Read the Assertion and Reason below and choose the correct option. — Chemical Equilibrium Chemistry Question

💡 Solution & Explanation

The formation of the blue tetrachloridocobaltate(II) complex from the pink hexaaquacobalt(II) complex is an endothermic process. According to Le Chatelier's principle, cooling the system (removing heat) shifts the equilibrium in the exothermic (backward) direction. The backward shift produces more Co(H₂O)₆²⁺, causing the solution to turn pink. Thus, the endothermic nature of the forward reaction perfectly explains the color change upon cooling. Therefore, correct answer is A.