The chemical formula of gypsum is ______.

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SSC CGL 2022 Tier-I Official Paper (Held On : 07 Dec 2022 Shift 2)
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  1. CaSO4.12H2O
  2. MgSO4.12H2O
  3. MgSO4.2H2O
  4. CaSO4.2H2O

Answer (Detailed Solution Below)

Option 4 : CaSO4.2H2O
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The correct answer is CaSO4.2H2O.

Key Points

  • The chemical formula of gypsum is CaSO4.2H2O.
  • A soft sulphate mineral called gypsum is made up of calcium sulphate dihydrate.
  • It is widely mined, used as fertiliser, and the primary component of numerous plaster, sidewalk or blackboard chalk, and plasterboard products. 
  • Several cultures, including Ancient Egypt, Mesopotamia, Rome, the Byzantine Empire, and the Nottingham alabasters of Medieval England, have employed alabaster, a fine-grained, white or subtly coloured type of gypsum, for sculpture.
  • Gypsum can also form selenite crystals, which are transparent. 

Additional Information

  • Gypsum
    • The Greek word "o" (gypsos), which means "plaster," is where the name "gypsum" comes from.
    • Gypsum which has been dehydrated and used for various purposes for a long time has acquired the name plaster of Paris thanks to the quarries in the Parisian neighbourhood of Montmartre.
    • Plaster of Paris hardens or "sets" in ways that are beneficial for casting and construction after adding water and after a few dozen minutes returns to being ordinary gypsum (dihydrate).

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