Some Important Compounds

1. Ammonia
Uses
- Ammonia solutions are used to clean, bleach, and deodorize; to etch aluminum; to saponify (hydrolyze) oils and fats; and in chemical manufacture.
- Ammonia is also used in large amounts in the Ostwald process for the synthesis of nitric acid; in the Solvay process for the synthesis of sodium carbonate; in the synthesis of numerous organic compounds used as dyes, drugs, and in plastics; and in various metallurgical processes.
- The ammonia sold for household use is a dilute water solution of ammonia in which ammonium hydroxide is the active cleansing agent.
- As a constituent of smelling salt, it revives a fainted person. But it should be used with caution since it can attack the skin and eyes. The vapors are especially irritating prolonged exposure and inhalation cause serious injury and may be fatal.
- Ammonia and its compounds are mainly used as fertilizers.
- Liquid ammonia is used as refrigirant.
2. Sulphur Dioxide
Uses
- It is a powerful germicide and insecticide and hence it is used a household fumigant.
- It can bleach delicate fibres.
- It undergoes easy liquefaction and vaporization and hence it is used as refrigerent in cold storage plants.
- It is used in the manufacture of sulphuric acid by contact process
- It is raw material for manufacture of calcium bi sulphite used in treatment of wood pulp for paper industry.
- It is used in sugar industry for refining sugar.
3. Sulphuric acid
Uses
- In the manufacture of fertilizers, ammonium phosphate and calcium super phosphate.
- In the manufacture of rayon and nylon and also in the preparation of dyes and drugs from coal tar derivatives.
- In the manufacture of the explosives such as Tri-nitro toluene, Tri-nitro glycercineand picric acid.
- In the manufacture of nitric acid, hydrochloric acid and phosphoric acid.
- In the manufacture of sodium sulphate for glass industry and ferrous sulphate for ink industry.
- In the purification of petrol, kerosene, and lubricants.
- It is used in metallurgy for extraction of metals. Leaching of metallic compounds gives sulphates which on electrolysis gives the metal in pure form. It is used for pickling of metals.
- It is used in storage of batteries.
- It is used as a laboratory reagent for the preparation of iodine, carbon monoxide and hydrogen.
4. Sodium Carbonate (Na2C03)
Popularly known as washing soda or soda ash, sodium carbonate is a commercially important compound. In earlier days, it was obtained from the ash of plants and from natural deposits in India and Egypt.
Uses of Sodium Carbonate
Sodium carbonate is used :
- as washing soda in laundry as a cleansing agent
- for softening hard water
- in manufacturing glass, paper, soap and caustic soda
- as a valuable laboratory reagent
- in quantitative analysis to standardise acid solutions
- in qualitative analysis in the detection of acid radicals of insoluble salts
5. Sodium Bicarbonate (NaHC03)
Sodium bicarbonate is commonly called baking soda.
Uses of Sodium Bicarbonate
- Used in the preparation of carbon dioxide
- Used as a constituent of baking powder, and in effervescent drinks. Baking powder has sodium bicarbonate and tartaric or citric acid. When it is dissolved in water or heated carbon dioxide is produced. This carbon dioxide gas causes the puffiness and lightness of cakes, biscuits etc.
- Sodium bicarbonate is used to extinguish fire as it produces carbon dioxide gas.
- It is used to remove acidity. Due to its alkaline nature, it reacts with excess acid ~enerated in the stomach and neutralises it to relieve acidity.
6. Bleaching Powder (CaOCl2)
Calcium oxychloride is the chemical name of bleaching powder .
Uses
- Bleaching powder is commonly used for bleaching clothes.
- It is also used in bleaching wood pulp in the paper industry.
- It is used to disinfect drinking water.
- It is used in the manufacture of chloroform (CHCl3), an anaesthetic.
- It is used as an oxidising agent:
- It is used to shrink wool.
7. Plaster of Paris (CaSO4) 2.H2O
Chemically, plaster of paris is known as calcium sulphate hemihydrate (hemi means half).
Uses
- Plaster of Paris is used to set fractured bones due to its setting property on hydration.
- It is used as a sealant in laboratories.
- Can be used to make casts for toys, statues, ornaments and decorative items.
- It is used as a fire proofing material.
- Used in the manufacture of black-board chalk.
8. Cement
Portland cement is a very important building material. It was first discovered in England. It got its name because on setting, it hardened to a stone-like mass and was compared to the famous Portland Rock of England. It is a mixture of calcium and aluminium silicates with gypsum.
