ChemistryHardHigh School (11–12)Organic Chemistry: Some Basic Principles and Techniques › Purification and Analysis of Organic CompoundsNEET
Created by StemPy LabA student separates a mixture by column chromatography and checks the fractions by thin layer chromatography. Two statements about these methods are given below. Statement I: In column chromatography, the component that is adsorbed most strongly on the alumina or silica gel moves fastest down the column and is collected first. Statement II: Spots of colourless compounds on a thin layer plate can be seen under ultraviolet light, or by putting the plate in a covered jar with a few crystals of iodine.
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← In Kjeldahl's method, the ammonia from 0.300 g of an organic compound is passed into 25.0 mL of 0.500 mol L⁻¹ sulphuric acid. The acid left over is neutralised by 40.0 mL of 0.500 mol L⁻¹ sodium hydroxide. The compound has no nitro or azo group and no nitrogen in a ring. Take N as 14 g mol⁻¹. What is the percentage of nitrogen in the compound?The figure shows tests on a sodium fusion extract and what was seen. Read these conclusions.
(i) Tube 1 shows nitrogen; the blue colour is iron(III) hexacyanidoferrate(II).
(ii) The violet colour in Tube 4 comes from thiocyanate ions.
(iii) Tube 3 shows chlorine; bromine would give a pale yellow precipitate.
(iv) Nitric acid in Tube 3 removes cyanide and sulphide, which would also react with silver nitrate.
(v) With sulphur present, the Prussian blue shows that too little sodium was used.
How many of the statements above are correct? →
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