Question

How water molecules are held in the water of crystallization?

Answer 1

Reason for holding water molecules in the water of crystallization.

• The water of crystallization is referred to as the number of water molecules present in one formula unit of salt. For example: (${\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}$) Calcium sulfate dihydrate has 2 molecules of water of crystallization.
• These water molecules are held together with the compound by the special bonding called hydrogen bonding.
• Hydrogen bonding is one of the weak forces that result in the formation of dipole-dipole interaction.
• In Hydrogen bonding, the interaction is in between a hydrogen atom and an electronegative atom.
• The bonds formed by Hydrogen bonds are strong in comparison to normal dipole-dipole bonds.
• Crystalline salts mostly contain water in two different states of combination:
  Water of hydration
  Water of crystallization
• The water of crystallization is weakly bonded with the salt than the water of the hydration.
• It is easy to remove the water of crystallization than to remove the water of hydration.

Therefore, due to weak hydrogen bonds water molecules are held in the water of crystallization.