Question

Write the chemical name, formula, and two main uses of Plaster of Paris.

Hint:

POP sets quickly when mixed with water and converts back to gypsum. That is why it is ideal for casts and moulds.

Answer 1

Concept: Plaster of Paris (POP) is a white powder obtained by heating gypsum at a controlled temperature. It is widely used due to its property of setting quickly when mixed with water. Chemical Name and Formula:

• Chemical Name: Calcium sulphate hemihydrate
• Chemical Formula: \( \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} \)

It is prepared by heating gypsum: \[ \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \xrightarrow{100^\circ C - 120^\circ C} \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} + \frac{3}{2}\text{H}_2\text{O} \] Main Uses of Plaster of Paris:

• Medical Use: Used for making casts to support fractured bones because it sets quickly and becomes hard.
• Decorative and Moulding Work: Used in making statues, toys, decorative items, and moulds for pottery and ceramics.

Conclusion: Plaster of Paris is calcium sulphate hemihydrate, widely used in medicine and moulding due to its quick-setting property.