What is hydrated salt?

hydrated salt it is a salt in which the ions of the compound incorporate water molecules into their crystalline lattices, which makes these molecules become part of the salt crystal.

Representation of the crystalline lattice of a salt

The chemical formula of a hydrated salt follows a pattern, in which we have the presence of any cation (X⁺), any anion (Y^-) and a certain amount (n) in moles of water, as can be seen in the following model:

XY.nH₂O

To form the nomenclature of a hydrated salt, we must carry out the following rules:

Anion name + de + cation name + prefix + hydrated

Note: The prefix indicated in the nomenclature rule refers to the amount in mol of water present in the salt formula, thus, for 1 mol (mono), 2 mol (d), 3 mol (tri), etc.

1st Example: FeCl₂.2.H₂O

This hydrated salt has the following components:

• Iron cation II (Fe⁺²);

• Chloride anion (Cl^-);

• 2 moles of H₂O (prefix di).

So its name will be iron II chloride dihydrate.

2nd Example: MgSO4₄.7.H₂O

This hydrated salt has the following components:

• Magnesium Cation (Mg⁺²);

• Sulfate anion (SO₄^-2);

• 7 mol of H₂O (prefix hepta).

So its name will be magnesium sulfate heptahydrate.

3rd Example: ZnBr₂.8.H₂O

This hydrated salt has the following components:

• Zinc cation (Zn⁺²);

• Bromide anion (Br^-1);

• 8 mol of H₂O (prefix octa).

So its name will be zinc bromide octahydrate.

chemical modification

When a hydrated salt undergoes a heating process, the water molecules incorporated into the crystalline structure are released in the form of vapor, leaving only a simple salt.

By Me. Diogo Lopes

Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/quimica/o-que-e-sal-hidratado.htm