The approximate composition of cement is
Calcium oxide (CaO) = 50 - 60%
Silica (SiO2) = 20 - 25%
Alumina (Al2O3) = 5 - 10%
Magnesium oxide (MgO) = 2 - 3%
Ferric oxide (Fe2O3) = 1 - 2%
Sulphur trioxide (SO3) = 1 - 2%
9. Glass
Any amorphous and transparent solid that is a product of the solidification of a liquid is called glass. However, glass is generally referred to as the transparent substance obtained when white sand is fused with oxides and carbonates of alkaline earth metals and the molten mixture is cooled. Glass is a super cooled liquid i.e., it is a liquid cooled much below its freezing point. The ordinary room temperature is much below the freezing point of glass.
From Egypt to Alexandria to other European countries and the US, the history of glass dates back to the 17th century and before.
Manufacture of Glass
Raw Materials
- Silica (in the form of sand)
- Compounds of alkali metals, like Na2CO3, Na2SO4, NaNO3, K2CO3 and KNO3·
- Compounds of alkaline earth metals, like CaCO3, CaO, BaCO3. (for glass with high refractive index)
- Oxides of heavy metals, like PbO, Pb3O4
- Calcium phosphate, Ca3(PO4)2 (for opalescent glass that also contains arsenic and antimony oxides)
- Colouring materials - Metallic oxides like ferric oxide (yellow), chromic oxide (green), manganese oxide (purple) and cobalt oxide (blue) are added to fused silicates to get coloured glass.
Properties of Glass
As we have seen, glass is a mixture of number of silicates. Therefore, when heated, it does not melt at a fixed temperature. But, it softens gradually and hence can be moulded into any desired shape. It is this property that makes glass one of the widely used materials.
Annealing
Glass if cooled rapidly becomes brittle and fragile and if cooled very slowly becomes opaque because of devitrification. For this purpose, before making articles, glass is passed through a long tunnellike furnace that is very hot at one end and very cold at the other. When glass is passed through this furnace, it is progressively cooled. This process is known as annealing and takes several days to be completed.
Varieties of Glass
I. Soda Glass
Otherwise known as soft glass
- Composition
Sand /Quartz : SiO2 : 75% (will be nice if this can be a mouse over)
Sodium Oxide: Na2O : 15%
Calcium Oxide: CaO : 8%
Aluminium Oxide: Al2O3 : 2% (impurity)
Uses
Since it softens at a comparatively lower temperature and can be shaped into different forms, it finds use in making windowpanes, bottles, etc.
II. Potash Glass (Hard Glass)
- Composition
Sand /Quartz : SiO2
Potassium oxide: K2O
Calcium Oxide : CaO
Aluminium Oxide: Al2O3
Uses
Has a higher melting point and can withstand higher temperature. Hence it finds use in laboratory ware.
III. Flint Glass
- Composition
Silica: 45%
Sodium oxide: 4%
Potassium oxide: 4%
Calcium oxide: 3%
Lead oxide: 44%
Lead carbonate or oxide replaces calcium carbonate. Potassium carbonate partly replaces sodium carbonate
Uses
It has higher density, transparency and refracting power than ordinary glass. Hence used for making optical instruments. It is also used for ornament purposes.
IV. Pyrex Glass
- Composition
Silica : 80%
Sodium oxide : 4%
Calcium oxide : 0.5%
Potassium oxide : 0.5%
Boron trioxide : 12%
Aluminium trioxide : 3%
Uses
It has very low co-efficient of expansion and can withstand sudden changes in temperature. Therefore highly suitable for laboratory ware like flasks, beakers and oven proof cook wares.
V. Jena Glass
- It has lesser alkaline and higher alumina content than soda glass. It also contains barium oxide, zinc oxide and boron trioxide instead of silica.
Uses
More resistant to the action of acid or alkali. Hence can be used to make acid and alkali containers.
VI. Crooke's Glass
- Contains cerium oxide as one of the constituents as one of the constituents.
Uses
It is used for optical purposes as it has the capacity to cut off the ultra violetrays.
VII. Safety Glass or Unbreakable Glass
- It is prepared by placing a layer of transparent plastic (sheet of vinyl acetate resin) between two layers of glass and sealing the layers with adhesive.
Uses
This variety of glass does not break easily under ordinary impact. Even though it breaks under heavy impact, glass pieces are not shattered because they are held by plastic. Therefore it is used in making windscreens of automobiles, aeroplanes and trains. It can also serve as bullet proof glass to some extent.
10. Steel
Carbon content of steel is between 0.1 and 1.5%. This is intermediate between cast iron and wrought iron. The hardness of steel increases with increase in carbon content. Steel contains other elements like manganese, chromium, silicon, nickel, tungsten, vanadium, and molybdenum. These elements are added for making steels of different kinds.
