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Hydrated and Anhydrous Salts (Test for Water)
- Hydrated salts are salts that contain water of crystallization, which affects their molecular shape
and color.
- Water of crystallization is the water that is stoichiometrically included in the structure of some
salts during the crystallization process.
- Water of crystallization is indicated with a dot written between the salt molecule and the
surrounding water molecules.
- Anhydrous salts are those that have lost their water of crystallization, usually by heating.
- In our syllabus, there are two examples of hydrated salts that we must know about:
(i) Hydrated and Anhydrous Copper(II) Sulfate
- Water can be added to anhydrous copper(II) sulfate to form hydrated copper(II) sulfate. This is a
reversible reaction:
Copper(II) sulfate (CuSO₄) + 5 water (H₂O) ⇌ hydrated copper(II) sulfate (CuSO₄·5H₂O)
- Anhydrous copper(II) sulfate is a white powder, while hydrated copper(II) sulfate is a blue
crystal.
- In this case, the forward reaction is exothermic, and the backward reaction is endothermic.
(ii) Hydrated and Anhydrous Cobalt(II) Chloride
- Water can be added to anhydrous cobalt(II) chloride to form hydrated cobalt(II) chloride. This is
a reversible reaction:
Cobalt(II) chloride (CoCl₂) + 6 water (H₂O) ⇌ hydrated cobalt(II) chloride (CoCl₂·6H₂O)
- Anhydrous cobalt(II) chloride is a blue powder, while hydrated cobalt(II) chloride is a pink
crystal.
- In this case, the forward reaction is exothermic, and the backward reaction is endothermic.
The Haber Process
- The Haber Process is the manufacturing of ammonia at an industrial scale. There are certain
conditions regarding the Haber Process that you must know:
Nitrogen gas (N₂) + 3 hydrogen gas (H₂) ⇌ 2 ammonia (NH₃)
- In this reaction:
- The temperature is 450°C
- The pressure is 200 atm / 20,000 kPa
- The catalyst used is iron (Fe)