JEE Main · 2021 · 27 Jul 2021 · Shift 2 · Practical and Analytical Chemistry

Fusion with sodium metal converts the covalently held elements of an organic compound into soluble sodium salts: nitrogen appears as $\mathrm{NaCN}$, sulphur as $\mathrm{N}{\mathrm{a}}_2\mathrm{S}$, halogen as $\mathrm{NaX}$, and phosphorus as $\mathrm{N}{\mathrm{a}}_3\mathrm{P}$, which is oxidised to phosphate before testing. Each of these ions is then identified by its own test on the aqueous extract. Carbon and oxygen give no such ionic species in the fusion, so the set detected is sulphur, nitrogen, phosphorus and halogens.