Test Q: A compound `'X'` was fused with `Na` metal and the extract gave a white precipitate with `AgNO_(3)`. The Lassaigne's extract gave a red colouration with neturl `FeCl_(3)`. Test -R while compound `'Y'` when fused with `Na` methal and subsequent analysis on its Lasaigne's extract did not give any characteristic test. Test -S while compund `Y` on fusion with fusion mixture (sodium carbonate `+` potassium nitrate) `Na_(2)O_(2),` followed by extraction, followed by addition of conc. `HNO_(3)` and ammonium molybdate give a yelow precipitate.
The formula of yellow precipitate is

Options

A. `(NH_(4))_(3)PO_(4)`
B. `MO(PO_(4))`
C. `(NH_(4))_(3)PO_(4).12MoO_(3)`
D. `Mo(PO_(4)_(2)`

Answer

C

Explanation

The formula of the yellew precipitate is `(NH_(4))_(3) PO_(4).12MoO_(3)`
`H_(3)PO_(4)+12(NH_(4))_(2)MoO_(4)+21HNO_(3)to(NH_(4))_(3)`
`PO_(4).12MoO_(3)+21NH_(4)NO_(3)+12H_(2)O`
Hence choice (c) is correct, while a,b and c are incorrect.