Action of Heat on Hydrated Salts
When hydrated salts are heated to high temperatures, they lose their crystallisation water. The hydrated salts lose their regular shape and colour when the water of crystallisation is lost, and they become colourless powdery particles. Since there is no water of crystallisation in anhydrous salts, so when water is added to an anhydrous salt, it hydrates and returns to its original colour. The following example will help to clarify this.
The copper sulphate crystals are blue in colour. When copper sulphate crystals are heated to a high temperature, they lose all of their water and become anhydrous copper sulphate, which is white.
CuSO4.5H2O → CuSO4 + 5H2O
(Hydrated copper sulphate) (Anhydrous copper sulphate) (Water)
As a result of the loss of water during crystallisation, blue copper sulphate crystals turn white when heated vigorously. Copper sulphate crystal dehydration is a reversible process. As a result, adding water to anhydrous copper sulphate causes it to become hydrated and turn blue, resulting in the production of hydrated copper sulphate.
CuSO4 + 5H2O → CuSO4.5H2O
(Anhydrous copper sulphate) (Water) (Hydrated copper sulphate)
When you add water to anhydrous copper sulphate, it turns blue. This property of anhydrous copper sulphate is utilised to detect the presence of moisture or water in a liquid. To white anhydrous copper sulphate powder, a few drops of the liquid to be tested are added. The presence of moisture or water in anhydrous copper sulphate is indicated by the appearance of blue colour.
Water of Crystallization
Crystallization is a technique for separating solids from a solution or, to put it another way, a procedure for purifying things. This is the most frequent method for purifying seawater. Some salts have a few water molecules in their crystal structure as an essential component. The water of crystallisation refers to the water molecules that make up a crystal’s structure. Hydrated salts are salts that contain the water that causes crystallization. Below is a detailed explanation of crystallisation of water, hydrated and anhydrous salts, and also the action of heat on the hydrated salts.