Question

Separate out exothermic and endothermic process from the following:

${\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\to 2{\mathrm{NH}}_3+92\mathrm{kJ}$

Answer 1

Energy changes during a reaction

A chemical reaction involves either evolution or absorption of energy.

• The reactions which involve the formation of a higher energy product from a lower energy reactant require energy. Therefore, energy is absorbed during the reaction, and these reactions are called endothermic reactions.
• The reactions that involve the formation of a lower energy product from a higher energy reactant cause an increase in the system's energy, which is released in the form of heat. These reactions are called exothermic reactions.

The reaction between nitrogen gas and hydrogen gas

In the given reaction, nitrogen $\left({\mathrm{N}}_2\right)$ gas and hydrogen $\left({\mathrm{H}}_2\right)$ gas react to form ammonia $\left({\mathrm{NH}}_3\right)$ gas and heat. The balanced chemical equation is given as:

${\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\to 2{\mathrm{NH}}_3\left(\mathrm{g}\right)+92\mathrm{kJ}$

Here, heat is also evolved with a value of 92 kJ along with the product and is released to the surruounding. Thus, the reaction is an example of an exothermic process.