Which one of the following is correct ? Setting of Plaster of Paris is

The setting of Plaster of Paris (calcium sulfate hemihydrate) is a chemical process involving hydration. When Plaster of Paris is mixed with water, it undergoes a hydration reaction to convert back into gypsum (calcium sulfate dihydrate) [c1][t2]. This reaction is represented by the chemical equation: CaSO4·0.5H2O + 1.5H2O → CaSO4·2H2O [c1][t4]. The process is exothermic and leads to the formation of a hard, solid mass characterized by an interlocking network of gypsum crystals [t2][t5]. This transformation is specifically a 'hydration leading to another hydrate' because the hemihydrate reactant incorporates water molecules into its crystalline structure to form the dihydrate product [t2][t7]. Unlike other calcium compounds like lime, it does not set by reacting with atmospheric CO2 or oxygen [c3][c5].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Plaster of Paris > p. 33
2. [2] https://www.sciencedirect.com/science/article/abs/pii/S0960897407000034
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > QUESTIONS > p. 7
4. [4] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > 2.1.6 Reaction of a Non-metallic Oxide with Base > p. 22