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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.
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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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RELATED QUESTIONS
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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What are hydrous substances? Explain with examples.
Explain the following observation:
In the expression anhydrous copper sulphate, what is meant by “anhydrous”?
Select the correct word from the words in option to complete the sentence:
Efflorescence occurs when the vapour pressure of the hydrated crystals is ____ than the vapour pressure of the atmospheric humidity.
Select the correct answer from the choice given in the options.
An anhydrate of a heptahydrate salt _____.
The molecular formula of green vitriol is MgSO4.7H2O.
Define Hydrated salt.
A hot saturated solution of copper sulphate forms crystals as it cools. Why?
'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.
What happens when MgSO4.7H2O is heated? Write the appropriate equation?
