Question

Which of the following will change the value of the equilibrium constant
Change in concentration of reactant
Change in the amount of catalyst
Change in pressure
Change in temperature

Answer 1

The equilibrium constant of a chemical reaction is defined as the value of its reaction quotient at chemical equilibrium. It is a condition which arises where the rates of forwarding and backward reaction are equal. This change occurs following Le-Chatlier’s principle which states that a system adjusts itself according to the change which happens in a system.

Complete step by step answer:
We know that the equilibrium constant doesn’t change on changing the concentration of the entities present at equilibrium. It is because on increasing the concentration of an entity the reaction proceeds in such a direction to neutralize that change following the Le-Chatelier's and keep the equilibrium constant the same. So the effect takes place on equilibrium constant and it remains the same.
A catalyst increases the rate of forwarding reaction and backward reaction to the same extent. Dynamic equilibrium is established when the rate of forwarding reaction and the rate of backward reaction becomes equal. When a catalyst speeds up both of the reactions to the same extent then they will remain equal without a change in equilibrium constant.
Changing pressure does not affect the equilibrium constant as we increase the pressure the reaction moves in such a direction to nullify that effect. It can be achieved by the reaction in that direction where fewer molecules are present. If there are the same number of molecules on both sides then there is no effect on the equilibrium constant.
Change in temperature affects the equilibrium for those reactions which are endothermic and exothermic. When the forward reaction is exothermic, increasing temperature decreases the value of the equilibrium constant and vice versa. So the equilibrium constant changes in changing the temperature.

Therefore the equilibrium constant is changed only by a change in temperature.

So, the correct answer is Option D .

Note: The equilibrium constant K is to be kept constant. To keep it constant, the imposed stress is neutralized by a change in the equilibrium position. If a system at equilibrium is subjected to change in pressure, temperature, and concentration the equilibrium is altered and the reaction takes place in some direction until the equilibrium is restored.