Question

In an exothermic reaction, the reactants:
(A) have less energy than the products formed.
(B) have more energy than the products formed.
(C) are at lower temperature than products.
(D) energy is released during reaction.

Answer 1

Think about the changes which take place when an exothermic reaction occurs. Try to break the word ‘exothermic’ and find its meaning. Take a look at all the options and then choose the best suitable option.

Complete step by step solution:
- All the bond-making processes are exothermic processes.
- In a bond-making process, atoms combine with each other and release energy.
- The word ‘exothermic’ can be split into two parts ‘exo’ and ‘thermic’.
- ‘Exo’ means to go out or vacate or evolve.
- ‘Thermic’ means related to thermal or heat energy.
- So, ‘exothermic’ is ‘heat-evolving’.
- An exothermic reaction is a process in which heat is released during the reaction.
- Crystallization is an example of an exothermic process.
- In crystallization, atoms or molecules orient themselves and arrange themselves in a repeated uniform manner to form crystals. This process leads to the evolution of energy.
- The question is asking about the state of reactants in exothermic reactions.
- Since in an exothermic reaction, energy is released, it indicates that reactants have high energy and are unstable and will form bonds to release energy and get stabilized. So, the products formed will comparatively have less energy than reactants.
- Therefore, in an exothermic reaction, the reactants have more energy than the products formed.

- Therefore, the answer is option (B).

Note: Remember exothermic reactions are bond-making processes and therefore, energy is released. For example, crystallization. The reactants will have more energy than the products. The species having more energy is highly reactive and will react simultaneously with evolution of energy in the form of heat and light.