Question

When ammonium chloride is mixed with barium hydroxide in a beaker, it becomes cold.

Answer 1

When ammonium chloride is mixed with barium hydroxide in a beaker, the interaction occurs between the solute and solvent particles leading to the formation of bond and this makes the dissolution of ammonium chloride in barium hydroxide possible. This decreases the energy of the complete mixture.

Complete step by step solution:
-To be able to answer the above question, we must be familiar with all the types of reactions that occur in nature. There are various ways of classification of reactions. Based on the energy and stability, reactions can be classified as exothermic and endothermic. Based on the feasibility, reactions can be classified as feasible and infeasible reactions.
-Exothermic reactions are the reactions in which the energy is released into the system. In this type of reaction, the overall sum of the enthalpies of the reactants is greater than that of the product. As a result, the net change in enthalpy comes out to be negative in exothermic processes.
-Endothermic reactions are the reactions in which the energy is absorbed by the system. In this type of reaction, the overall sum of the enthalpies of the reactants is lesser than that of the product. As a result, the net change in enthalpy comes out to be positive in endothermic reactions.
-When a solute is added in a solvent, it leads to the breaking of the original solute-solute bond and also the solvent-solvent bond. A new type of bond is formed between the solute and the solvent to form the mixture. So, for any solution, we can say
Solute + solvent = solution.
-When a bond is broken, energy is required to do so. Here in our question, two different types of bonds are broken, 1 is in between the ammonium and the chloride ions and 1 is in between barium and hydroxide ions. The new bonds are formed between ammonium and hydroxide ions and also barium and chloride ions.
-It is theoretically observed that the energy needed to break the original bonds is much more than the energy which is released when the new bonds are formed. As a result, the overall reaction is an endothermic reaction. So, energy is absorbed by the system and this is why we feel the beaker to be cold.
Thus we can conclude that whenever ammonium chloride is mixed with barium hydroxide in a beaker, it becomes cold.

Note: Whenever an ionic reaction occurs so as to form a compound, energy absorbed is the ionization energy and energy released are the electron affinity as well as the lattice energy. Compounds are formed when the sum of lattice energy and electron affinity is more than the sum of all the ionization energies of the atoms.