Question

why dissolution of some solid compounds is exothermic while that of some other is endothermic?

Answer 1

some solid compound is endothermic because heat is used to break down interionic force of attraction between two or more than two element .
when we form new product by combining two or more than two compounds then the heat is released such as:
CaO+ H2O = Ca(OH)2+heat

Answer 2

$\huge{\rm{Answer :-}}$

● If solute-solvent interactions are stronger than solute-solute or solvent-solvent interactions, energy is released and the dissolution is exothermic. Hence, dissolution of such solid compounds are exothermic.

● If solute-solvent interactions are weaker than solute-solute or solvent-solvent interaction, energy is absorbed and the dissolution is endothermic. Again, dissolution of such solid compounds are endothermic.