Answer : The correct option is, (2) Fission reaction.
Explanation :
- Fission reaction : This is a type of nuclear reaction in which the splitting of bigger nuclei into two smaller nuclei takes place. During this process, the large amount of energy is released.
- Redox reaction : This is an oxidation-reduction reaction in which the electrons transferred between the two molecules.
- Substitution reaction : In this reaction, one functional group is replaced by the another functional group in a chemical compound.
- Neutralization reaction : In this reaction, the acid and base react to give water and a salt.
Redox reaction, substitution reaction and neutralization reaction are the chemical reactions in which the heat releases when the chemical bonds are breaking and forming.
Therefore, the greatest amount of energy released per gram of reactants occurs during the fission reaction.