Question

Write chemical formula of plaster of Paris (POP) and its advantages also.

Answer 1

Hint: Plaster of Paris is calcium salt with water of crystallization in it. It can be moulded and given any shape, light weight and many such properties will define its uses and application, and that will tell us about advantages.

Complete step by step answer:

The formula of Plaster of Paris is $CaS{O_4}.\dfrac{1}{2}{H_2}O$
Its name is calcium sulphate hemihydrate. It has half a molecule of water of crystallization.
The Plaster of Paris finds multiple uses like for making ceilings, certain places to make heat and cold resistant, medical applications, statues, designs and etc. This is mainly because of its property that it sets into hard mass, when mixed with water, and initially it is flexible and mouldable to give any shape, size and design, but after some time, it sets and becomes hard mass.
Its advantages are:
1. Easy to mould and reshape, so used for ceiling decoration or making decorative items.
2. Light weight.
3. Fire and heat resistant, so used for making ceilings in house to keep heat away.
4. Due to setting nature after some time into hard mass, it can be used for filling cracks and small holes wherever applicable.
5. Durable and long lasting.

Additional information: 

> The formation of Plaster of Paris is done by heating Gypsum under controlled condition.
> Gypsum is Calcium Sulphate dihydrate.
The reaction is as under:

\[CaS{O_4}.2{H_2}O\xrightarrow{{Heat({{150}^0}C)}}CaS{O_4}.\dfrac{1}{2}{H_2}O + 1\dfrac{1}{2}{H_2}O\]
If overheating is done, then dead plaster of Paris is formed which cannot be used and has to be thrown.
If Plaster of Paris is added with limited water, then it becomes Gypsum and sets into hard mass after 10 minutes to 45 minutes. Gypsum finds wide application and uses when mixed with sand, soil, clay and water with proper proportion, and is widely used for making sculptures, statues and home decoration items and many more things.

Note:
Overheating of Gypsum will result in dead Plaster of Paris, which cannot be used. Thus, controlled heating is essential and the water of crystallization is reduced by one and half from Gypsum.