Match the observed colors in Lassaigne's test with their corresponding confirming ions/complexes. Wh — Practical Organic Chemistry and Purification Chemistry Question

💡 Solution & Explanation

Nitrogen forms Prussian blue ($Fe_4[Fe(CN)_6]_3$). Sulphur with sodium nitroprusside forms a deep violet complex ($Na_4[Fe(CN)_5NOS]$). If both N and S are present, $NaSCN$ forms (blood red with $Fe^{3+}$), but if fused with excess Na, $NaSCN$ decomposes into $NaCN$ and $Na_2S$, giving separate normal tests for N and S. Halogens give AgX precipitates, not a blood-red complex.