Question

Which among the following changes are exothermic or endothermic in nature.

Dissolution of ammonium chloride in water.

Answer 1

• Endothermic reactions are reactions where energy is absorbed in the form of heat. For example, the melting of ice cubes.
• Exothermic reactions are reactions in which energy is released in the form of heat. For example, Rusting of iron.

Dissolution of ammonium chloride in water:

When ammonium chloride is dissolved in water it dissociates into its corresponding ions i.e. ${{\mathrm{NH}}_4}^{+}$(ammonium ion) and ${\mathrm{OH}}^{-}$(hydroxide ion). The following reaction takes place:
$\text{N}{\text{H}}_{\text{4}}\text{Cl}\rightleftharpoons {\text{NH}}_4^{+}+\text{C}{\text{l}}^{-}$

In this reaction, the heat is absorbed from the surroundings and the temperature of the system decreases thus it is an endothermic reaction.