Question

Formation of nitric oxide is a highly exothermic reaction.
A. True
B. False

Answer 1

Exothermic reaction: It is the chemical reaction in which heat is released after the formation of a product takes place.
Endothermic reaction: It is the chemical reaction which absorbs heat energy to proceed the reaction and convert reactants into products.

Complete answer:
The molecular formula of nitric oxide is $NO$ and it is a colourless gas which is toxic in nature. It is widely used in medicines and is a major cause of pollution in the atmosphere and is responsible for acid rain.
The reaction involved in the formation of nitric oxide is as follows:
${N_2} + {O_2} \to 2NO$
In the reaction, the nitrogen gas reacts with oxygen gas to form two moles of nitric oxide. But in nitrogen gas, the nitrogen-nitrogen triple bond $(N \equiv N)$ is very strong. Similarly in oxygen gas, the oxygen-oxygen double bond$(O = O)$ is also very strong. Therefore, the reaction requires high energy to proceed.
Heat absorbed by the given reaction is $180kJ$. Hence the formation of nitric oxide is an endothermic reaction.

So, option (B) is the correct answer.

Note:
In endothermic reactions, the reactants are at lower energy levels as compared to products i.e., the products formed are less stable than the reactants. Therefore, the change in enthalpy of the reaction is positive for endothermic reactions.
In exothermic reactions, the reactants are at a higher energy level as compared to products i.e., the products formed are more stable than the reactants. Therefore, the change in enthalpy of the reaction is negative for exothermic reactions.