A D is an endothermic reaction occurring in three steps (elementary). (i) A B H _ i =+ ve (ii) B C H _ i i =- ve (iii) C D H _ i i i =- ve Which of the following graphs between potential energy ( y -axis) vs reaction coordinate (x -axis) correctly represents the reaction profile of A D ?

Step-by-step solution

The reaction A → D occurs through three elementary steps with energy changes: Step (i): A → B is endothermic ( H_I = +ve ), so B has higher energy than A, creating the first peak. Step (ii): B → C is exothermic ( H_ II = -ve ), so C has lower energy than B, creating a lower second peak. Step (iii): C → D is exothermic ( H_ III = -ve ), so D has lower energy than C, creating an even lower third feature. Overall reaction: Since step (i) is endothermic and steps (ii) and (iii) are exothermic, the reaction can be endot