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Question
Differentiate between ‘hydrated’ & ‘anhydrous’ crystals. Give the chemical formula of – the following hydrated crystals -
(a) Washing soda
(b) Gypsum
(c) Blue vitriol
(d) Epsom salt
(e) Glauber’s salt.
State which crystal from (a) to (e) is a pentahydrate.
Solution
| Hydrated crystals | Anhydrous crystals |
| Hydrated crystals contain a definite number of water molecules (as water of crystallisation) in a loose chemical combination with the crystal. | Anhydrous crystals do not contain any definite number of water molecules in loose chemical combinations with the crystal. |
| E.g., CuSO4.5H2O | E.g., KNO3 |
The formula of hydrated crystals:
(a) Washing soda: Na2CO3.H2O
(b) Gypsum: CaSO4.2H2O
(c) Blue vitriol: CuSO4.5H2O
(d) Epsom salt: MgSO4.7H2O
(e) Glauber’s salt: Na2SO4.10H2O
Blue vitriol [CuSO4.5H2O] is a pentahydrate.
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