Question

When ammonium nitrate is dissolved in water contained in beakers, the water becomes cold.

Answer 1

Hint: As we know that the compounds formed have bonding strength, there are some forces which bind the atoms or molecules together. The polar molecules are bonded with ionic forces of attraction; these are very strong forces. When the lattice energy is greater than the hydration energy, compounds do not break into its ions and they need extra energy to break.

Step by step answer:
Ammonium nitrate is a polar molecule. It is a salt of ammonium hydroxide and nitric acid and they are bonded with strong force of attraction.
Due to the strong force of attraction, its lattice energy is high and it will not dissociate into water so it takes extra heat from water and hence the reaction is an endothermic reaction.
So, in this process all the heat from water is taken up by ammonium nitrate to break into its ions and water becomes cold.

Note: lattice energy is the energy of one mole of compound to break into its ions and the hydration energy is the energy released when ions are surrounded by water molecules and form bonding.
There are two cases as-
If lattice energy > hydration energy, the compound will not dissolve in water and the process will be endothermic. Endothermic process is represented by the positive value of energy.
If hydration energy > lattice energy, the compound will dissolve in water and the process will be exothermic. Exothermic process is represented by the negative value of energy.