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In the confirmatory test for phosphate ions, a canary yellow precipitate is formed. What is the correct chemical formula of this precipitate?

1. (NH4)3PO4 * 12MoO3
2. (NH4)2MoO4
3. (NH4)3PO4 * 12MoO3 * xH2O
4. MoS2

Correct answer: (NH4)3PO4 * 12MoO3

Solution

When a phosphate solution is treated with ammonium molybdate in excess nitric acid and warmed, a characteristic canary yellow precipitate of ammonium phosphomolybdate, (NH4)3PO4 * 12MoO3, is formed, confirming the presence of phosphate ions.

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