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Chemical Equilibrium

• Equilibrium/ dynamic equilibrium the state achieved when the forward and reverse reactions occur simultaneously at the same rate and the concentration of the products and reactants stays constant.

• NB. Only occurs with a reversible reaction (⇌ )

• The concentration of the reactants and products does not need to be the sam

Le Chatelier’s Principle

• Le Chateliers principle if factors affecting equilibrium are changed, equilibrium tends to shift in the direction that will cancel out that change

• i.e a system will always do the opposite to the change that was done to it

The factors that cause a shift in equilibrium:

1. Pressure

• A change in pressure will cause a shift in equilibrium

• The greater the number of GAS molecules the greater the pressure as the molecules collide with the sides of the container.

• We can determine the number of gas molecules by looking at the big numbers in the reaction equation:

2C(s) + O2 (g)–> 2CO(g)

Changes in pressure:

• If the pressure increases, the system will try to decrease the pressure by shifting towards the side with the least gas molecules

• If the pressure decreases, the system will try to increase the pressure by shifting in the direction of the most gas molecules

• If the equilibrium shifts to the right, the concentration of the products will increase

and the concentration of the reactants will decrease.

• If the equilibrium shifts to the left, the concentration of the products will decrease

and the concentration of the reactants will increase. Yield is the amount of products formed

2. Change in temperature

• Enthalpy change values tell us whether the forward reaction is exothermic or endothermic

• If ΔH is -, forward reaction is exothermic and reverse reaction is endothermic

• ΔH is +, forward reaction is endothermic and reverse reaction is exothermic.

• Endothermic reactions get cooler

• Exothermic reactions get hotter

Shifts in equilibrium: If the temperature is increased, the system will try to decrease the temperature by favouring the endothermic reaction.

• If the temperature is decreased, the system will try to increase the pressure by favouring the exothermic reaction