Water of Crystallization
Question 1: Which of the following salts has no Water of Crystallization? Blue vitriol, Baking soda, Washing soda, and Gypsum.
Answer:
Out of the four given salts, only baking soda does not contain water of crystallization as its chemical formula is NaHCO3.
Question 2: Name a salt which does not contain Water of Crystallization.
Answer:
There is a huge number of salts that does not contain water of crystallization, that are Sodium Nitrate (NaNO3), Potassium Chloride (KCl), Potassium Nitrate (KNO3), etc.
Question 3: Give any three compounds comprising water of crystallization.
Answer:
Here is the list of Salts that comprising of water of crystallization:
- Copper (II) Sulfate Pentahydrate (CuSO4.5H2O),
- Cobalt (II) Chloride Hexahydrate (CoCl2.6H2O),
- Tin (II) (or Stannous) Chloride Dihydrate (SnCl2.2H2O), etc.
Question 4: Why do salts containing water of crystallization appear to be perfectly dry?
Answer:
The water of crystallization is a part of the crystal structure of water. Since the water of crystallization is not free water, so it does not wet the salt. Thus, the salts containing water of crystallization appear to be perfectly dry.
Question 5: How is the water of crystallization useful for the crystals of salts?
Answer:
The water of crystallization gives the crystals of salts their shape and in some cases imparts their colour. For example, the presence of the water of crystallization in iron sulphate crystals imparts them a green colour.
Question 6: Write the name and formula of a salt that has five molecules of crystallisation water in it.
Answer:
Copper sulphate crystals include five molecules of water of crystallisation in one formula unit. Its formula is CuSO4.5H2O.
Question 7: What is the colour of FeSO4.7H2O crystals? What happens to the colour when it’s heated?
Answer:
FeSO4.7H2O crystals are green in colour. It loses the water of crystallisation when heated, resulting in anhydrous ferrous sulphate. It has a reddish-brown colour to it.
Question 8: Is water present in anhydrous sodium chloride crystals?
Answer:
Since there are no water molecules in an anhydrous material, so there is no water present in anhydrous sodium chloride crystals. These anhydrous crystals were created by carefully eliminating the water of crystallisation from hydrated salts.
Question 9: Why do copper sulphate crystals change colour when heated?
Answer:
The blue colour of the copper sulphate crystals turns white on heating because of the loss of water during crystallisation.
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.