what is water of crystallization? explain with the help of an example.
Answers
Answer:
Examples:
- CuSO4•5H2O - copper (II) sulphate pentahydrate
- CoI2•6H2O - cobalt (II) iodide hexahydrate
- SnCl2•2H2O - stannous (tin II) chloride dihydrate
Explanation:
Water of crystallization (alt. Br.E. water of crystallisation) is water that occurs in crystals but is not covalently bonded to a host molecule or ion. The term is archaic and predates modern structural inorganic chemistry, coming from an era when the relationships between stoichiometry and structure were poorly understood. Nonetheless, the concept is pervasive and when employed precisely, the term can be useful. Upon crystallization from water or moist solvents, many compounds incorporate water molecules in their crystalline frameworks. Often, in fact, the species of interest cannot be crystallized in the absence of water, even though no strong bonds to the "guest" water molecules may be apparent.
This species has the formula NiCl2(H2O)6. Examination of its molecular structure reveals that the crystal consists of [trans-NiCl2(H2O)4] subunits that are hydrogen bonded to each other and two isolated molecules of H2O. Thus 1/3 of the water molecules in the crystal are not directly bonded to Ni2+, and these might be termed "water of crystallization".