When the temperature of an endothermic reaction at equilibrium is decreased

Question

When the temperature of an endothermic reaction at equilibrium is decreased ...

A)The equilibrium shifts to the LHS

b)The equilibrium shifts to the RHS

c)The equilibrium is not changed

d)None of these

Answer 1

An endothermic reaction is a reaction that absorbs heat from the environment and the heat is used to make the reaction happen. Therefore for an endothermic reaction, heat (temperature) will be on the reactant side. So by decreasing temperature you are essentially removing reactants. Le Chatlier's principle says that if you take away something from the reactants side, the reaction will shift to the side you are removing from so in this case the equilibrium will shift to the reactant side.

Example:

Heat + A + B ---> C + D

If you remove heat (reactant), the equilibrium shifts to A and B. Another way to think about it is because heat is required to turn reactants into products for an endothermic reaction, if you remove heat, less reactant will be able to turn into products so the equilibrium favors the reactants.