0.5 gm of an organic substance containing prosphorous was heated with sonc. `HNO_3` is the carius tube. The phosphoric acid thus formed was preciopitated with magnesia mixture `(MgNH_4PO_4)` which on ignition gave a residue of 1.0 gm of magnesium phrrophosphate `(Mg_2P_2O_7)`. The precentage of phosphorous in the organic compound is:

Options

A. `55.85%`
B. `29.72%`
C. `19.18%`
D. `20.5%`

Answer

A

Explanation

`P+HNO_3toH_2PO_4underset((NH_4Cl+MgCl_2))toMgNH_4undersetunderset(Mg_2P_2O_7)(darrtriangle)(PO_4)`
Mw of `Mg_2P_2O_7=24xx2+31xx2+16xx7=222`
percentage of `P=(62)/(222)xx("weight of "Mg_2P_2O_7)/("weight of compound")xx100`
`=(62)/(222)=(1.0)/(0.5)xx100=55.85%`