Question

Explain why all decompositions are endothermic reactions.

Answer 1

Endothermic reaction:

1. As the name indicates ‘endo’ means ‘inside’ and ‘thermic’ means ‘heat’, i.e. heat is given to substance.
2. Endothermic reactions are those processes in which heat is given to the compounds for the reaction to occur.
3. Examples of an endothermic reaction, boiling of water, melting of ice, evaporation of iodine vapours, etc.

${\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

Decomposition:

1. Decomposition reaction involves the formation of two or more compounds from a single compound.
2. In a decomposition reaction, one compound breaks to form two or more compounds.
3. It involves the breaking of bonds.
4. To break the bonding between atoms, energy is required.
5. By providing energy in the form of heat or electricity, decomposition proceeds.
6. As this reaction involves the breaking of the bond, energy is provided to them, so they are endothermic reactions.
7. Examples of decomposition reactions are the decomposition of Nitrogen oxide into Nitrogen gas and Oxygen gas.

$\underset{\mathrm{Nitogen}\mathrm{oxide}}{2\mathrm{NO}\left(\mathrm{g}\right)}\stackrel{Heat}{\to }\underset{Nitrogen}{{\mathrm{N}}_2\left(g\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}$

Hence, all decompositions are endothermic reactions.