The digestion of a 0.1417-g sample of a phosphorus-containing compound in amixture of HNO3...

The digestion of a 0.1417-g sample of a phosphorus-containing compound in a

mixture of HNO3 and H2SO4 resulted in the formation of CO2, H2O, and H3PO4. Addition of ammonium

molybdate yielded a solid having the composition (NH4)3PO4 -12MoO3 (1876.3 g/mol). This precipitate

was filtered, washed, and dissolved in 50.00 mL of 0.2000 M NaOH:

(NH4)3PO4 . 12MoO3(s) + 26OH- → HPO42- 12MoO42- + 14H2O + 3NH3(g)

After the solution was boiled to remove the NH3, the excess NaOH was titrated with 14.17 mL of 0.1741

M HCl to a phenolphthalein end point. Calculate the percentage of phosphorus in the

sample.