Lee chetlier's principle in this lecture I will teach you my personal trick of leecher clear's principle I challenge you that you will not find this trick in any book or in any video format so watch this lecture till the end and you will learn something very easy about Lee chetlier's principle firstly let me teach you the easy concept of chemical equilibrium let's consider an atom X and an atom y now X and Y atoms react together to form X Y molecule while this X5 molecule breaks down to form X atom and Y atom so this is a reversible reaction lastly when the speed or rate of our reaction will become equal to the speed or rate of backward reaction this stage is called chemical equilibrium hence this reaction is in chemical equilibrium because the speed of forward reaction is equal to the speed of backward reaction here let me ask you one important question which I often ask what is meant by disturbing chemical equilibrium well when we say disturbing chemical equilibrium it means that we are disturbing or changing the speed of either forward reaction or backward reaction so remember that whenever I say disturbing the chemical equilibrium it means that I am disturbing the speed of either side now the second question is how can we disturb the chemical equilibrium basically there are three methods through which we can disturb any chemical equilibrium firstly change the concentration of reactants in products secondly changing the temperature of a system and thirdly changing the pressure of a system thus remember that we can disturb the chemical equilibrium by three different ways now what is leachatier's principle in simple words well consider the previous example let this reaction is in chemical equilibrium now I am interested to disturb the chemical equilibrium let's consider that I add one another atom of X and one another atom of Y so I have changed the concentration of reactants now this system will respond to this change of concentration of reactants let me repeat it this system will respond to this change of concentration of reactants here the change is simple I mean the concentration of reactants is large and the concentration of product is small so what will be the response of this system it is very simple the rate of forward reaction will become High to make more products now the rate of forward direction is higher than the rate of backward reaction or we say that equilibrium is shifted in forward Direction lastly when two molecules are completely formed the system will restore its chemical equilibrium I mean the rate of forward reaction becomes equal to the rate of backward reaction because for atoms react together to form two molecules and two molecules break down to form four atoms now listen carefully overall we learned that if we disturb the chemical equilibrium of a reversible reaction it will respond to the change and will restore its chemical equilibrium let me repeat it if we disturb the chemical equilibrium of a reversible reaction it will respond to the change and will restore its chemical equilibrium this is what the leachatelier's principles state so note it down this super easy definition of leachate layers principle which is often made very difficult now let me teach you my personal trick of leechette layer's principle for example consider this reversible reactions now what will happen if we increase the concentration of hydrogen gas in this case and decrease the concentration of nitrogen gas in this case well I use my personal trait let X atom and Y atom react together to form X Y molecule and X Y molecule breaks down to form X Y atoms now listen carefully when we increase the concentration of hydrogen gas it means that we are adding more hydrogen gas here if I ask you what is changed your answer is simple there are more reactants and less product secondly if I ask you what is the response of this system your answer is again simple the equilibrium will proceed in forward direction to form more products and neutralize the effect of concentration let me repeat it the equilibrium will proceed in forward direction to form more products and neutralize the effect of concentration therefore remember that if we increase the concentration of the hydrogen gas equilibrium will shift in forward direction to neutralize the effect and restore chemical equilibrium secondly I again write X and Y atoms they react together to form X Y molecule now listen carefully when we decrease the concentration of nitrogen gas it means that we are reducing or removing nitrogen gas here if I ask you what is changing and what is the response of the system your answer is simple there are more products and less reactants secondly the equilibrium will proceed in backward Direction in order to form more reactants and neutralize the effect therefore if we decrease the concentration of nitrogen gas equilibrium will shift in backward direction to neutralize the effect and restore chemical equilibrium thus using this tray we can easily calculate the equilibrium shift if concentration is changed now let me teach you the effect of changing pressure on chemical equilibrium here remember that changing pressure only affects reversible reactions F reactants and products are in gaseous State now consider these reactions what will happen if we increase the pressure in this case and decrease the pressure in this case well on the left side there is one mole of pcl5 while on the right side there is one mole of pcl3 and one mole of chlorine gas so I write one mole of reactants and two moles of products now here the trick is that we only consider larger number we can see that the larger number is 2 mole now listen carefully when we increase the pressure it means that we are increasing the number of 2 moles further and putting more pressure let me repeat it when we increase the pressure it means that we are increasing the number of two moles further and putting more pressure so here the change is more pressure on products and less pressure on reactants can you guess the response of this system well it is simple the equilibrium will proceed in backward direction to counter the effect of pressure and restore chemical equilibrium secondly in this case we already know that there is one mole of reactants and there are two moles of products we know that we only consider the larger number here the larger number is 2. now when we decrease the pressure it means that we are decreasing the number of 2 moles further and putting less pressure on reactants let me repeat it when we decrease the pressure it means that we are decreasing the number of 2 moles further and putting less pressure on reactants so here the change is less pressure on products and more pressure on reactants thus the response will be the equilibrium will proceed in forward direction to counter the effect of pressure therefore remember that decreasing pressure means that equilibrium will shift in forward Direction so using this simple trick we can easily calculate the effect of change of pressure on chemical equilibrium here let me teach you one bonus question consider this reversible reaction what will be the effect of increasing or decreasing pressure well the answer is simple increasing or decreasing pressure has no effect on this chemical reaction because the number of moles of reactants is 2 and the number of moles of products is also two so note it down that if the number of moles of reactants is equal to the number of moles of products changing pressure doesn't affect the chemical equilibrium finally let me teach you the effect of changing temperature on chemical equilibrium remember that if heat of enthalpy Del H is negative it is an exothermic reaction and which heat is given off to the surrounding while if heat of enthalpy Del H is positive it is an endothermic reaction in which heat is absorbed from the surrounding now consider these reversible reactions what will happen if we decrease temperature in this case and increase temperature in this case well we know that this is endothermic reaction in case of endothermic reaction I always write here cold and I write here hard here the trick is we only consider the hot side and we do not look at the cold side now listen carefully if we decrease the temperature it means that we are are cooling the hot side are removing heat from the hot side let me repeat it if we decrease the temperature it means that we are cooling the hot side or removing heat from the hot side so the change is product becomes cold and reactants become hot now the response is equilibrium will proceed in forward Direction in order to produce more reactants to counter the effect of temperature secondly in this case we know that the enthalpy of heat is negative so it is an exothermic reaction in case of exothermic reaction I always write here hot and I write here called now listen carefully if we increase the temperature it means that we are adding more heat to the hot side let me repeat it if we increase the temperature it means that we are adding more heat to the hot side so the change is reactant becomes hot and products become cold thus the response of the system will be equilibrium milk shift in forward Direction in order to produce more products to counter the effect of temperature therefore if we increase the pressure the equilibrium will shift in forward Direction Just note it down these examples last lastly let me teach you one bonus question why adding Catalyst cannot affect the position of equilibrium well it is because the Catalyst speeds up the forward and the backward reaction to the same extent so adding Catalyst only speeds up the forward and backward reaction it doesn't change the position of equilibrium I hope that you have learned all about Lee chatelier's principle