Question

# Water of crystallisation in Green Vitriol is _____

Hint: Start the question by defining what water of crystallization is. Also, keep in mind that water of crystallization is a non-reactive part present in the compound.

water of crystallization is defined as, “water that is found in the crystalline framework of a metal complex or a salt, which is not directly bonded to the metal cation”.
Water molecules are often incorporated in the formation of crystals from aqueous solutions. These molecules do not react with the main component; it is just present inside crystals physically. It is saline and water soluble. It has an octahedral molecular geometry and is paramagnetic in nature.
Green vitriol is widely used in the manufacture of many iron salts, in water purification, fertilizer, as a colorant – in inks, tanning, pigments, photography, and in medicine - in the treatment of anaemia.
Green vitriol is an alternate term used for - crystalline Iron(II) sulphate or crystalline ferrous sulphate. Its chemical formula is - $FeS{{O}_{4}}.7{{H}_{2}}O$.
In the form of heptahydrate, ferrous sulphate occurs as blue-green crystals.
Therefore, we can conclude that water of crystallisation in Green vitriol is 7.

Additional information: A Crystal salt containing water of crystallization is known as a hydrate.

Note: Water of crystallisation is also known as water of hydration. It can be easily affected by heat. Some examples include-
• Copper(II) sulphate pentahydrate
• Cobalt(II) chloride hexahydrate
• Tin(II) (or stannous) chloride dihydrate