Question

(a) What is the common name of the compound \[Ca{\left( {OCl} \right)_2}\] ?
(b) Name the raw material used for the preparation of plaster of Paris.
(c) Which property of plaster of Paris is utilized in making casts of broken limbs in hospitals?
(d) Explain why chlorine is used for sterilizing drinking water supply.

Answer 1

Hint: The questions mentioned are related to compounds of chlorine or chlorine itself. These compounds have common names as they are widely used in various applications. The common name of \[Ca{\left( {OCl} \right)_2}\] is the same as the name of the inorganic compound which is used as a bleaching agent in our homes. Plaster of Paris is a white powder which is very fine. It hardens when moistened. Chlorine and chlorine-based compounds have a very important property: they are used as disinfectants.

Complete answer:
Let us look at the questions one by one:
(a) \[Ca{\left( {OCl} \right)_2}\] is called Calcium hypochlorite, Calcium oxychloride, Calcium salt of hypochlorous acid, the chloride of lime, and various other names, but its common name is bleaching powder.

(b) The raw material used for preparation of plaster of Paris (POP) is Gypsum. Gypsum is a soft sulphate mineral with the formula \[CaS{O_4}.2{H_2}O.\] It is converted to plaster of Paris $\left( {CaS{O_4}.\dfrac{1}{2}{H_2}O} \right)$ on heating at $373K:$
\[CaS{O_4}.2{H_2}O\xrightarrow{{373K}}\,\,\,CaS{O_4}.\dfrac{1}{2}{H_2}O\,\,\, + \,\,\,\,1\dfrac{1}{2}{H_2}O\]

(c) The property of plaster of Paris is utilized in making casts of broken limbs in hospitals is that it can set into a hard mass within $30$ minutes of mixing with a particular quantity of water. This hardening of the cast will allow you to immobilize the broken limb, which will help in correcting deformities. When the particular quantity of water is added, POP $\left( {CaS{O_4}.\dfrac{1}{2}{H_2}O} \right)$ turns into gypsum $\left( {CaS{O_4}.2{H_2}O} \right)$ and becomes hard.
\[\,\,\,CaS{O_4}.\dfrac{1}{2}{H_2}O\,\,\, + \,\,\,\,1\dfrac{1}{2}{H_2}O \to CaS{O_4}.2{H_2}O{\text{ }}\]

(d) Chlorine is used for sterilizing drinking water supply as it has the ability to kill bacteria, viruses and parasites and completely disinfect water. This process is called Chlorination.

Note:
Bleaching powder has a strong smell of chlorine. Some common uses of bleaching powder in households are: as disinfectants, as an oxidizer, as a bleaching agent et cetera. The process of Chlorination usually kills off the pathogen in the water, making it potable. Sometimes, after chlorination, the water can smell or taste of chlorine.