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  3. Chemistry
  4. For an exothermic reaction, following two steps are involved. Step 1. A + B arrow I (slow) Step 2. I arrow AB (fast) Which of the following graphs correctly represent this reaction ?

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Q. For an exothermic reaction, following two steps are involved.
Step 1. $A + B \rightarrow I$ (slow)
Step 2. $I \rightarrow AB$ (fast)
Which of the following graphs correctly represent this reaction ?

NTA AbhyasNTA Abhyas 2022

Solution:

In any reaction mechanism the no. of activated complexes showing maxima of potential energies is the no. of steps in that mechanism and in between these maxima is a valley where lies a more stable intermediate. There is one reaction intermediate lying at valley of two maxima representing two steps. Ea for first step should be higher than second step as first is slow step. These requirements fulfilled by choice (ii) & not choice (i) the choice (iv) is not possible because that is for endothermic reaction $\left(\Delta \text{H} + \text{ve}\right)$ & (ii) is single step equation so not possible.