What is Le Chatelier’s principle?
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Explanation:
also called Chatelier's principle or "The Equilibrium Law", can be used to predict the effect of a change in conditions on some chemical equilibria. The principle is named after Henry Louis Le Chatelier and sometimes Karl Ferdinand Braun who discovered it independently.
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What are Le Chatelier’s Principles?
Le Chatelier’s principles, also known as the equilibrium law, are used to predict the effect of some changes on a system in chemical equilibrium (such as the change in temperature or pressure). The principle is named after the French chemist Henry Louis Le Chatelier.
Le Chatelier said that equilibrium adjusts the forward and backward reactions in such a way to accept the changes affecting the equilibrium conditions.
Table of Content
Effect of Concentration Changes
Effect of Change of Volume, Pressure
Effect of Temperature Changes
Effect of Catalyst
When factors like concentration, pressure, temperature, inert gases that affect equilibrium are changed, the equilibrium will shift in that direction where the effects caused by these changes are nullified.
Le Chatelier’s principles are often used to manipulate reversible reactions in order to obtain suitable outcomes (such as an improvement in yield).
Effect of Concentration Changes on Equilibrium and Product Formation
As per Le Chatelier’s principles, the only way of equilibrium to accept more reactant is to increase product formation.
Similarly, the addition of product (concentration/pressure) shall increase the backward reaction to decrease the product concentration.
Also Read:
Chemical Equilibrium
Ionic Equilibrium – Degree of Ionization and Dissociation
Equilibrium Constant – Characteristics and Applications
Effect of Change of Volume, Pressure, or Inert Gas on Equilibrium and Product Formation
Kp = Kc (RT)Δn = Kc (p/v)Δn
Change of volume, pressure, or inert gases has no effect on reactions of liquids and solids. They may have an effect in gaseous reactions and that too only when the difference in the sum of the number of reactant and product molecules (∆n) is not zero.
When ∆n = 0:
As per the Le Chatelier’s principles, there will be no effect on Equilibrium and Product Formation on changing the volume, pressure or inert gas.
When ∆n = +ve:
Increase of pressure or decrease in volume will decrease the formation of the product. Decrease of pressure or increase of volume shall have the opposite effect of increasing the product formation.
Inert gases do not take part in the reaction and shall increase the volume or pressure only.
At constant pressure, the addition of inert gas increases the volume, so increase the product formation.
At constant volume, the addition of inert gas increases the pressure, so decreases the product formation.
PCl5 ⇌ PCl3 + PCl2
In the decomposition of phosphorus pentachloride ∆n = +1.
Increase of pressure or decrease in volume decreases the decomposition of PCl5
At constant pressure, the addition of inert gas increases the PCl5 formation.
At constant volume, the addition of inert gas decreases the PCl5 formation.
When ∆n = -ve:
As per Le Chatelier’s principle, an increase of pressure or decrease in volume will increase the formation of the product.
At constant pressure, the addition of inert gas increases the volume, so decrease the product formation.
At constant volume, the addition of inert gas increases the pressure, so increases the product formation
N2 + 3H2 ⇌ 2NH3
In the formation of ammonia ∆n = -2. The increase of pressure or decrease in volume increases the formation of ammonia.
At constant pressure, the addition of inert gas decreases ammonia formation.
At constant volume, the addition of inert gas increases ammonia formation.
Effect of Change of Temperature on Equilibrium and Product Formation
The individual reaction in the equilibrium can be either endothermic or exothermic. Likewise, at equilibrium net energy involved may make the reversible reactions either endothermic or exothermic.
According to Le Chatelier’s Principles,
In exothermic equilibrium, an increase in temperature decreases the product formation and decrease in temperature increases product formation.
In endothermic reactions, an increase in temperature increases the product formation and decrease in temperature decreases the product formation
Le Chatelier’s principles, also known as the equilibrium law, are used to predict the effect of some changes on a system in chemical equilibrium (such as the change in temperature or pressure). The principle is named after the French chemist Henry Louis Le Chatelier.
Le Chatelier said that equilibrium adjusts the forward and backward reactions in such a way to accept the changes affecting the equilibrium conditions.
Table of Content
Effect of Concentration Changes
Effect of Change of Volume, Pressure
Effect of Temperature Changes
Effect of Catalyst
When factors like concentration, pressure, temperature, inert gases that affect equilibrium are changed, the equilibrium will shift in that direction where the effects caused by these changes are nullified.
Le Chatelier’s principles are often used to manipulate reversible reactions in order to obtain suitable outcomes (such as an improvement in yield).
Effect of Concentration Changes on Equilibrium and Product Formation
As per Le Chatelier’s principles, the only way of equilibrium to accept more reactant is to increase product formation.
Similarly, the addition of product (concentration/pressure) shall increase the backward reaction to decrease the product concentration.
Also Read:
Chemical Equilibrium
Ionic Equilibrium – Degree of Ionization and Dissociation
Equilibrium Constant – Characteristics and Applications
Effect of Change of Volume, Pressure, or Inert Gas on Equilibrium and Product Formation
Kp = Kc (RT)Δn = Kc (p/v)Δn
Change of volume, pressure, or inert gases has no effect on reactions of liquids and solids. They may have an effect in gaseous reactions and that too only when the difference in the sum of the number of reactant and product molecules (∆n) is not zero.
When ∆n = 0:
As per the Le Chatelier’s principles, there will be no effect on Equilibrium and Product Formation on changing the volume, pressure or inert gas.
When ∆n = +ve:
Increase of pressure or decrease in volume will decrease the formation of the product. Decrease of pressure or increase of volume shall have the opposite effect of increasing the product formation.
Inert gases do not take part in the reaction and shall increase the volume or pressure only.
At constant pressure, the addition of inert gas increases the volume, so increase the product formation.
At constant volume, the addition of inert gas increases the pressure, so decreases the product formation.
PCl5 ⇌ PCl3 + PCl2
In the decomposition of phosphorus pentachloride ∆n = +1.
Increase of pressure or decrease in volume decreases the decomposition of PCl5
At constant pressure, the addition of inert gas increases the PCl5 formation.
At constant volume, the addition of inert gas decreases the PCl5 formation.
When ∆n = -ve:
As per Le Chatelier’s principle, an increase of pressure or decrease in volume will increase the formation of the product.
At constant pressure, the addition of inert gas increases the volume, so decrease the product formation.
At constant volume, the addition of inert gas increases the pressure, so increases the product formation
N2 + 3H2 ⇌ 2NH3
In the formation of ammonia ∆n = -2. The increase of pressure or decrease in volume increases the formation of ammonia.
At constant pressure, the addition of inert gas decreases ammonia formation.
At constant volume, the addition of inert gas increases ammonia formation.
Effect of Change of Temperature on Equilibrium and Product Formation
The individual reaction in the equilibrium can be either endothermic or exothermic. Likewise, at equilibrium net energy involved may make the reversible reactions either endothermic or exothermic.
According to Le Chatelier’s Principles,
In exothermic equilibrium, an increase in temperature decreases the product formation and decrease in temperature increases product formation.
In endothermic reactions, an increase in temperature increases the product formation and decrease in temperature decreases the product formation
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