The student will learn: 1. Using LeChatelier’s principles be able to predict production of the reaction based on the stress placed upon a reaction

Two opposing changes occur at ‘equal rates’ Reversible reaction A chemical reaction in which the products can react to form the reactants. Examples in your life : baby make-up, match box cars, pencils, shirts, prescription sunglasses. Equilibrium: Two opposing changes occur at ‘equal rates’ Q: When is a reaction that is reversible considered to have reached equilibrium? A: When forward reaction rate = reverse reaction rate. Caution:: Equilibrium….equal… it may appear all has stopped but not so……. Very dynamic, frantic activity, not static.

Closed system: Matter can not enter or exit. Reaction Equilibrium Closed system: Matter can not enter or exit. “ but energy can” example: sunlight, heat from a burner, cooling by ice Le Chatelier’s Principle: if a system at equilibrium is subjected to a stress then the reaction will be shifted in the direction to relieve the stress. We will learn 4 stress effects : change in pressure change in temperature change in concentration adding a catalysts

3H2 (g) + N2 (g) 2NH3 (g) + heat C (s) + H2 (g) + heat CO (g) + H2 (g) Change the pressure: an increase in pressure will favor a shift toward the side with lowest number of gas particles. 3H2 (g) + N2 (g) 2NH3 (g) + heat C (s) + H2 (g) + heat CO (g) + H2 (g)

Change the temperature: increasing Temperature will drive the reaction toward the reactants (shift to left) if exothermic. increasing temperature will drive the reaction toward the products (shift to right) if endothermic. 3C + Fe2O3 3CO + 2Fe + 110.53kj 2H2O + 483.6kj 2H2(g) + O2(g)

“see-saw ride principle” Change in Concentration: adding more reactants always drives the reaction toward the products (shift to the right) adding more products always drives the reaction toward the reactants ( shift to the left) “see-saw ride principle” 3 H2 + N2 2NH3 CaCO3 CaO + CO2 Ca(OH)2 CaO + H20 Fe2O3 + 3CO 2Fe + 3CO2

Adding a Catalyst: does not cause a shift in equilibrium speed up or slow down only How do they show a catalyst?

H2(g) + Cl2(g) 2HCl(g) + 184kj Predict: forward, reverse, neither…… Addition of chlorine Remove HCl Increase pressure Decrease temperature Remove hydrogen Decrease pressure Add a catalyst Increase temperature Decrease system volume

PCl3(g) + Cl2(g) + 92.5kj PCl5(g) Predict: forward, reverse, neither….. Increase in temperature Decrease in pressure Decrease in volume Add more chlorine gas Add a catalyst Add phosphorus pentachloride Increase the pressure Decrease the temperature Add more phosphorus trichloride

The student will learn: 1. Using LeChatelier’s principles be able to predict production of the reaction based on the stress placed upon a reaction