Le-chatlier Principle
Defination: If you imppose a change on a system that is at equilibrium system behave in a way as to oppose that change.
Change in concentration :If concentration of reactant is increased reaction will move in farward direction towards product to nuteralize the effect of that change.
If concentration of product is increased reaction will move in backward direction. For example consider a reversable reaction
H2 + I2 <=====> 2HI
In this reaction if concentration of Hydrogen and Iodine is increased reaction will move in farward direction.
Change in pressure :
If pressure is increased reaction will move towards less volume side (less no of mole side).If pressure is decreased reaction will move towards greater volume side(more no of mole side).
N204 <=====> 2NO2 H= +57.2
In this reaction prooduct have 2 moles and reactant have 1 mole since volume is directly proprtional to no of moles and inversly proportional to pressure .hence increase in pressure will move reaction towards backward direction.
If no of moles of both ractant and product are same pressure change will not effect eqilibrium .
H2 + I2 <=====> 2HI
Change in Temperature:
Reaction is of two types exothermic (Heat is released -ve sign) or endothermic (heat is absorbed+ve sign).
If reaction is exothermic increase in temperature will move reaction in backward direction and vice versa
If reaction is endothermic Increase in temperature will favour farward reaction .
For example consider the following reaction
N204 <=====> 2NO2 H= +57.2
+ve sign show it is an endothermic reaction.If we increaese temperature reaction will move in farward direction.
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