1. K c and equilibrium

2. What does K c signify? If K c = 1 then the position of equilibrium is half way between products and reactants If K c > 1 then the equilibrium lies to the right. If K c < 1 then the equilibrium lies to the left.

3. Week 18 © Pearson Education Ltd 2009 This document may have been altered from the original When K c >> 1 equilibrium lies to the right

4. Week 18 © Pearson Education Ltd 2009 This document may have been altered from the original When K c << 1 equilibrium lies to the left

5. Temperature and K c Increasing temperature shifts the equilibrium to the endothermic direction (ΔH +ve) Decreasing temperature shifts the equilibrium to the exothermic direction (ΔH –ve) Changing the position of the equilibrium actually depends on the value for K c, which only changes it’s value only with changes in temperature.

6. Week 18 © Pearson Education Ltd 2009 This document may have been altered from the original Ammonia equilibrium

7. Changing Concentration Changing the concentration of a reactant or product doesn’t change the K c value. Changing the concentration will force the equilibrium to move in accordance to le Chatalier’s principle.

8. Changing Pressure Similarly changing pressure doesn’t change the value of K c. The equilibrium shifts to return the reaction to the equilibrium point.

9. Catalysts Catalysts do nothing. They speed up both reactions equally, so don’t affect the value of K c.

10. Remember! Rate constants tell us how FAST a reaction is. – Calculated from experimental data Equilibrium constants tell us how far a reaction can go – Calculated from an overall balanced equation.