CHM1046 LECTURE NOTES 14 7 The Reaction Quotient Q aA bB cC dD Q C c D d A a B b Qp P C c P D d P A a P B b P is the pressure at anytime of the reaction if Q K the reaction is at equilibrium if Q K the reaction proceeds to the left to reach equilibrium if Q K the reaction proceeds to the right to reach equilibrium Do example 14 7 in the book for practice 14 9 Le Chatelier s principle states that when a chemical system is disturbed the equilibrium shifts in a direction that minimizes the disturbance What disturbs equilibrium 1 Concentration change 2 Pressure or volume change 3 Temperature change need to know if reaction is endothermic or 1 Effect of Concentration Change on equilibrium exothermic N2O4 g 2NO g If after reaching equilibrium more NsO4 was added to the system what will happen The system will shift right to consume some of the excess NsO4 If NO2 is added to the system it will shift left to consume some of the excess NOs If some NO2 was collected taken from the system the system will shift right to consume some of the excess NO2 to produce more NOs 2 Effect of Pressure or Volume change N2 g 3H2 g 2NH3 g What happens if the pressure of the system is reduced if the pressure is reduced the system will want to increase the pressure so it will shift to the side with more gas molecules in this case that would be a shift to the left What happens if the pressure is increased if the pressure is increased the system will want to decrease the pressure by shifting to the side with less gas molecules in this case it would shift to the right to produce less gas molecules which will lead to a decrease in pressure Volume changes have an inverse effect to pressure changes If volume increases pressure decreases and if pressure increases volume decreases 3 Effect of temperature change N2 g 3H2 g 2NH3 g H 0 so exothermic reaction N2 g 3H2 g 2NH3 g heat What happens if the temperature is increased the system will shift in this case to the left to consume some of the excess heat system will shift to side opposite from where heat is being added
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