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Predicting Equilibrium
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Determine the reaction quotient, Q, for a system. Include: stating the direction the reaction is proceeding towards equilibrium. Additional KEY Terms
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Reaction quotient (Q) A trial K C that predicts if a reaction has reached equilibrium. Q is calculated exactly like K c U sing the concentrations at that moment. Q is compared to the known reaction Kc. Q indicates which reaction, forward or reverse, must increase (favoured) in reach equilibrium.
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Q = K c The system is AT equilibrium. Forward rate = Reverse rate Concentrations remain constant Q = 5.0 K c = 5.0 Q Reactants Products
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Q > K C The system is NOT at equilibrium. Reverse reaction is favoured (must speed up) Must increase [reactant] Q = 10 K c = 1.0 Q Reactants Products
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Q < K C The system is NOT at equilibrium. Forward reaction is favoured (must speed up) Must increase [product] Q = 0.1 K c = 1.0 Q Reactants Products
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K c = 3.9 x 10 -2 Is the system at equilibrium with: [HI] = 0.75 M[H 2 ] = 0.14 M[I 2 ] = 0.10 M If not, which reaction must continue for equilibrium to be established? 2 HI (g) ↔ H 2 (g) + I 2 (g) Q c = [H 2 ][I 2 ] [HI] 2
![K c = 3.9 x Is the system at equilibrium with: [HI] = 0.75 M[H 2 ] = 0.14 M[I 2 ] = 0.10 M If not, which reaction must continue for equilibrium to be established.](http://images.slideplayer.com./28/9341128/slides/slide_7.jpg "2 HI (g) ↔ H 2 (g) + I 2 (g) Q c = [H 2 ][I 2 ] [HI] 2.")
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Q C = 2.5 x 10 -2 K C = 3.9 x 10 -2 Q < K The system is NOT at equilibrium. Forward reaction is favoured – must continue Must increase [product] Q c = [0.14][0.10]= 2.5 x 10 -2 [0.75] 2 [H 2 ][I 2 ] [HI] 2 QcQc =
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Initially 6.0 mol of SO 2, 3.0 mol of O 2 are mixed in a 1.0 L reaction container. At equilibrium, 0.50 mol of O 2 are found to remain. Is this system at equilbrium? K c = 5.6 x 10 -3 2 SO 3 (g) 2 SO 2 (g) + O 2 (g) [E][E] 1.0 M 0.50 M 5.0 M [I][I] 06.0 M3.0 M [C][C] - 5.0 + 5.0- 2.5 K c = [SO 2 ] 2 [O 2 ] [SO 3 ] 2
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Q c = 0.02 [E][E] 1.00.505.0 Q c = [SO 2 ] 2 [O 2 ] [SO 3 ] 2 2 SO 3 (g) 2 SO 2 (g) + O 2 (g) Q c = [1.0] 2 [0.50] [5.0] 2 Q > K NOT at equilibrium. Reverse reaction is favoured [products] are decreasing, [reactants] increasing
![Q c = 0.02 [E][E] Q c = [SO 2 ] 2 [O 2 ] [SO 3 ] 2 2 SO 3 (g) 2 SO 2 (g) + O 2 (g) Q c = [1.0] 2 [0.50] [5.0] 2 Q > K NOT at equilibrium.](http://images.slideplayer.com./28/9341128/slides/slide_10.jpg "Reverse reaction is favoured [products] are decreasing, [reactants] increasing.")
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CAN YOU / HAVE YOU? Determine the reaction quotient, Q, for a system. Include: stating the direction the reaction is proceeding towards equilibrium. Additional KEY Terms
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