Properties of Steel
The properties of steel dep,end on the carbon content and the heat treatment imparted to it.
If the carbon content is low, the steel is soft and ductile and is called mild steel. As the carbon content increases, the dl:lctility decreases, but the tensile strength increase upto 1.5% of carbon content. After that it decreases.
Steel melts at a lower temperature than wrought iron. Adding a little manganese imparts elasticity to steel and if 10% manganese is added, steel becomes very hard. It can be used in making mechanical crushers.
Adding chromium makes steel chemkally resistant and is used as stainless steel in utensils, cutlery, surgical tools etc.
Heat Treatment of Steel
The hardness and elasticity of steel can be controlled by heat treatment. When it is heated to redness and then allowed to cool slowly, it becomes soft. This process is known as annealing.
If it is cooled suddenly by plunging into ice-cold water (quenching), steel becomes very hard and brittle. On reheating to 250° - 300°C, the brittleness disappears but the hardness is retained.
The degree of hardness can be controlled by heating the product once again to a temperature ranging from 200° to 350°C and then allowing it cool slowly. This is caned tempering. Based on the temperature, the colour of the oxide film formed on the surface varies.
Temperature
Colour
230°C
Pale yellow
260°C
Brown
280°C
Purple
300°C
Blue
Colour of oxide film formed due to tempering of steel
Case Hardening
When wrought iron absorbs carbon at the surface, its surface becomes hard. This is called case-hardening. This can also be done by heating wrought iron and potassium ferrocyanide. A surface layer of steel is formed on wrought iron. This is used to make armour plates and parts of machinery that face constant wear and tear.
Nitriding
When steel (containing 1% of aluminium) is heated in an atmosphere of ammonia at 550°C -600°C, the surface of steel becomes very hard. This is called nitriding. Nitrogen formed by the dissociation of ammonia reacts with iron and aluminium to form the respective nitrides on the surface. These nitrides settle in the interstices (an intervening space, crevice) of the iron crystals resulting in a compact and hard surface.
11. Calcium Oxide (CaO)
Calcium oxide is commonly called Qukk Lime. Quick lime has always been a cheap commodity because limestone deposits are readily available. Lime manufacturing and application dates back to the Roman, Greek and Egyptian civilizations.
Uses of Lime
- Lime is indispensable for use with mortar and plaster.
- Lime is used for medicinal purposes, insecticides and plant and animal food.
- It is used as a laboratory reagent for gas absorption, precipitation, dehydration etc.
- It is used as a reagent in the manufacture of paper, high grade steel and cement.
- If finds use in dehairing hides.
- It can be used for water softening and in the recovery of ammonia (byproduct of Solvay process).
- It finds enormous use in the manufacture of soap, rubber, varnish, refractories and lime bricks.
- It also finds use in the preparation of calcium carbide, basic calcium nitrate and calcium bisulphite.
- Improves the quality of soil.
12. Slaked Lime Ca(OH)2
When calcium oxide reacts with water, it liberates heat and cracks into a white powder. This white powder is calcium hydroxide or slaked lime. The process is called slaking of lime.
Uses
Calcium hydroxide is used for:
- Testing carbon dioxide (CO2) in laboratories. It turns milky when carbon dioxide is passed into it due to the precipitation of calcium carbonate (CaCO3)·
- White washing buildings. This reacts slowly with carbon dioxide (CO2) in the air to form calcium carbonate (CaCO3) on the walls and give a bright appearance.
- Making mortar when mixed with sand and water.
- Preparing bleaching powder, caustic soda (NaOH) and ammonia (NH3).
- Reducing acidity of soil.
- Softening temporary hard water'.
- Tanning leather.
Summary
Common name
Chemical name
Formula
Washing soda
Sodium carbonate decahydrate
Na2CO3.10H2O
Bakin soda
Sodium bi carbonate
NaHCO3
Quick lime
Calcium oxide
CaO
Bleaching powder
Calcium oxychloride
CaOCl2
Slaked lime
Calcium hydroxide
Ca(OH)2
Plaster of Paris
Calcium sulphate hemi hydrate
(CaSO4)2.H2O
Gypsum
Calcium sulphate dihydrate
CaSO4.2H2O
Dead burnt plaster
Calcium sulphate anhydrous
CaSO4
Lime stone
Calcium carbonate
CaCO3
Some of the important compounds of sodium and calcium were discussed in this chapter. It may be understood that the properties of similar compounds of other elements in Group I and Group II will resemble the properties of the compounds discussed in this chapter. The fact that the elements are classified in groups help us in understanding their properties and therefore their applicationin a better perspective.