Plaster- Paris

Plaster – Paris 

source : indian express.com

Plaster of Paris  [ (Ca SO4)2 . H2O]

or

Calcium sulphate hemihydrate CaSo4 . 1/2 H2O

Methods  of preparation:

From Gypsum — When gypsum is heated at 120 degree C to 130 degree C , plaster of paris is obtained.

2(CaSo4 . 2H2O) ——-> (CaSo4)2 . H2o + 3H2O

Properties:

1. It is white  powder, sparingly soluble in water.
2. Effect of heat: At 200 degree C anhydrous calcium sulphate is obtained. At 1200 degree C  it decomposes.

[(CaSo4)2.H2O] ——–> 2 CaSo4 + H2O

2[ CaSo4] ——-> 2 Cao + 2So2 + O2

3. Reaction with water: Gypsum is obtained which sets as hard mass. This process is called setting of plaster of paris.

(CaSo4)2 . H2O +3H2O ——-> 2[CaSo4.2H2O]

Uses:

a) for setting dislocated or broken bones.

b) In making chalks.

c) For making toys and statues.

Conversions:

•  (Barium sulphate to barium chloride:

BaSO4 +4C(coke) ——–>BaS(barium sulphide) + 4CO( carbon monoxide)

BaS + 2HCl ——–> BaCl2 + H2S

• Calcium sulphate to Calcium chloride:

CaSO4 + 4C ——–> CaS + 4CO

CaS + 2HCl ——–> CaCl2 + H2S

• Barium sulphate to Barium nitrate:

BaSO4 + 4C ——–> BaS + 4CO

BaS + 2 HNO3 ———> Ba (NO3)2 + H2S

• Hydrated magnesium chloride to magnesium oxide:

MgCl2 . 6H2O——-> Mg( OH)Cl + HCl + 5H2O

Mg(OH)Cl ———> Mgo + HCl

• Hydrated magnesium chloride to anhydrous magnesium chloride:

MgCl2 . 6H2O ——–> Mg(OH)Cl + HCl + 5H2O

Mg(OH)Cl + HCl(dry gas) ——–> MgCl2 + H2O

• Barium nitrate to Barium chloride:

Ba(NO3)2 ——–> BaO + NO2 + O2

BaO + 2HCl ——–> BaCl2 + H2O

• Barium nitrate to Barium sulphate

Ba (NO3)2 ———> BaO + NO2 + O2

BaO+ H2SO4 ———> BaSO4 + H2O

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