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| Q: What is plaster of Paris? How is it prepared? | |||
| Ans:
Calcium sulphate hemi hydrated is commonly known as "plaster of
Paris". Chemical
formula: CaSO4.1/2H2O Plaster of Paris is prepared by gypsum. |
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Preparation
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| When gypsum is heated up to 1000C ,it loses some molecules of water of crystallization and forms an amorphous white solid known as plaster of Paris. | |||
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CaSO4.2H2O è
CaSO4.1/2H2O+ 3/2H2O
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Properties
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| Plaster of Paris when mixed with water sets within few minutes. The setting of plaster of Paris takes place with expansion and its surface becomes very smooth .Due to this property plaster of Paris is used in moulds. | |||
|
Question:
What is Epsom salt?
How is it prepared. |
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| Magnesium
sulphate hepta hydrated is commonly known as "Epsom salt". Chemical formula: MgSO4.7H2O |
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Properties
& uses
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| It
is a semi transparent white crystalline solid. It is soluble in water. It is used as purgative in medicines. It is used in Paper, soap and ceramics industry . |
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Methods
of preparation
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| Epsom
can be prepared by treating suitable substance with Sulphuric acid From Mg: |
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Mg + H2SO4
è MgSO4 + H2
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| From MgCO3 : | |||
| MgCO3 when treated with H2SO4. MgSO4 is obtained. | |||
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MgCO3 + H2SO4
è MgSO4 + H2O
+ CO2
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| From Mg(OH)2: | |||
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Mg(OH)2 + H2SO4
è MgSO4 + 2H2O
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| From MgO : | |||
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MgO + H2SO4
è MgSO4 + H2O
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Effect
of Heat
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| When Epsom is heated, it loses water of crystallization to form anhydrous magnesium sulphate. | |||
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MgSO4.7H2O
è MgSO4 + 7H2O
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