Write the equation for the reaction of Plaster of Paris with water.

Reaction of Plaster of Paris with Water

Plaster of Paris is a material that undergoes a chemical reaction when mixed with water. The reaction is as follows:

$$\text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} + \frac{3}{2}\text{H}_2\text{O} \rightarrow \text{CaSO}_4 \cdot 2\text{H}_2\text{O}$$

In this reaction:

• CaSO₄ · ½H₂O is Plaster of Paris.
• CaSO₄ · 2H₂O is gypsum.

Explanation:

• When Plaster of Paris (calcium sulfate hemihydrate) is mixed with water, it reacts to form gypsum (calcium sulfate dihydrate).
• During this reaction, heat is released, which is an exothermic process. This heat release helps the plaster to set and harden.
• Plaster of Paris is prepared by heating gypsum (calcium sulfate dihydrate) to about 150°C, which removes part of its water content and transforms it into Plaster of Paris.

This reaction is widely used in construction, art, and medical applications due to the material’s ability to set quickly and harden.