14 9 Le Chatelier s Principle When a chemical system is disturbed the equilibrium shifts in a direction that minimizes the disturbance What disturbes an equilibrium Concentration changes of reactants or products Pressure or Volume changes Temperature changes EFFECT OF CONCENTRATION CHANGES ON EQUILIBRIUM N2O4 g 2NO2 g If more N2O4 is added the system would shift to the right where N2O4 is a reactant in order to try and consume some of the excess N2O4 so the system could remain at equilibrium If more NO2 is added the system would shift to the left where NO2 is a reactant when the reaction is proceeding towards the left to try to consume some of the excess NO2 and remain at equilibrium If some NO2 is taken out of the system the system would shift to the right where NO2 is a product to produce more NO2 and remain at equilibrium EFFECT OF PRESSURE OR VOLUME CHANGES ON EQUILIBRIUM N2 g 3H2 g 2NH3 g there are 4 gas molecules on the left and 2 gas molecules on the right If the pressure in the system is decreased the system would shift to the side where more gas molecules are being produced the left to increase the pressure If the pressure is increased the system will shift to the right or the side where less gas molecules are being produced to decrease the pressure Volume changes have the opposite effect of pressure changes because when volume is decreased the pressure in a system increases And when volume is increased molecules spread out and the pressure in a system decreases If the volume is increased it would have the same effect as when the pressure is decreased Meaning the reaction would shift to the left If the volume is decreased it would have the same effect as when pressure is increased Meaning the reaction will shift to the right EFFECT OF TEMPERATURE CHANGES ON EQUILIBRIUM N2 g 3H2 g 2NH3 g heat exothermic giving off heat If temperature is increased or heat is added the system will try to consume some of the excess heat and shift to the left where heat is a reactant If temperature is decreased or heat is taken away the system will try to produce more heat and shift to the right where heat is a product
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