Why are some solution processes exothermic whereas others are endothermic?

Why some. reactions are exothermic while some others are endothermic?

State whether each of the following processes is exothermic or endothermic : KCl (s) + aq to KCl (aq) , DeltaH = + 18.6 kJ

An acid or abase is mixed with water is the process exothermic or endothermic one?

Classify the following processes as exothermic or endothermic. Melting of ice

Classify the following processes as exothermic or endothermic. Melting of ice

Dissolution of a solute is an exothermic process if: