What is the formula for Plaster of Paris?

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RPF SI Previous Paper 4 (Held On: 6 Jan 2019 Shift 1)
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  1. CH3COOH
  2. (NH4)2SO4
  3. CaSO4.1/2H2O
  4. CaSO4

Answer (Detailed Solution Below)

Option 3 : CaSO4.1/2H2O
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The correct answer is Option 3, i.e CaSO4.1/2 H2O

  • The chemical name of the Plaster of Paris is calcium sulphate hemihydrate.
  • The chemical formula of the Plaster of Paris is CaSO4.1/2 H2O.
  • Plaster of Paris is a quick-setting gypsum plaster which is composed of a fine white powder (calcium sulfate hemihydrate), that hardens when moistened and allowed to dry.
  • CH3COOH is Acetic Acid.
  • (NH4)2SO4 is Ammonium Sulfate.
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