Do Now: Write the Kc expression for the following CO(g) + H2O(g) ↔ CO2(g) + H2(g) N2(g) + 3H2(g) ↔ 2NH3(g) H2(g) + I2(g) ↔ 2HI(g) 2NO(g) + O2(g) ↔ 2NO2(g) Fe3+(aq) + SCN-(aq) ↔ FeSCN2+(aq)

Kaupapa / Learning Outcome At the end of todays lesson I will be able to discuss the effect on the equilibrium reaction when changes are made to the system.

Equilibrium: Crash Course Chemistry #28

Systems in equilibrium remain unchanged as long as the temperature stays constant

Le Chatelier’s Principle any change made to a system in equilibrium results in a shift of the equilibrium in the direction that minimises the change Page 7

Le Chatelier’s Principle In a nutshell Systems in equilibrium will try and undo any change that you make

Concentration If you increase the concentration of a reactant the equilibrium responds by decreasing the concentration of the reactant by making more products Reactants Products Reactants Products Reactants Products Page 7

If the reaction is exothermic one way it is endothermic the other way Temperature Increasing temperature causes the equilibrium system to decreases the temperature by favouring the endothermic reaction. Decreasing temperature causes the equilibrium to favour the exothermic reaction. If the reaction is exothermic one way it is endothermic the other way Page 8-9

Only effects equilibrium systems with gases. Pressure Increased pressure (by decreasing volume) Pressure is decreased by favouring the side with the least number of gas moles. Decreased pressure (by increasing volume) Pressure is increased by favouring the side with the most number of gas moles. Only effects equilibrium systems with gases. Page 8