Question

$KN{O_3} + {H_2}O \to KOH + HN{O_3}$. The above reaction is _______ reaction

Answer 1

Chemical reactions which release energy after the reaction are called exothermic reactions. The chemical reactions which absorb energy for the reaction to take place are called endothermic reactions. All combustion reactions are considered as exothermic reactions.

Complete answer:
When an exothermic reaction takes place, the system loses heat and the surroundings gain heat. An endothermic reaction takes heat from the surroundings and makes the surroundings cold. There is an increase in the enthalpy and internal energy of the system during an endothermic process. In an exothermic reaction, the total energy of the products is less than the total energy of the reactants.
$KN{O_3} + {H_2}O \to KOH + HN{O_3}$
The above reaction is an endothermic reaction. Adding potassium nitrate to water is an example of an endothermic process. Because, when the crystal dissolves, the ions hydration does not provide as much energy that is needed to break up the lattice. The change in enthalpy will be positive if heat is provided for salt to dissolve which is endothermic and it is negative if heat is released for salt to dissolve in water which is an exothermic process.

Note:
To know whether the reaction is endothermic or exothermic, calculate the sum of enthalpies of products and those of reactants. If the sum of enthalpies of reactants is greater than that of products, then the reaction is said to exothermic. If the sum of enthalpies of products is greater than that of reactants, then the reaction is said to be endothermic.