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The metals prepared by different methods contain impurities. The methods used for the purification of metals are called refining. The refining method depends on the nature of metal and the nature of impurities. Some common methods are as follows 1. Distillation Volatile metals like zinc and mercury are purified by boiling the impure metal to get vapors of the pure metal which is condensed and collected. 2. Liquation Low melting metals like tin and lead are purified by this method. The impure metal is melted on the sloping floor of a furnace. The metal melts and flows down leaving behind the high melting impurities. 3. Poling Impure metal is melted and stirred with green logs of wood. The impurities rise to the surfaces, get oxidised and removed as gases (CO2) or slag. The metal may get oxidised (eg:- Cu to Cu2O). The hydrocarbons in green wood reduces the metal oxide to the metal. Example:- Refining of impure Cu and Sn. 4. Cupellation Impure silver and gold contain base metals like lea...

Mercury forms halides in the two oxidation states, +1 and +2. 1. Mercury(1)Chloride(Hg2Cl2) Mercury(1) chloride or mercurous chloride is known as calomel. Preparation Mercury(1)chloride is prepared by heating a mixture of mecury(2)chloride and mercury in iron vessel. HgCl2 + Hg -------> Hg2Cl2 It can also be obtained by reduction of mercury(2)chloride by reducing agents like tin(2)chloride in limited quantity. 2HgCl2 + SnCl2 --------> HgCl2 + SnCl4 Properties When heated, mercury(1)chloride decomposes into mercury(2)chloride and mercury. Hg2Cl2 -------> HgCl2 + Hg The action of aqueous ammonia on the solid mercury(1)chloride gives a mixture of black finely divided mercury and white mercury amino chloride. This reaction is an example of disproportion reaction. Hg2Cl2 + 2Nh3 -------> Hg(NH2)Cl + Hg + NH4Cl Uses of mercury(1)chloride Calomel is used in making standard calomel electrodes used as secondary reference electrode. It is also used as a purgative in medicines. 2. Merc...

Preparation Silver nitrate is prepared by dissolving silver in dilute nitric acid. 3Ag + 4HNO3 ------> 3AgNO3 + 2H2O + NO Properties Silver nitrate on heating decomposes to form silver, nitrogen dioxide and oxygen. 2AgNO3 ---------> 2AgNO2 + O2 AgNO2 ---------> Ag + NO2 Silver nitrate is also decomposed by organic matter, such as glucose, paper, skin and cork. It has also a caustic and destructive effect on organic tissues. Uses of silver nitrate Large quantities of silver nitrate are used in the production of light sensitive plates, film and papers. In the laboratory it is used as a reagent for the detection of halide ions. It is used in making inks and hair dyes. In small doses, silver nitrate is used as a medicine for nervous diseases. Silver halides Silver fluorides may be prepared by the action of hydrofluoric acid on silver(1) oxide. Ag2O + 2HF -------> 2AgF + H2O Silver chloride, silver bromide and silver iodide are prepared by the action of silver nitrate on sodium ...

Copper sulphate penta hydrate is known as blue vitirol and is the most common oxosalt of copper(2) Preparation Copper sulphate is prepared industrially by blowing a current of air through copper scrap and dilute sulphuric acid. 2Cu + 2H2O + O2 --------> 2CuSO4 + 2H2O The crude copper(2) sulphate solution obtained contain iron(2) sulphates as impurity Dilute nitric acid is added to oxidize iron(2) to iron(3) sulphate which remains in solution after crystallization and CuSO4 5H2O crystallizes out. The crystalline copper(2) sulphate, CuSO4 5H2O has the structure in which four water molecules are coordinated to the central copper cation in square planar structure. The fifth water molecule is held by hydrogen bonds between a sulphate anion and a coordinated water molecule. The fifth hydrogen bonded water molecule is deeply embedded in the crystal lattice and hence not easily removed. Properties 1. Copper sulphate penta hydrate is a blue coloured crystalline solid, soluble in water. 2. Ac...

The reaction between an acid and a base is called neutralization. It is very fast and the equilibrium constant for a neutralization reaction is so large that it nearly proceeds to completion. An acid-base titration is a simple and convenient volumetric method for quantitatively estimating the concentration of one, if that of the other is known. A known volume of the solution of an acid or base is transferred to a titration flask with the help of a pipette. we add indicator and start adding known volumes of the other solution in steps with the help of a burette. The point at which the reaction is observed to be complete is called the end point of the titration and is noted by the change in the colour of the indicator. For accurate estimation it is necessary for it to coincide with the equivalence point corresponding to the stoichiometric amounts of the acid and base in the neutralization reaction. A number of weak organic acids and bases which can change its colour with in...