A) Sulphur
B) Nitrogen
C) Fluorine
D) Phosphorus
Correct Answer: D
Solution :
The phosphorus containing organic compound are detected by 'Lassaigne's test' by heated with an oxidizing agent (sodium peroxide) The phosphorus present in the compound in oxidised to phosphate. The solution is boiled with nitric acid and then treated with ammonium molybdate to produced canary yellow precipitate. \[\underset{\left( Ammonium\text{ }molybdate \right)}{\mathop{\begin{matrix} N{{a}_{3}}P{{O}_{4}}+3HN{{O}_{3}}\to {{H}_{3}}P{{O}_{4}}+3NaN{{O}_{3}} \\ {{H}_{3}}P{{O}_{4}}+12{{(N{{H}_{4}})}_{2}}Mo{{O}_{4}}+21HN{{O}_{3}}\to \\ \end{matrix}}}\,\] \[{{(N{{H}_{4}})}_{3}}P{{O}_{4}}.12Mo{{O}_{3}}\downarrow +21N{{H}_{4}}N{{O}_{3}}+12{{H}_{2}}O\] (Ammonium phosphomolybdate) (canary yellow precipitate)You need to login to perform this action.
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