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Question
Differentiate between hydrated and anhydrous crystals with examples. State three defined changes that occur when hydrated copper sulphate is heated.
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Solution
Difference between hydrated and anhydrous crystals:
| Hydrated crystal | Anhydrous crystal |
| (i) Contains fixed number of water molecules. | (i) Does not contains any fixed number of water molecules |
| (ii) CuSO4, 5H2O, FeSO4.7H2O are examples. | KNO3, K2SO4 are examples. |
Three defined changes: When CuSO4. 5H2O is heated take place are: (blue).
- Colour changes from blue to colourless.
- Changed to AMORPHOUS white powder
- Geometric shape vanishes
- On cooling and adding water colour restores but crystalline does not shape.
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State the methods by which hydrated salts can be made anhydrous.
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.
Explain the following observation:
In the expression anhydrous copper sulphate, what is meant by “anhydrous”?
Differentiate between the following:
Deliquescent salt and hygroscopic salt
Match the following
| 1. | Blue vitriol | CaSO4.2H2O |
| 2. | Gypsum | CaO |
| 3. | Deliquescence | CuSO4.5H2O |
| 4. | Hygroscopic | NaOH |
