Which one of the following is the number of water molecules that share

Which one of the following is the number of water molecules that share with two formula unit CaSO₄ in plaster of Paris ?

[amp_mcq option1=”One” option2=”Two” option3=”Five” option4=”Ten” correct=”option1″]

This question was previously asked in

UPSC NDA-1 – 2018

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In plaster of Paris (CaSO₄ · ½ H₂O), one formula unit of CaSO₄ is associated with half a molecule of water. Therefore, two formula units of CaSO₄ share one molecule of water (2 * ½ H₂O = 1 H₂O).

Plaster of Paris is calcium sulfate hemihydrate (CaSO₄ · ½ H₂O). This chemical formula indicates the ratio of calcium sulfate to water molecules in the crystal structure.

When plaster of Paris is mixed with water, it rehydrates to form gypsum (CaSO₄ · 2H₂O), a hard solid. This process is exothermic and is the basis for its use in casting and construction.

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