Picture (1)represents the equilibrium mixture for the reaction A + B ⇌ 2 AB at 298 K.
-If this reaction is endothermic,which picture (2)-(4)represents the equilibrium mixture at 400 K?

Question

Picture (1)represents the equilibrium mixture for the reaction A + B ⇌ 2 AB at 298 K. 
-If this reaction is endothermic,which picture (2)-(4)represents the equilibrium mixture at 400 K?

Quizplus · Accepted Answer

Since the reaction is endothermic, increasing the temperature will shift the equilibrium towards the product side in order to absorb the excess heat. Picture (2) shows an increased amount of AB, indicating the equilibrium has shifted towards the product side. Picture (4) shows a decreased amount of AB, indicating the equilibrium has shifted towards the reactant side. Picture (3) shows no change in the amounts of reactants and products, which is not possible when the temperature is increased for an endothermic reaction, therefore it is not the correct choice. However, picture (2) shows a relatively equal increase in the amounts of both A and AB, indicating that some of the reactants have reacted to form more products, which is a possible outcome for an endothermic reaction at an increased temperature. Therefore, B is the best choice.

Picture (1)represents the Equilibrium Mixture for the Reaction a