MediumChemistryHigh School (11–12)Organic Chemistry: Some Basic Principles and Techniques › Purification and Analysis of Organic CompoundsConceptualA-LevelIBNEET
Two compounds are fused with sodium, and the extract is tested…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Two compounds are fused with sodium, and the extract is tested. Compound X gives a Prussian blue colour. Nothing violet appears with sodium nitroprusside. After boiling with nitric acid, silver nitrate gives a yellow precipitate that does not dissolve in ammonia. Compound Y gives a blood red colour with iron(III) chloride, and no precipitate with silver nitrate after boiling with nitric acid. Which elements does each hold?
Need a reminder? The key ideaShow
Carbon is shown by carbon dioxide turning lime water milky, and hydrogen by water turning white copper sulphate blue. Fusion with sodium turns N, S and the halogens into CN, S and X ions. Nitrogen: Prussian blue. Sulphur: black PbS or violet with nitroprusside. Nitrogen and sulphur together: blood red . Halogens: boil with nitric acid first, then silver nitrate. Phosphorus: a yellow colour with ammonium molybdate.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Compound X. Prussian blue shows nitrogen. No violet colour means no sulphur. A yellow precipitate, insoluble in ammonia, is silver iodide. So X holds nitrogen and iodine.
Compound Y. Blood red is the thiocyanate complex, so Y holds nitrogen and sulphur. No precipitate with silver nitrate means no halogen.
Answer: X has nitrogen and iodine. Y has nitrogen and sulphur, and no halogen.
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