Question

What are called exothermic and endothermic reactions?

Answer 1

In an exothermic reaction, the potential energy or inherent energy of the system decreases as the reactants are transformed into products.

This reaction  releases energy in the for of heat.  Ex- Combustion.

Chemical reaction which proceeds via absorption of heat energy is called endothermic reaction.

This reaction absorbs energy in the form of heat. Ex- Electrolysis.

Answer 2

1) Exothermic reactions - Those reactions in which heat is evolved .

♥ Examples :-

(i) C (s) + O2 (g) → CO2 (g) + Heat

(ii) N2 (g) + 3H2 (g) → 2NH3 (g) + Heat

2) Endothermic reactions - Those reactions in which heat is absorbed .

♥ Examples :-

(i) C (s) + 2S (s) → CS2 (l) – Heat

(ii) N2 (g) + O2 (g) → 2NO(g) – Heat