Question

orthophosphates (PO4 3-) is determined by weighing as ammonium phosphomolybdate , (NH4)PO4.12MoO3. calculate the percentage of P2O5 in the sample if 1.5566 g precipitate was obtained from a 0.2500 g sample.

Answer 1

this concept is ignition method ,finally it is converted to Mg₂P₂O₇     quantitatively on ignition

      P₂O5 _{$\rightarrow$} Mg₂ P₂O_{7   ;        GIVEN}   W sample =0.2500 g ,w ppt =1.5566 g; Mwt of P₂O₅ =142 g

mwt of Mg₂ P₂O7 ₌=222g      

   percentage of P₂O₅ =    P₂O_{5 *} Wt of   ppt *                    * 100

                                       mwt of Mg₂P₂ O_{7   * W}t of the sample

                                   =142    *1.5566   * *100         =398.265    %

                                        222 *0.2500