Question

Give an example of a combination reaction that is exothermic.

Answer 1

Combination reaction:

The reaction in which two or more reactants combine and form a product is called a combination reaction.

Exothermic reaction:

The reaction in which the overall standard enthalpy change $(∆\mathrm{H}°)$ is negative or heat is evolving is called an exothermic reaction.

Example of a combination reaction that is exothermic:

$\mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+\mathrm{Heat}$

In this reaction, calcium oxide (CaO) reacts with water to form calcium hydroxide$\left(\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\right)$ which clearly shows that it is a combination reaction. Also, the heat is released in this reaction which means the reaction is of exothermic nature.

Thus, the above chemical reaction is a combination reaction that is also an exothermic reaction.