7.2.3 Apply Le Chatelier's principle to predict the effect on the value of Kc if pressure or volume or concentration is changed

Le Chatelier's Principle
At equilibrium the Kc of the reaction will remain constant. So if the product is remove, the reactant will react to qiuckly replace those product to keep the Kc constant, we say the eqiulibrium shift to the right to favor more prodcut. Similarly, if we add more reactant, they will qiuckly react to produce more product to keep the Kc constant, eqiulibrium shift to the right. From this this we conclude that, if the system, at eqiulibrium, experienced a change, the eqiulibrium will shift to minimize the effect of those change.

Change in conditions	Nature of the reaction at equilibrium	Effect on Kc	Effect on equilibrium to keep the Kc constant	Notes
Increase concentration of reactants	Constant concentration of  reactant/product	Decrease	Shift to the right to favour the product	You are putting in more reactants and decreasing the Kc so the system balances this out by shifting the equilibrium to the right to produce more products.
Removing the products after they have been formed	Constant concentration of  reactant/product	Decrease	Shift to the right to favour the product	You are putting in more reactants and decreasing the Kc so the system balances this out by shifting the equilibrium to the right to produce more products.
Increasing the pressure of a gaseous reaction	Increase in volume/pressure, when reactants react into product.	Increases	Shift to the left to favour the reactant	You are changing the condition to favour the nature of the reaction at equilibrium so more product is produce and Kc increase. The system then balances this out by shifting the equilibrium to the left to get more reactants.
Decreasing the pressure of a gaseous reaction	Decrease in volume/pressure, when reactants react into product.	Increases	Shift to the left to favour the reactant	You are changing the condition to favour the nature of the reaction at equilibrium so more product is produce and Kc increase. The system then balances this out by shifting the equilibrium to the left to get more reactants.
Decreasing the temperature of an endothermic reaction	Endothermic when reactants react into product.	Increase	Shift to the left to favour the reactant	You are changing the condition to favour the nature of the reaction at equilibrium so more product is produce and Kc increase. The system then balances this out by shifting the equilibrium to the left to get more reactants.
Increasing the temperature of an exothermic reaction	Exothermic when reactants react into product	Increase	Shift to the left to favour the reactant	You are changing the condition to favour the nature of the reaction at equilibrium so more product is produce and Kc increase. The system then balances this out by shifting the equilibrium to the left to get more reactants.
Decreasing the pressure of a gaseous reaction	Increase in volume/pressure, when reactants react into product.	Decrease	Shift to the right to favour the product	You are changing the condition to go against the nature of the reaction at equilibrium so fewer products is produce and Kc decrease. The system then balances this out by shifting the equilibrium to the right to produce more products. This one is use in Haber process.
Increasing the pressure of a gaseous reaction	Decrease in volume/pressure, when reactants react into product.	Decrease	Shift to the right to favour the product	You are changing the condition to go against the nature of the reaction at equilibrium so fewer products is produce and Kc decrease. The system then balances this out by shifting the equilibrium to the right to produce more products. This one is use in Contact process.
Decreasing the temperature of an exothermic reaction	Exothermic when reactants react into product	Decrease	Shift to the right to favour the product	You are changing the condition to go against the nature of the reaction at equilibrium so fewer products is produce and Kc decrease. The system then balances this out by shifting the equilibrium to the right to produce more products. This one is use in Contact/Haber process.
Adding a catalyst	Doesn’t matter	No effect	No effect	Adding catalyst will increase the rate of reaction but make no effect to the equilibrium. However, both Contact/Haber process use catalyst since they lower the pressure so the collision frequency, KE of particle(less than Ea) and rate of reaction decrease. So they use catalyst to compensate.

Note- If Kc increase the equilibrium will shift to the left to balance it out. If Kc decrease then the equilibrium will shift to the right to balacne it out.