In qualitative test for identification of presence of phosphorus, the compound is heated with an oxidising agent. Which is further treated with nitric acid and ammonium molybdate respectively. The yellow coloured precipitate obtained is :
- Na3PO4 12MoO3
- (NH4)3PO4 12(NH4)2MoO4
- MoPO4 21NH4NO3
- (NH4)3PO4 12MoO3
Answer
(4) (NH4)3PO4 12MoO3
Solution
The oxidising agent (Na2O2) converts P into phosphate, which nitric acid turns into H3PO4:
Na3PO4 + 3HNO3 H3PO4 + 3NaNO3
H3PO4 + 12(NH4)2MoO4 + 21HNO3
(NH4)3PO4 12MoO3 + 21NH4NO3 + 12H2O
The canary-yellow precipitate is ammonium phosphomolybdate, (NH4)3PO4 12MoO3.
Answer: (4)