# Equilibrium

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## The Equilibrium Constant

• Dynamic equilibrium: 1. The forward and backward reactions are going at the same rate 2. The amount of product and reactant remains the same
• Kc: This is a ratio worked out from the concentrations of the products and the reactants after equilibrium is reached. The value of Kc will only be true for that particular temperature.
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## La Chatelier's Principle

"If there's a change in concentration, pressure or temperature, the equilibrium will move to counteract the change."

• Temperature: Increasing the temperature, shifts the equilibrium in the endothermic (positive ΔH) direction to absorb the heat. Decreasing the temperature, shifts the equilibrium in the exohermic (negative ΔH) direction to replace the heat. If the change means more product is formed, Kc will rise, and if the change means more reactant is formed, Kc will decrease.
• Concentration: Increasing the concentration of the reactant, shifts the equilibrium to the right to counteract the change. Increasing the concentration of the reactan, shifts the equilibrium to the left in order to counteract that change. Concentration does NOT affect the value of Kc.
• Pressure/Volume: Increasing the volume of the container, causes the pressure to decrease, this results in equilibrium shifting to the side with the most moles in order to increase the pressure again. Decreasing the volume of the volume, causes the pressure to increase, which results in equilibrium shifting to the side with the least number of moles in order to decrease the pressure again. Pressure/volume does NOT affect the value of Kc.
• Catalyst: Catalysts have no affect on the position of equilibrium or on the value of Kc.This is because a catalyst increases the rate of both the forward and backward reactions by equal amounts.
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