Question

Give examples of exothermic reactions i.e. heat evolved in each of the following:

(a) reaction between a solid and a liquid
(b) reaction between two gases
Give two examples of exothermic reactions seen in everyday life.

Answer 1

(a) Reaction between a solid and a liquid:

CaO + H₂O → Ca(OH)₃ + Δ

(b) Reaction between two gases are:

\[\ce{N2 + 3H2 ⇌[Fe-450°][200 atoms.] 2NH3 + \triangle}\]
             [finely divided iron (Fe) - catalyst]

Examples of exothermic reactions are:

1. Rusting of iron – the reaction is slow and the heat evolved is very less, hence unnoticeable.
2. Setting of cement – cement setting liberates heat, hence concrete structures are set slowly.
3. Human Body – many chemical reactions in our body are exothermic & provide energy to survive.