tis it true that no activation energy is needed at all for exothermic reaction since energy is liberated. It is been told to us as false if so there are many reaction in chemistry saying energy evolved in 1 st reaction is used to carry out 2nd​ reaction getting confused plzzz help

Dear Student,

Activation energy is defined as the minimum amount of energy which reactants must possess to undergo a reaction and form products.
For any reactants to interact, they need to have sufficient kinetic energy which will lead to an increase in the number of collisions between the reactant species and thus reactions between the species to form products. The bonds present in the reactants also need to be broken to form new bonds with other reactants and energy is also required for breaking the bonds.
Thus, the minimum energy required for breaking the chemical bonds and increasing the number of collisions between the reactant species can be called as the activation energy.

Even exothermic reactions require the step of bond breaking and excitation of the species leading to collisions. In multistep exothermic reactions, bond formation between the different reactants in the first step leads to formation of energy and this energy is used up to provide the activation energy for a subsequent step.

Image result for activation energy for exothermic reaction

Hope it helps. 


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For breaking of bond of the molecules , firstly energy is required.As the reaction proceeds free radicals are formed and they are very reactive ,so less or no energy is required for further reaction and energy is released on reaction(formation of products) for more new reactions to occur.
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