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Predicting Equilibrium

Predicting Equilibrium. Determine the reaction quotient , Q, for a system. Include: stating the direction the reaction is proceeding towards equilibrium. Additional KEY Terms. Reaction quotient (Q) A trial K C that predicts if a reaction has reached equilibrium.

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Predicting Equilibrium

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  1. Predicting Equilibrium

  2. Determine the reaction quotient, Q, for a system. • Include: stating the direction the reaction is proceeding towards equilibrium. Additional KEY Terms

  3. Reaction quotient (Q) A trial KCthat predicts if a reaction has reached equilibrium. • Q is calculated exactly like Kc • Using the concentrations at that moment. • Qis compared to the knownreaction Kc. • Qindicateswhich reaction, forward or reverse, must increase (favoured) in reach equilibrium.

  4. Q Kc = 5.0 Reactants Products Q = 5.0 • Q = KcThe system is AT equilibrium. • Forward rate = Reverse rate • Concentrations remain constant

  5. Q Kc = 1.0 Reactants Products Q = 10 • Q > KC The system is NOT at equilibrium. • Reverse reaction is favoured (must speed up) • Mustincrease[reactant]

  6. Q Kc = 1.0 Reactants Products Q = 0.1 • Q < KCThe system is NOT at equilibrium. • Forward reaction is favoured (must speed up) • Mustincrease[product]

  7. 2 HI(g) ↔ H2 (g) + I2 (g) [H2][I2] Qc = Kc = 3.9 x 10-2 Is the system at equilibrium with: [HI] = 0.75 M [H2] = 0.14 M [I2] = 0.10 M If not, which reaction must continue for equilibrium to be established? [HI]2

  8. Qc = [0.14][0.10] = 2.5 x 10-2 [0.75]2 [H2][I2] Qc = • QC = 2.5 x 10-2KC = 3.9 x 10-2 • Q < K • The system is NOT at equilibrium. • Forward reaction is favoured – must continue • Mustincrease[product] [HI]2

  9. 2 SO3 (g) 2 SO2 (g) + O2 (g) Kc = [SO2]2[O2] Initially 6.0 mol of SO2, 3.0 mol of O2 are mixed in a 1.0 L reaction container. At equilibrium, 0.50 mol of O2 are found to remain. Is this system at equilbrium? Kc= 5.6 x 10-3 0 6.0 M 3.0 M [I] - 5.0 [C] + 5.0 - 2.5 0.50 M 5.0 M 1.0 M [E] [SO3]2

  10. 2 SO3 (g) 2 SO2 (g) + O2 (g) Qc = Qc = [SO2]2[O2] [1.0]2[0.50] 5.0 1.0 0.50 [E] Q > K NOT at equilibrium. Reverse reaction is favoured [products] are decreasing, [reactants] increasing Qc = 0.02 [SO3]2 [5.0]2

  11. 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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