Saved Bookmarks
| 1. |
How will you estimate phosphorous in an organic compound? |
|
Answer» Solution :Carius method: Procedure: A known mass of organic compound (wg) containing PHOSPHORUS is heated with fuming `HNO_(3)` in a sealed TUBE where C is converted into `CO_(2)` and H to `H_(2)O`. PHOSPHOROUS present in the organic compound is oxidised to phosphoric acid which is precipitated as AMMONIUM phospho molybdate by heating with CONC. `HNO_(3)` and by adding ammonium molybdate. `H_(3)PO_(4) + 12 (NH_(4))_(2)MoO_(4) + 21 HNO_(3) overset(Delta)rarr(NH_(4))PO_(4).12 MoO_(3) +21NH_(4)NO_(3) + 12H_(2)O` The precipitate of ammonium phrospho molybdate is filtered, washed, dried and weighed. Calculation: Mass of organic compound=W g Mass of ammonium phospho molybdate= x g Molar mass ammonium phospho molybdate= 1877 g 1877 g of ammonium phospho molybdate contains 31 g of phosphorous `:. "x g of ammonium phospho molybdate contain"=(31)/(1887) xx x "g of phosphorous"` `:. "% of phosphorous"=((31)/(1887) xx (x)/(w) xx 100)% "of phosphorous"` In an alternate nethod, phosphoric acid is precipitated as magnesium-ammoniumphosphate by adding magnesia mixture. The ppt. is washed dried and ignited to get magnesium pyrophosphate which is washed, dried and weighed. Weight of magnesium pyrophosphate= y g Molar mass of magnesium pyrophosphate = 222 g 222 g of magnesium pyrophosphate contains 62g of P `:. "y g of magnesium pyrophosphate contain" = (62)/(222) xx y "g of P"` `"% of phospłorous" = ((62)/(222) xx (y)/(w) xx 100)%` |
|