Question

Which of the following is an endothermic process?
A.Reaction of water with quick lime
B Dilution of an acid
C.Neutralization of an acid using base
D.Sublimation of camphor crystals

Answer 1

Endothermic reaction is the reaction in which the amount of energy is absorbed during a chemical reaction and exothermic reaction is the reaction in which the amount of energy is released during a chemical reaction. So we will check whether each reaction is endothermic or not.

Complete step-by-step answer: Calcium oxide $\left( {CaO} \right)$ is also known as quicklime. When quick lime is treated with water, calcium hydroxide is produced. The reaction is given as-
${\text{CaO + }}{{\text{H}}_2}{\text{O}} \to {\text{Ca}}{\left( {{\text{OH}}} \right)_2}$
In this reaction, heat is evolved during the reaction. Hence this reaction is an exothermic reaction.
Dilution of acid is done by adding concentrated acid to water which reduces the concentration of ${{\text{H}}^ + }$ ions in the solution. This changes the pH of the acid. This reaction is also exothermic as heat is evolved in this reaction.
Neutralization of an acid is a process in which a base is added to a base to form salt and water. This process neutralizes the acid. The reaction is given as-
${\text{NaOH + HCl}} \to {\text{NaCl + }}{{\text{H}}_2}{\text{O}}$
This is the most common example in which the product is a common salt. This type of reaction is also an exothermic reaction.
Sublimation of camphor crystals is an endothermic process as heat is absorbed by the crystal due to which the solid crystals change phase from solid to gas without passing the liquid stage. It occurs at temperature and pressure below the crystals triple point.

The correct answer is option ‘D’.

Note: Here we should remember that when water is added to the acid, too much heat is released and the solution can boil vigorously and get splashed out of the container. So if you want to dilute acid, add acid to the water and not water to acid.