Question

Define exothermic reaction with an example.

Answer 1

Exothermic reaction - When a chemical change takes place by the release of heat energy, that change is called exothermic change.

Reactant $\to$Product + Energy

Example - Sodium (Na) reacts with water (H₂O) and forms Sodium hydroxide (NaOH) and liberates Hydrogen gas (H₂) with the release of energy.

$$\begin{gathered} \mathrm{Na}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)\to \mathrm{NaOH}\left(\mathrm{s}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)\uparrow \\ \mathrm{sodium}\mathrm{water}\mathrm{sodium}\mathrm{hydroxide}\mathrm{hydrogen} \end{gathered}$$