CHM1046 LECTURE NOTES14.7The Reaction Quotient, Q:aA + bB cC + dDQ= [C]c[D]d/ [A]a[B]bQp = 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)14.9Le Chatelier’s principle:-states that when a chemical system is disturbed, the equilibrium shifts in a direction that minimizes the disturbanceWhat disturbs equilibrium?1. Concentration change2. Pressure (or volume) change3. Temperature change (need to know if reaction is endothermic or exothermic)1. Effect of Concentration Change on equilibrium: 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 excessNOs- If some NO2 was collected (taken) from the system, the system will shift right to consume some of the excess NO2 to produce more NOs2. 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 decreases3. Effect of temperature change:N2 (g) + 3H2 (g) 2NH3 (g)(ΔH<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
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