A solution containing an unknown anion is treated with dilute , evolving a gas that turns acidified — Qualitative and Quantitative Analysis Chemistry Question
Question
A solution containing an unknown anion is treated with dilute $H_2SO_4$, evolving a gas that turns acidified $K_2Cr_2O_7$ paper green. Another portion of the exact same solution gives a deep violet coloration when treated with alkaline sodium nitroprusside. The anions sequentially identified are:
Answer: B
💡 Solution & Explanation
The gas that turns dichromate green is $SO_2$, indicating a sulphite ($SO_3^{2-}$). The deep violet complex formed with sodium nitroprusside ($Na_4[Fe(CN)_5NOS]$) specifically confirms the presence of a sulphide ($S^{2-}$).
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