Q.

Reactant A converts to product D through the given mechanism (with the net evolution of heat):

A→B  (slow)  ; ΔH=+ve

B→C  (fast)  ; ΔH=-ve

C→D  (fast)  ; ΔH=-ve

Which of the following represents the above reaction mechanism              [2025]

1  
2  
3  
4  

Ans.

(1)

As A→B is an endothermic reaction, EB>EA 

As B→C is an exothermic reaction, EC<EB 

As C→D is an exothermic reaction, ED<EC 

As net reaction is exothermic, ED<EA 

Only option (1) satisfies these conditions.