Chemistry

le Chatelier’s Principle Statement and Different Effects

Statement of Le Chatelier’s Principle: “When a constraint or stress in a direction is applied to a system in equilibrium, the equilibrium position changes so as to undo the constraint”.

Or

“If a system in equilibrium is altered by changing concentration, pressure or temperature, the equilibrium shifts in direction that minimize or undo the effect of the change”.

Or

“If a system at equilibrium disturbed by some change, the system will shift so as to neutralize the effect of change”.

  1. Effect of concentration change using Le Chatelier’s Principle

Change in concentration is directly affected by equilibrium. If the concentration of the reactant increase, the equilibrium is disturbed. According to the Le-Chatelier’s Principle, equilibrium will shift to the right to keep the value of ‘Kc’ constant and as a result of this more product is formed.

If the concentration of the product increases, the equilibrium is disturbed. According to Le-Chatelier’s principle, equilibrium will shift to the left to keep the value of ‘Kc’ constant and a result of this concentration of reactant increases.le Chatelier's Principle

  1. Effect of Temperature Change on Le Chatelier’s Principle

There are two types of chemical reaction:

  1. The exothermic reaction, in which heat is evolved and it is favoured in low temperature.
  2. The endothermic reaction, in which heat is absorbed and it is favoured in high temperature.

Le Chatelier’s Principle For Exothermic Reaction

According to Le-Chatelier’s principle, if the temperature is decreased in an exothermic reaction the equilibrium shift from forwarding direction and as a result of this more products is formed. And with the rise in temperature, the equilibrium will shift towards backward direction and the concentration of product is decreased.

For Endothermic Reaction

According to Le-Chatelier’s principle, if the temperature is decreased in an endothermic reaction the equilibrium shift from backward direction and a result of this concentration of products is decreasing. And with the rise in temperature, the equilibrium will shift from the forward direction and the concentration of product is increased.

  1. Effect of Pressure Change

Change in pressure only affects gaseous equilibrium because the change in pressure is related to the change in volume. Pressure has no effect on solids and liquids because they are almost incompressible, hence their volumes are very little affected by the change in pressure.

  1. Effect of Catalyst using Le Chatelier’s Principle

A catalyst has no effect on the equilibrium. It increases the rate of reaction by lowering the energy of activation and enables equilibrium to be reached more quickly.

learn Le Chatelier’s Principle through video

References:

https://en.wikipedia.org/wiki/Le_Chatelier%27s_principle

https://www.chemguide.co.uk/physical/equilibria/lechatelier.html

https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Equilibria/Le_Chatelier’s_Principle

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch16/lechat.html

https://www.cliffsnotes.com/study-guides/chemistry/chemistry/equilibrium/le-chateliers-principle

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