Equilibrium and LeChatelier's Principle

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Equilibrium and LeChatelier’s Principle : 

Equilibrium and LeChatelier’s Principle

Reversible Reactions : 

Reversible Reactions Some reactions are reversible, meaning the reactants form products, but the products can react with each other to form the reactants again.

Reversible Reaction Example : 

Reversible Reaction Example Hydrogen reacts with fluorine to make hydrogen fluoride. H2 + F2  2HF As the hydrogen fluoride is made, it starts to react with each other to make hydrogen and fluoride. H2 + F2  2HF

Equilibrium Systems : 

Equilibrium Systems Two reactions taking place at the same time. At first, the forward reaction is faster than the reverse reaction Eventually, the rate of the forward reaction equals the rate of the reverse reaction Both reactions still occur, but at the same rate in both directions

Examples of Equilibrium : 

Examples of Equilibrium

Examples of Equilibrium : 

Examples of Equilibrium

Examples of Equilibrium : 

Examples of Equilibrium

At Equilibrium… : 

At Equilibrium… Most often, the amounts of products and reactants are not equal Knowing the concentration of each product and each reactant helps describe the equilibrium through the use of an equilibrium constant

At Equilibrium… : 

At Equilibrium… The reaction is still going on. However the rate of the forward reaction is the same as the rate of the reverse reaction. There is no net change. This is an example of dynamic equilibrium.

LeChâtelier's Principle : 

LeChâtelier's Principle If a stress is applied to a system at equilibrium, the equilibrium shifts to relieve the stress.

What is a stress? : 

What is a stress? Chemical reaction Change in concentration of a reactant or product Change in temperature Change in pressure if a gas is involved

Change in concentration of a reactant or product : 

Change in concentration of a reactant or product Adding either reactant or product Removing either reactant or product Dilute the whole reaction vessel

Change in temperature : 

Change in temperature Heat it Cool it

Change in pressure if a gas is involved : 

Change in pressure if a gas is involved Increase volume Decrease volume Increase temperature Decrease temperature Add another gas Not involved in reaction

Direction of Shift : 

Direction of Shift Away from addition Toward something taken Increased pressure – move to side with fewer gases Decreased pressure – move to side with more gases

PCl5(g) + energy  PCl3(g) + Cl2(g) : 

PCl5(g) + energy  PCl3(g) + Cl2(g) Increase in Cl2 concentration Shifts Left Reactants Products

PCl5(g) + energy  PCl3(g) + Cl2(g) : 

PCl5(g) + energy  PCl3(g) + Cl2(g) Decrease in PCl5 concentration Shifts Left Reactants Products

PCl5(g) + energy  PCl3(g) + Cl2(g) : 

PCl5(g) + energy  PCl3(g) + Cl2(g) Increase in temperature Shifts Right Reactants Products

PCl5(g) + energy  PCl3(g) + Cl2(g) : 

PCl5(g) + energy  PCl3(g) + Cl2(g) Decrease in pressure 1 mole gas  2 moles gas Shifts Right