Purification and Characterisation of Organic Compounds
- Which one of the following reactions does NOT belong to "Lassaigne's test"? Answer: 4. mathrm2CuO + C xrightarrowΔ 2Cu + CO₂ Key idea: Lassaigne's test fuses the organic compound with sodium to convert N, S and halog... 1
- Match List I with List IIList I (Mixture): A. CHCl_3 + C_6H_5NH_2 B. Crude oil in petroleum industry C. Glycerol from spent-lye D. Aniline - waterList II (Method of Separation): I. Distillation under reduced pressure II. Steam distillation III. Fract… Answer: 1. A-IV, B-III, C-I, D-II CHCl₃ + aniline: boiling points well apart (334 K vs 457 K), simple distillation (IV). Crude oil: fraction... 1
- On heating, some solid substances change from solid to vapour state without passing through liquid state. The technique used for the purification of such solid substances based on the above principle is known as Answer: 3. Sublimation Key idea: sublimation is the conversion of solid directly into vapour. Solids like camphor, naphthalene and iodine ar... 1
- In Lassaigne's extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with Fe^3+ due to the formation of - Answer: 1. [Fe(SCN)]²⁺ Key idea: When N and S are both present, Na fusion forms sodium thiocyanate, NaSCN, in the Lassaigne's extract. Na +... 1
- The Kjeldahl's method for the estimation of nitrogen can be used to estimate the amount of nitrogen in which one of the following compounds ? Answer: 4. [structure in figure] Key idea: Kjeldahl's method converts N to (NH₄)₂SO₄ on digestion; it fails for N in nitro, azo groups and i... 1
- An organic compound contains 78% (by wt.) carbon and remaining percentage of hydrogen. The right option for the empirical formula of this compound is : [Atomic wt. of C is 12, H is 1] Answer: 3. CH₃ Key idea: divide percentage by atomic mass, then take the simplest ratio. C: 78/12=6.5 ; H: 22/1=22 . Ratio H : C = 22/6.5≈3.... 1
- Paper chromatography is an example of : Answer: 2. Partition chromatography In paper chromatography the stationary phase is water held in the cellulose fibres of the paper, and the... 1
- The most suitable method of separation of 1 : 1 mixture of ortho and para-nitrophenols is : Answer: 3. Steam distillation Key idea: o-nitrophenol is steam volatile, p-nitrophenol is not. o-Nitrophenol has intramolecular hydrogen bon... 1