Question

Fill in the following blanks:
(a) Common salt is obtained from sea-water by the process of ...........
(b) Rock salt is mined just like......................
(c) Chemical formula of washing soda is..................
(d) Sodium hydrogen carbonate is .................. soda whereas sodium carbonate is................. Soda.
(e) The chemical formula of plaster of Paris is............

Answer 1

Hint:Salts dissolved in seawater are non volatile. Baking soda is sodium hydrogen carbonate and washing soda is sodium carbonate. Plaster of Paris is hemihydrate calcium sulphate.

Complete step by step solution:
a.Common salt or sodium chloride is obtained from sea water by the process of evaporation. As being non volatile, it does not go into vapour state on heating. Seawater contains many salts dissolved in it. Sodium chloride is further separated from these salts.
b.Sea water contains many salts. These salts are non volatile. When crystals of these salts mix with large impurities, it forms a brown coloured substance. This is known as rock salt. Beds of rock salts were formed when seas of bygone ages dried up and left behind only large sized rock salt. Rock salt is mined like coal.
c.Baking soda or \[{\text{NaHC}}{{\text{O}}_3}\] (sodium hydrogen carbonate) is commonly used in the kitchen on a regular basis. It produces sodium carbonate and carbon dioxide on heating. Being alkaline, it is used as antacids. It is also used in soda-acid fire extinguishers. Washing soda or \[{\text{N}}{{\text{a}}_2}{\text{C}}{{\text{O}}_3}\] (sodium carbonate) is also a basic salt. It is used in glass, soap and paper industries. It is also used to remove permanent hardness of water.
d.Plaster of Paris is calcium sulphate hemihydrate salt. Its chemical formula is \[{\text{CaS}}{{\text{O}}_4}.\dfrac{1}{2}{{\text{H}}_2}{\text{O}}\] . It is formed by heating of gypsum. It is used in making statues, supporting fracture purposes in hospitals & by dentists to make dental models. It is a white coloured salt & again changes to gypsum on mixing with water.
e.Thus common salt is obtained from seawater by the process of evaporation. Rock salt is mined like coal. Chemical formula of washing soda is \[{\text{N}}{{\text{a}}_2}{\text{C}}{{\text{O}}_3}.10{{\text{H}}_2}{\text{O}}\] . Sodium hydrogen carbonate is baking soda & sodium carbonate is washing soda. The chemical formula of plaster of Paris is \[{\text{CaS}}{{\text{O}}_4}.\dfrac{1}{2}{{\text{H}}_2}{\text{O}}\].

Note:
In Hydrated salts like \[{\text{CaS}}{{\text{O}}_4}\] , water gives shape and colour and is called water of crystallization. In plaster of Paris, two molecules of \[{\text{CaS}}{{\text{O}}_4}\] share one molecule of water.