What is solvent extraction ?How it purify metal?
The process of solvent extraction based on the preferential solubility principle .That is solute can distribute itself in different ratio between two immicible solvents like organic solvents(Benzene,CCl4,ether etc)and inorganic solvents(H20)
In this method,the impure metal solution (aqueous solution) is treated with organic solvent (non-aqueous solution) which is immiscible to the solvent of metal ions but act as better solvent for the metal ion to be separated.
Example:
Germanium ions are separated from other ions by solvent extraction method.Germanium ions in aqueous solution is first converted into tetrachloride.Germanium chloride is less polar and dissolves in organic phase.when these aqueous solution is treated with CCl4 ,only Germanium tetrachloride is dissolves in CCl4 while other metal ion(impurity ) remains dissolved in water.In this way CCl4 extracted only Germanium chloride from the another solvent i.e water.
What is chromatography? Write its principle .
Chromatography is the modern technique which is used to separate almost all mixture either colour or colourless to test the purity of sample .This based on differences in some of their physical properties .Adsorption, parting between two immiscible solvents capacity to under go ion exchange process are important physical properties .
principle :
Chromatography based on the principle of selective distribution of the components of mixture between two phases.
fixed( stationary) phase and moving (mobile ) phase . Stationary phase can be solid or liquid while the moving phase is liquid or gas . When the stationary phase is a solid , the basis is adsorption and when it is liquid ,the basis is partition .
What is zone refining process ? Write the principle of zone refining process for refining metals ?
zone refining is the method of purifying metal in high degree of purity .This method is mostly used in purifying metals by removing an impurity .
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A circular moveable heater is fixed around a rod of impure metal to melt the impure metal over that portion .Then the heater is moved away slowly along the rod .When the molten metal cools then the pure metal crystallizes out , while the impurities remain in the liquid phase .Which pass out into the adjacent molten zone .In this way,the impurities are swept away to another end of rod with movement of heater .The impurities are finally discarded .The process are repeated several times to obtain pure metals Si,Ge,& Ga etc are purified by this process .This process is also called fractional crystallization. .