Useful Compounds Of Metals

Some Useful Compounds of Metals: Common Salt: Common salt is sodium chloride (NaCl). Common salt, when kept open, absorbs moisture from air. This is because of the presence of magnesium chloride in common salt. Magnesium chloride is deliquescent, that is, it absorbs water.

Sodium chloride is very important chemical. It is an essential ingredient in our daily meal. It can be converted into useful chemicals like caustic soda, washing soda and baking soda. It also yields hydrochloric acid, an important chemical used in chemical industry, and chlorine, which is used as a bleaching agent.

Caustic Soda: Chemically, caustic soda is sodium hydroxide (NaOH). It is obtained by electrolysis of brine (NaCl solution).

Washing Soda: Washing soda is sodium carbonate decahydrate $Na_2CO_3.10H_20$ . Sodium carbonate (soda ash) is alkaline in nature and has detergent (cleaning) properties. In a crystalline state, it possesses water crystallisation. On exposure to air, crystals lose water and turn into white opaque powder. Sodium carbonate is used as a cleansing agent for domestic purposes. It is also used for softening of hard water, in manufacturing of chemical like borax, caustic soda, glass and water glass. It is a constituent of many dry soap powders.

Baking Soda: The chemical name of baking soda is sodium hydrogen carbonate ( $NaHCO_3$ ). Sodium bicarbonate is used in the manufacture of baking powders and health salts.

Lime Calcium oxide is commonly known as quicklime or just lime. It is prepared by heating limestone ( $CaCO_3$ ) in a kiln.Calcium oxide reacts vigorously with water producing slaked lime [ $Ca(OH)_2$ ], which is used for making mortar and for white washing.

A solution of slaked lime is known as lime water, which is used for testing carbon dioxide. Calcium oxide is used for making cement and glass.

Bleaching Powder: The chemical name of bleaching powder is calcium oxychloride ( $CaOCI_2$ ). Bleaching powder is commonly used for bleaching in laundries. It is used in paper and textile industries, for disinfecting water and preparation of chloroform.

Plaster of Paris: It is a calcium sulphate hemihydrate [ $(CaSO_4)_2 H_2O$ ].

Faster of Paris has a remarkable property of hardening when mixed with proper quantity of water.The hardening of Plaster of Paris is due to its hydration to form gypsum. It is used in the laboratories for sealing the gaps, where sunlight arrangement is required. It is also used for making casts for statues, and in surgery to maintain joints in a fixed position.