Le Châtelier’s principle The significance of Kc values • Read 14.6 (560 - 561) do PE5 If Kc is small (0.001 or lower), [products] must be small, thus forward reaction is weak If Kc is large (1000 or more), [products] must be large, thus forward reaction is strong [Products] Kc = [Reactants] Reactants ↔ Products If Kc is about 1, then reactants and products are about equal but not exactly since they may be raise to different exponents Altering the straw lab • Recall the lab with large and small straws Q - Predict what will happen when: 5 ml is added to GC2 at 15 transfers, and then 10 ml is removed from GC1 at 20 transfers • The volumes stopped changing at 30, 20 mL Volume # of transfers 15 20 30 20 Stresses to equilibria • Changes in reactant or product concentrations is one type of “stress” on an equilibrium • Other stresses are temperature, and pressure. • The response of equilibria to these stresses is explained by Le Chatelier’s principle: If an equilibrium in a system is upset, the
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