonia by Haber’s process: in this nitrogen it mixes with hydrogen to produce ammonia, the production of ammonia is higher at low temperature, high pressure and in the presence of iron as a catalyst. 
  • Preparation of sulphuric acid by contact process: the basic mechanism in this method is the transformation of sulphur dioxide into sulphur trioxide. This requires chemical equilibrium.

Characteristics of Equilibrium Involving Physical Processes  

Here are some of the characteristics of Equilibria which involve physical processes which is an important topic for Equilibrium Class 11:

  1. Equilibrium can only be maintained in closed systems at a given temperature. The observable features of the system remain stable at equilibrium. 
  2. Balance is complex, as both forward and backward processes operate at the same time. 
  3. At equilibrium, concentrations of compounds become stable at constant temperatures. 
  4. The quality of the constant equilibrium is the degree to which the mechanism continues before the equilibrium is reached.

Le Chatelier’s Principle 

It implies that the change of some factor, such as concentration, strain, temperature, etc., causes the balance to move in that direction in order to offset or decrease the influence of the change. This famous principle is named after the French chemist who was Henry Louis Le Chatelier.The effects that are described by him are:

  • Effect of changes in concentration 
  • Effect of Volume Transition, Pressure 
  • Effect of variations in temperature 
  • Effect of Catalyst 

As variables such as concentration, pressure, temperature, inert gases, which influence balance, change, the balance shifts in that direction where even the effects induced by these changes are nullified. 

Le Chatelier’s ideas are also used to influence reversible responses in order to produce acceptable results (such as an improvement in yield)  and it is very important chapter for Equilibrium Class 11.


Electrolytes are defined as the compounds that conduct electricity in aqueous solutions. Examples of electrolytes involve bases, salts, and acids. Electricity in aqueous solution is caused by cations and anions formed by the ionisation or dissociation of electrolytes which are present in the solution. 

Explore: Structure of Atom Class 11 Notes

We hope that our Equilibrium Class 11 notes were helpful for your learning and assist you in acing your exams. Check out our page, Leverage Edu for more Class 11 Notes on various subjects to help you in scoring great marks!

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