Question

Give one word for the following:

Chemical reactions in which heat is evolved

Answer 1

Exothermic reaction:

• A chemical reaction that proceeds with the evolution of heat energy is called an exothermic reaction.
• Heat is evolved when new bonds are formed
• In general an exothermic reaction can be represented as
• $\mathrm{A}+\mathrm{B}\stackrel{}{\to }\mathrm{C}+\mathrm{D}+\mathrm{Q}\mathrm{kcal}(\mathrm{heat}\mathrm{evolved})$
• For example when carbon($\mathrm{C}$) reacts with oxygen, it forms carbon dioxide(${\mathrm{CO}}_2$), and heat is evolved.
• $$\begin{gathered} \underset{\mathrm{carbon}}{\mathrm{C}\left(\mathrm{s}\right)}+\underset{\mathrm{oxygen}\mathrm{gas}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\stackrel{}{\to }\underset{\mathrm{carbon}\mathrm{dioxide}\mathrm{gas}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}+94.5\mathrm{kcal} \\ \mathrm{or} \\ \underset{\mathrm{carbon}}{\mathrm{C}\left(\mathrm{s}\right)}+\underset{\mathrm{oxygen}\mathrm{gas}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\stackrel{}{\to }\underset{\mathrm{carbon}\mathrm{dioxide}\mathrm{gas}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}+\mathrm{heat}\mathrm{energy} \end{gathered}$$