Question

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

Answer 1

Hint: POP or Plaster of Paris is a white powder which is mostly used for beautification of ceilings of houses and buildings and for making statues, toys, blackboard chalk. It contains the elements calcium, sulfur, oxygen and hydrogen as constituent particles.

Complete step by step answer:
 - The chemical name of Plaster of Paris or POP is Calcium sulfate hemihydrate and the hemihydrate part is due to the half molecule of water which is attached to the calcium sulfate molecule. From the chemical name the chemical formula can be written as $CaS{{O}_{4}}.{1}/{2}\;{{H}_{2}}O$.

- The POP is prepared by heating gypsum (Calcium sulfate dihydrate) at a temperature around 373 kelvin. The Plaster of Paris has a property of setting into hard mass when it’s treated with water and this setting is due to the hydration to form crystals of gypsum. This setting of Plaster of Paris can be represented as follows
\[\underset{Plaster\text{ }of\text{ }Paris}{\mathop{CaS{{O}_{4}}.{1}/{2}\;{{H}_{2}}O}}\,+\underset{Water}{\mathop{{3}/{2}\;{{H}_{2}}O}}\,\to \underset{Gypsum}{\mathop{CaS{{O}_{4}}.2{{H}_{2}}O}}\,\]

- The advantages of Plaster of Paris can be given as follows
(i) POP is more durable and is light in weight
(ii) It has low thermal conductivity
(iii) POP will not cause cracking of surfaces
(iv) A very good insulating material since it’s a very good fire resistant
(v) POP is used in hospitals for setting the fractured bones into the right position
(vi) Used in chemical laboratories for sealing the air gaps in apparatus for air tight arrangement
(vii) Used for giving a decorative interior finish on buildings.

Note: Keep in mind that the Plaster of Paris is one of three types of plaster. The other two types of plasters are lime plaster, which is made from calcium hydroxide and sand, and cement plaster, which is the combination of sand, plaster, Portland cement and water. Among these three, POP is the most commonly used plaster and is also known as gypsum plaster.