Important compounds: CaO, CaCO3, CaSO4, cement, plaster of Paris
s-Block Elements · Chemistry
Study notes
Plaster of Paris sets into a hard cast. Explain the chemistry. Step 1: POP is CaSO₄·½H₂O (made by heating gypsum to 120°C). Step 2: Mix with water → rehydrates: CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O. Step 3: Gypsum crystals interlock as they reform → rigid mass. Step 4: Slight expansion on setting grips the mould — perfect for casts and statues!