Find the correct chemical formula for gypsum. Learn about calcium sulfate dihydrate, hemihydrate (Plaster of Paris), and anhydrite with formulas and uses. The correct answer is CaSO4.1/2 H2O. EXPLANATION: Plaster of Paris (POP) is a quick-setting gypsum plaster consisting of a fine white powder (calcium sulfate hemihydrate), which hardens when moistened and allowed to dry. It is also known as the Plaster of Paris because for the preparation of POP, the abundant gypsum was first found near the capital city of France i.e. Paris. The chemical formula of the Plaster of Paris is CaSO4. 1 2 H2O. Therefore option 3 is correct. Application of Plaster ... 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. Discover the chemical formula for Gypsum, Calcium Sulfate Dihydrate (CaSO4.2H2O). Learn its composition and distinguish it from Plaster of Paris and Anhydrite.