What is water of crystallisation?

[jd12345]

Does the water molecule act as a ligand or is it trapped in the crystal lattice somehow?

If it is trapped in the crystal lattice then why it is found in a specific ratio? And why some metal salts like lithium form water of crystallisation more than other metal salts?

 

[Borek]

Does the water molecule act as a ligand or is it trapped in the crystal lattice somehow?

Both scenarios possible.

If it is trapped in the crystal lattice then why it is found in a specific ratio?

Crystal lattice contains well defined number of right sized vacancies that water molecule can fit in.

 

[jd12345]

Okay, i suppose the d-block elements mostly have water of crystallisaiton as ligands, right? And others like alkali metals in their crystal lattice?

Also what makes some salts like Lithium salts so deliquescent?