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General Science - Chemistry (Important points to remember)

Written By STPORTAL on Sunday, March 18, 2012 | 2:48 PM


General Science - Chemistry (Important points to remember):

·         Transuranium elements have not been found in nature and can only be produced artificially (having atomic numbers higher than 92).
·         Temporary hardness of water is due to the presence of bicarbonates of calcium and magnesium in water. Whereas the permanent hardness is due to the presence of Calcium Sulphate , which can be eliminated by the use of Zeolites i.e large group of minerals composed of hydrated aluminum silicates of alkali metals and alkaline earth metals such as stilbite, chabazite, natrolite, and analcime
·         The gas used in balloons is helium
·         A mixture of potassium chlorate and manganese dioxide is known as oxygen mixture.
·         gobar gas is obtained by decomposition of vegitable matter and animal dung.
·         L.P.G (liquefied petroleum gas) consists of mainly propane and butane.
·         Natural gas is composed primarily of methane and other light hydrocarbons.
·         Carbon Dating, method for determining the approximate age of ancient objects by measuring the amount of carbon 14 they contain.
·         Ethylene gas is used for artificial fruit ripening
·         Sodium and potassium react vigorously with cold water so it is preserved under kerosene while phosphorus is spontaneously inflammable in air so preserved  under water.
·         Nitrous oxide is called laughing gas, in mild doses it is used as anesthetic
·         Haber process is used to manufacture ammonia in which nitrogen and hydrogen are made to combine in the ratio 1:3 at high pressures of 200-900 atmospheres
·         Nitric acid is used as fertilizers and explosives
·         Tri-nitro toluene and nitro glycerene are common explosives
·         A mixture of 2,4,6 tri nitro toluene and ammonium nitrate is called amatol and is used as a blasting material
·         Nessler’s reagent – It is used as test for ammonia and ammonium salts in which it produces an yellow colour or brown precipitate is obtained.
·         Arc process or birkeland –eyde process is an important process for the manufacture of nitric acid, evolved during first world war (1914-1918) by German.
·         Smelling salt is ammonium carbonate
·         Compounds of nitrogen with metals are called nitrides
·         Sal ammoniac is ammonium chloride .
·         Battery electrolyte consists of a mixture of ammonium chloride and zinc chloride made into a paste.
·         Potassium nitrate or Nitre or Indian salt petre is used as Gun powder. Saltpeter is of commercial importance as a fertilizer, in the manufacture of glass, as a food preservative, and in some medicines as a diuretic. Saltpeter was once used in gunpowder and is now found in explosives, fireworks, and matches. In addition, this substance is employed in fluxes used in metallurgy. It is important as a source of nitrogen in the manufacture of nitrogen- containing compounds, particularly nitric acid, and as an oxidizing agent in many industrial chemical processes.
·         Chile saltpeter, or soda niter, is composed of sodium nitrate, NaNO3. It occurs over vast areas in South America, particularly in Chile.
·         Iron loses its property of liberating hydrogen from dilute acid and displacing other metals, when it is kept in contact with concentrated Nitric acid for some time . It is called passivity.
·         The common harmful gases are carbon monoxide from internal combustion engine, sulphur dioxide from industries and oxides of nitrogen from vehicles.
·         Dust particles from the cement factories are made to settle down by electrophoresis i.e. by huge electrodes on the top of the building carrying nearly a million volts of electricity.
·         Essential plant nutrients are Nitrogen, Phosphorus and Potassium (NPK)
·         Nitrogen is essential for rapid growth and increased yield of crops. Deficiency is indicated by yellowing of leaves. Phosphorous promote early growth and maturity of plants. Deficiency is indicated by purpling of leaves, ripening and fruiting is poor. Potassium develops a healthy root system. It deficiency is indicated by white,yellow and reddish brown spots on the leaves.
·         In the purification of water for drinking purposes, the suspended impurities such as clay and fine particles of sand are first coagulated by addition of the required quantity of aluminium sulphate which is known as filter alum
·         The paste applied to the side of a match box is a mixture of Phosphorous Trisulphide, glass powder and sand to cause frictions and glue. The match head contains a readily combustible substance like atimony trisulphide, an oxidizing agent like potassium chlorate which maintain the combustion and a binding material like glue.
·         Marble is calcium carbonate
·         Vinegar is acetic acid
·         Methylated spirit is a mixture of methyl alcohol and ethyl alcohol
·         Urea is the first organic compound prepared in the laboratory
·         Carbonic acid is soda water
·         Mercaptans – leakage in L.P.G cylinders is easily detected.
·         Hydrazine is used to propel rockets
·         Coke is obtained by healthy wood out of contact with air
·         1 Carat = 200 mg
·         Terylene and nylon are synthetic fibres produced by a process of polymerization. Terylene is a polyester and Nylon a polymide.
·         Pyrene is carbon tetrachloride specially used to extinguish electrical fires.
·         Tincture iodine is a solution of iodine in alcohol.
·         Soft water lather easily with soap.
·         Nickel is used in conversion of oil into solid fat.
·         The presence of dust particles in the air serves as a nucleaus to condense water vapour resulting in rain.
·         The substance that is found abundly in seawater is sodium chloride.
·         The metal, which reacts violently with cold water, is potassium
·         Pyrene is the commercial name for carbon tetrachloride
·         Glaubers salt is Na2SO4 10H20
·         Hypo is sodium thiosulphate extremely soluble in water
·         Hygroscopic substance is one which absorbs moisture from the air but does not turn into liqid. E.g. ethyl alcohol.
·         Coal gas is the product of destructive distillation of coal i.e. heating coal out of contact of air
·         Calgon is the trade name given to a complex salt sodium hexametaphosphate which removes calcium and magnesium present in the hard water thus making
 soft and fit for use in boilers.
·         The domestic cooking gas consists of mostly liquefied butane and isobutene
·         Manometer is the instrument for measuring the pressure of liquids and gases.
·         Rust is hydrated ferric oxide
·         The chief component of pearl is ferric component
·         the fibrous form of several minerals and hydrous silicates of magnesium. The name may also be applied to the fibrous forms of calcium and iron.
·         An ion is an electrically charged atom or molecule. Negatively charged ions are known as anions (which are attracted to anodes) while positively charged ions are known as cations (which are attracted to cathodes

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