Study of some important salts - class-XI

Super phosphate of lime is a mixture of two salts calcium dihydrogen phosphate $Ca\left( { H } _{ 2 }{ PO } _{ 4 } \right) _{ 2 }$ and calcium sulfate dihydrate ${ CaSO } _{ 4 }\cdot { 2H } _{ 2 }O$

First by filtration sand can be separated from the mixture of sand, salt and water. Then by evaporation the water will get evaporated leaving behind the salt. The evaporated vapours can be collected and condensed to get water.

Salt plays a primary role in the process of digestion and absorption. Salt plays a role in digestion by helping to break down food. It creates hydrochloric acid which is very important digestive secretion lining the stomach walls. Salt helps the body to digest food.

Gypsum is a mineral and is hydrated calcium sulfate in chemical form. Gypsum plays a very important role in controlling the rate of hardening of the cement. During the cement manufacturing process, upon the cooling of clinker, a small amount of gypsum is introduced during the final grinding process.

Gypsum is added to control the “setting of cement”. If not added, the cement will set immediately after mixing of water leaving no time for concrete placing.

Gypsum plays an important role in controlling the rate of hardening of the cement. During cement manufacturing process upon cooling of clinker a small amount of gypsum is added during the final grinding process. Gypsum controls the setting of the cement and if not added the cement will set immediately leaving no time for concrete placing.

 $MnO _2$which is black, is used to remove the green color from the glass and imparts purple tint to the glass. $Cr _2O _3$ imparts dark green colour, $Cu _2O$ produces a turquoise color, and $AuCl _3$ gives ruby red coloured glass.

In the manufacture of Portland cement, clinker occurs as lumps or nodules, usually $3: mm \ (0.12: in)$ to $25\ mm (0.98: in)$ in diameter, produced by sintering (fused together without melting to the point of liquefaction) limestone and alumino-silicate materials such as clay during the cement kiln stage. Gypsum is not present in it. 

Sodium hydroxide is used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents and as a drain cleaner.

Light sensitive compounds are used in photography for developing films. Halides of silver like silver chloride and silver bromide shows such kinds of properties therefore used in photography. 

Chile saltpetre(Sodium nitrate), is a deliquescent crystalline sodium salt. Nitre is potassium nitrate. They are used in the manufacture of gun powder, nitric acid etc. It is a mixture of sulfur, charcoal, and potassium nitrate (saltpeter).

A. Baking soda is sodium hydrogen carbonate which is prepared by Solvay process which is the reaction of sodium chloride,ammonia and carbon dioxide in water. The calcium carbonate is used in the reaction to get carbon dioxide gas.
${ CaCO } _{ 3 }\rightarrow CaO+{ CO } _{ 2 }\ { 2NH } _{ 3 }+{ CO } _{ 2 }+{ H } _{ 2 }O\rightarrow \left( { NH } _{ 4 } \right) _{ 2 }{ CO } _{ 3 }+{ CO } _{ 2 }+{ H } _{ 2 }O\rightarrow { NH } _{ 4 }{ HCO } _{ 3 }\ { NH } _{ 4 }{ HCO } _{ 3 }+NaCl\rightarrow { NaHCO } _{ 3 }+{ NH } _{ 4 }Cl$
B. Washing soda is sodium carbonate which is prepared from the sodium chloride.
$2NaCl+{ CaCO } _{ 3 }\rightarrow { Na } _{ 2 }{ CO } _{ 3 }+Ca{ Cl } _{ 2 }$

A. Bleaching powder is calcium hypochlorite
${ 2CaOCl } _{ 2 }+{ H } _{ 2 }{ SO } _{ 4 }\rightarrow { CaCl } _{ 2 }+{ CaSO } _{ 4 }+2HClO\ HClO\rightarrow HCl+\left[ O \right] \xrightarrow { Coloured\quad matter } Colourless\quad product$
B. Baking soda is sodium bicarbonate which is basic in nature and used as an antacid.
${ NaHCO } _{ 3 }$
C. Sodium carbonate which has a common name washing soda, a monohydrate which is used in the preparation of glass. It is used to flux silica by lowering down the temperature.
Two forms of sodium carbonate are used i.e heavy and light. The light form is obtained first and is converted to heavy form. The heavy form is is used as a solid in making glass where it is used as flux in the melting of silica.${ Na } _{ 2 }{ CO } _{ 3 }\cdot { H } _{ 2 }O$
D. The electrolysis of aqueous solution of sodium chloride gives hydrogen at the cathode and chlorine at the anode. This solution is called as the brine solution. It helps in the evolution of hydrogen gas and chloride gas.

Bone ash is Tricalcium phosphate in the form of hydroxyapatite ${ Ca } _{ 5 }\left( OH \right) { \left( P{ O } _{ 4 } \right)  } _{ 3 }$. Phosphoric acid is obtained from hydroxyapatite when treated with sulphuric acid.
$2{ Ca } _{ 5 }{ \left( P{ O } _{ 4 } \right)  } _{ 3 }OH+10{ H } _{ 2 }S{ O } _{ 4 }+18{ H } _{ 2 }O\longrightarrow 6{ H } _{ 3 }P{ O } _{ 4 }+10CaS{ O } _{ 4 }.2{ H } _{ 2 }O$

1. Liquid sodium metal is used as coolant in nuclear reaction
2. Potassium stearate is used in soft soap
3. Potassium nitrate is explosive
4. Potassium superoxide, which gives off oxygen as it absorbs carbon dioxide is used in Breathing apparatus in submarine

Bleaching powder $(CaOCl _2)$ has many uses and some of them are as follows :-

Sodium chloride$(NaCl)$, also known as common salt is used in food. It is obtained by evaporation of sea water.

Calcium hydroxide on reaction with chlorine produces bleaching powder.