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Question
State the methods by which hydrated salts can be made anhydrous.
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Solution
Hydrated salts can be converted to anhydrous substances by heating and also when exposed to dry air.
Example:
Glauber's salt becomes powdery anhydrous sodium sulphate when exposed to dry air.
\[\ce{Na2SO4.10H2O ->[dryair] NaSO4 + 10H2O}\]
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RELATED QUESTIONS
Give two examples of Crystalline anhydrous substances.
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A property due to which a substance absorbs water without dissolving.
Give the names and formulae of two substances
Anhydrous substance
Complete the following table:
|
Common Name |
Chemical Name |
Formula |
Acid, base or salt |
Efflorescent, hygroscopic or deliquescent substance |
|
Solid caustic potash |
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Quick lime |
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Oil of vitriol |
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Washing soda |
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Solid caustic soda |
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Blue vitriol |
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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.
Match the substances in List I with the appropriate answer in List II.
| List I | List II |
| 1. Green vitriol | A: Permanent hardness in water |
| 2. Paint | B: Hygroscopic |
| 3. Magnesium chloride | C: Temporary hardness in water |
| 4. Magnesium bicarbonate | D: Heptahydrate |
| 5. Calcium oxide | E: Colloidal |
Select the correct answer from the choice given in the options.
An anhydrous crystal _____.
Give a reason for the following:
Heating a hydrated copper sulphate crystal is deemed a chemical change.
Define Hydrated salt.
'A' is a blue coloured crystalline salt. On heating, it loses blue colour and to give 'B'. When water is added, 'B' gives back to 'A'. Identify A and B, write the equation.
