1. Dynamic Equilibrium • An equilibrium exists when a reversible reaction reaches a point where the forward and reverse reactions are happening at the same rate • A + B  C + D • Reactants Products 12 Chemistry 2.6 rxn rates, eqm, acids and bases CR 07

2. Dynamic Equilibrium • We call this dynamic equilibrium because there are still forward and reverse reactions happening – the reaction mixture contains both reactants and products. • Even though there is no visible change there is still action = dynamic 12 Chemistry 2.6 rxn rates, eqm, acids and bases CR 07

3. Closed System • To have an equilibrium you must have a closed system – this means that no reactants or products can leave the reaction container 12 Chemistry 2.6 rxn rates, eqm, acids and bases CR 07

4. A + B  C + D • In this equilibrium: • A + B  C + D • C + D  A + B • Both reactions are happening simultaneously 12 Chemistry 2.6 rxn rates, eqm, acids and bases CR 07

5. Dissolving CuSO4 • In a sealed jar CuSO4 crystals dissolve in water to make CuSO4 solution – if the solution is saturated then CuSO4 also comes out of solution 12 Chemistry 2.6 rxn rates, eqm, acids and bases CR 07

6. Forward reaction: • CuSO4(s) + H2O  CuSO4(aq) • Reverse reaction: • CuSO4(aq)  CuSO4(s) + H2O • We write the equilibrium reaction: • CuSO4(s)  CuSO4(aq) 12 Chemistry 2.6 rxn rates, eqm, acids and bases CR 07

7.  •  (double arrow)shows that the reaction is reversible 12 Chemistry 2.6 rxn rates, eqm, acids and bases CR 07

8. In summary • In eqm systems: • The system is closed • There is no observable change • Reactants and products are present • Both forward and reverse reactions are occurring and their rates are equal 12 Chemistry 2.6 rxn rates, eqm, acids and bases CR 07

9. Kc – equilibrium constant • For the equilibrium system: • aA + bB  cC + dD • Kc = [C]c[D]d • _____________ • [A]a[B]b • [ ] = concentration of what is inside the brackets 12 Chemistry 2.6 rxn rates, eqm, acids and bases CR 07