Calcination of CaSO42H2O at 130° leads to formation of
## **Core Concept**
Calcination is a process in chemistry that involves the thermal treatment of a substance to bring about decomposition or phase transition. In the context of calcium sulfate (CaSO4·2H2O), calcination leads to the removal of water molecules, resulting in the formation of different calcium sulfate phases.
## **Why the Correct Answer is Right**
When CaSO4·2H2O (gypsum) is heated at 130°C, it undergoes partial dehydration. This process leads to the formation of **CaSO4·½H2O (Plaster of Paris)**. The reaction can be represented as: CaSO4·2H2O → CaSO4·½H2O + 1½H2O. This product, Plaster of Paris, is known for its use in making molds and casts.
## **Why Each Wrong Option is Incorrect**
- **Option A:** CaSO4 (Anhydrite) is formed when calcium sulfate is heated to a higher temperature (above 200°C), leading to complete dehydration of gypsum. Thus, it is not the product of heating at 130°C.
- **Option B:** This seems to represent an incomplete or incorrect formula and does not correspond to a commonly recognized phase of calcium sulfate.
- **Option D:** This option seems to suggest no change or possibly an incorrect representation, which does not align with the known products of gypsum calcination.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the temperature of calcination determines the product formed from gypsum. Specifically, heating gypsum (CaSO4·2H2O) at different temperatures yields **Plaster of Paris (CaSO4·½H2O) at around 130-150°C** and **Anhydrite (CaSO4)** at higher temperatures. This property is crucial in the manufacture of dental and orthopedic casts.
## **Correct Answer:** .