Question 12.23 Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.
Class XI Organic Chemistry : Some Basic Principles and Techniques Page 363
Class XI Organic Chemistry : Some Basic Principles and Techniques Page 363
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PRINCIPLE OF ESTIMATION OF HALOGENS :A known mass of the organic compound is heated with fuming nitric acid and a few Crystal of silver nitrate is a sealed hard glass tube .
under the conditions , carbon and Hydrogen are oxidised to carbon dioxide and water respectively while halogens is converted into silver halide . the participate of silver halide is filtered , washed , dried and weighed . knowing the mass of the substance taken and the mass of precipitate formed , the percentage of halogens is calculated as follow,
% of X = (atomic mass of X/molecule mass of AgX) × {mass of AgX formed /mass of substance taken } × 100
PRINCIPLE OF ESTIMATION OF SULPHUR :-
A known mass of the substance is heated with sodium peroxide or fuming nitric acid in a sealed tube . carbon and Hydrogen are oxidised to CO2 and H2O respectively. while sulphur present in the compound is oxidised to H2SO4 which is them precipitated as Barium sulphate by adding of barium chloride solution.
The PPT of BaSO4 is filtered , washed , dried and weighed . knowing the mass of the substance taken and the mass of BaSO4 ppt formed ,
% of S = {32/233} × { mass of BaSO4 formed/mass of substance taken } × 100
PRINCIPLE OF ESTIMATION OF PHOSPHORUS:- a known mass of organic substance is heated with fuming nitric acid in a sealed tube . under these conditions , C and H are oxidised to CO2 and H2O respectively. while Phosphorus present in organic compound is oxidised to H3PO4 which is precipitated as ammonium phosphomolybadate by heating it with conc.HNO3 and then adding ammonium molybdate.
The precipitated of amm. phosphomolybadate are filtered , washed , dried and weighed .
% of P = {31/1877} × {mass of amm. phosphomolybadate formed /mass of substance taken} × 100