The reaction between Plaster of Paris (calcium sulfate hemihydrate) and water results in the formation of gypsum (calcium sulfate dihydrate). The chemical equation for this reaction is:
CaSO₄·(1/2)H₂O + 1.5H₂O → CaSO₄·2H₂O
Explanation:
CaSO₄·(1/2)H₂O: Represents Plaster of Paris, a calcium sulfate hemihydrate, which is a form of calcium sulfate that contains half a water molecule per unit.
1.5H₂O: Represents the water molecules needed to react with the Plaster of Paris.
CaSO₄·2H₂O: Represents Gypsum, a calcium sulfate dihydrate, which is a form of calcium sulfate that contains two water molecules per unit. This is the solid that forms when Plaster of Paris hardens.