Free NEET Chemistry multiple-choice questions on Organic Analysis. Attempt each question and reveal the answer with a full explanation.
The 'Beilstein test' is used for the detection of: Halogens Nitrogen Sulfur Oxygen The Azo-dye test is used for the detection of which functional group? Primary aromatic amines Secondary aliphatic amines Aliphatic amides Tertiary amines The presence of a CH 3CO- (acetyl) group or CH 3CH(OH)- group can be detected by: Iodoform test Fehling's test Tollen's test Molisch test In the chromatography process, if the distance moved by the solvent is 10 cm and the distance moved by the compound is 6 cm , the R f value is: 0.6 1.67 0.4 60 In the 'Biuret Test', a violet-purple color is observed when a compound containing at least two peptide bonds is treated with: Alkaline CuSO 4 solution Acidic FeCl 3 solution NaNO 2 and HCl Benedict's solution Which of the following elements is estimated by the 'Carius Method'? Halogens Nitrogen Carbon Hydrogen Fehling's solution B, used in the detection of reducing sugars, consists of an alkaline solution of: Sodium potassium tartrate Sodium citrate Potassium oxalate Sodium acetate When an ammonium salt is heated with NaOH solution, a gas is evolved which turns red litmus blue and gives dense white fumes with a glass rod dipped in HCl . The gas is: NH 3 N 2 NO 2 H 2 The presence of an -OH group in a phenol can be detected using which reagent? Neutral FeCl 3 solution Tollen's reagent Sodium bicarbonate Schiff's reagent Aniline reacts with bromine water to give a white precipitate. The product formed is: 2,4,6-Tribromoaniline 2,4-Dibromoaniline p-Bromoaniline o-Bromoaniline The evolution of CO 2 gas with brisk effervescence when an organic compound is treated with sodium bicarbonate ( NaHCO 3 ) indicates the presence of: Carboxylic acid group ( -COOH ) Phenolic group ( -OH ) Alcoholic group ( -OH ) Aldehydic group ( -CHO ) A mixture of two organic compounds can be separated by chromatography based on their different: Retardation factors ( R f ) Boiling points Solubilities in water Adsorption on filter paper The presence of an impurity in an organic solid generally causes its melting point to: Decrease and become less sharp (broaden) Increase and become more sharp Remain unchanged Increase and become less sharp Which of the following organic compounds will reduce Tollen's reagent to give a silver mirror? Glucose Sucrose Acetone Benzophenone The process of 'Sublimation' is used for the purification of which of the following substances? Iodine Sodium Chloride Urea Glucose In the chromatography of a mixture, a compound 'A' moves 4 cm and compound 'B' moves 8 cm while the solvent front moves 10 cm . The R f values for A and B are respectively: 0.4 and 0.8 0.8 and 0.4 2.5 and 1.25 4.0 and 8.0 Baeyer's reagent is used to detect unsaturation in organic compounds. Chemically, Baeyer's reagent is: Alkaline KMnO 4 Acidified KMnO 4 Neutral FeCl 3 Ammoniacal AgNO 3 A pure organic solid is characterized by a sharp melting point. If a small amount of an impurity is mixed with the solid, the melting point will generally: Decrease and become a range Increase and stay sharp Increase and become a range Remain unchanged The presence of sulfur in an organic compound is confirmed by the sodium nitroprusside test. The appearance of which color indicates sulfur? Violet Prussian blue Blood red Yellow A salt produces a pungent smell of vinegar when treated with concentrated H 2SO 4 . On adding neutral FeCl 3 to its aqueous extract, a deep red color is obtained. The anion is: Acetate ( CH 3COO - ) Formate ( HCOO - ) Oxalate ( C 2O 4 2- ) Nitrate ( NO 3 - ) Which chromatography technique is most suitable for separating the components of a mixture of pigments from green leaves? Paper chromatography Gas chromatography Distillation Sublimation In the Dumas method, the nitrogen oxides formed during combustion are reduced to free nitrogen by passing the gas over: Heated copper gauze Heated copper oxide Potassium hydroxide Calcium chloride The appearance of a purple/violet color when an organic compound is heated with Ninhydrin reagent indicates the presence of: -Amino acids Phenols Aldehydes Alcohols The R f value in paper chromatography is defined as the ratio of the distance moved by the substance to the distance moved by the solvent. Which of the following is true about R f values? It is always less than or equal to 1. It can be greater than 1. It depends only on the distance moved by the solvent. It is independent of the nature of the solvent. The reagent used to distinguish between aldehydes and ketones is: Tollen's reagent Br 2 water FeCl 3 Lucas reagent In the test for the acetate ion ( CH 3COO - ), the salt is heated with concentrated H 2SO 4 and ethanol. The characteristic smell observed is due to the formation of: Ethyl acetate Acetic acid Acetaldehyde Diethyl ether In the estimation of phosphorus by the Carius method, the organic compound is heated with fuming HNO 3 . What is the purpose of fuming HNO 3 ? To oxidize phosphorus to phosphoric acid To reduce phosphorus to phosphine To precipitate phosphorus as Ag 3PO 4 To dehydrate the organic compound In chromatography, the term hR f is often used to avoid decimals. It is mathematically expressed as: R f 100 R f / 100 1 / R f R f 10 A carboxylic acid can be identified by its reaction with PCl 5 , which results in the evolution of fumes that turn a glass rod dipped in NH 4OH solution white. These fumes are of: HCl POCl 3 Cl 2 COCl 2 Which of the following is known as Brady's reagent and is used to detect the carbonyl group? 2,4-Dinitrophenylhydrazine Phenylhydrazine Hydroxylamine Semicarbazide 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 Fe4[Fe(CN)6]3.xH2O NaSCN [Fe(CN)5NOS] 4- [Fe(SCN)] 2+ Fehling’s solution ‘A’ is aqueous copper sulphate alkaline copper sulphate alkaline solution of sodium potassium tartrate (Rochelle’s salt) aqueous sodium citrate Which one of the following reactions does NOT belong to “Lassaigne’s test” ? 2CuO + C ->[ ] 2Cu + CO2 Na + C + N ->[ ] NaCN 2Na + S ->[ ] Na2S Na + X ->[ ] NaX The separation of a mixture of o -nitrophenol and p -nitrophenol can be efficiently achieved by which of the following techniques? Steam distillation Fractional distillation Sublimation Crystallization During Lassaigne’s test, the elements present in an organic compound are converted from : Ionic form to ionic form Covalent form to ionic form Ionic form to covalent form Covalent form to covalent form Which functional group gives a positive result with the Carbylamine test? Primary amine Secondary amine Tertiary amine Amide In the Lucas test, an alcohol reacts immediately with Lucas reagent ( ZnCl 2 + conc. HCl ) to produce turbidity. The alcohol is: Tertiary Secondary Primary Methanol Which of the following compounds will give a positive iodoform test? CH 3CH(OH)CH 3 CH 3CH 2CH 2OH C 6H 5CHO CH 3OCH 3 The Kjeldahl's method for the estimation of nitrogen cannot be applied to which of the following organic compounds? Nitrobenzene Aniline Benzylamine Acetamide Which color is produced by a secondary alcohol in the Victor Meyer's test? Blue Blood red Colorless Green When a secondary amine is treated with Hinsberg's reagent (benzene sulfonyl chloride), the resulting product is: Insoluble in alkali Soluble in alkali A liquid which cannot be isolated Does not form a precipitate The active oxidizing species in Tollen's reagent is: [Ag(NH 3) 2] + Ag + Ag 2O [Ag(NH 3) 4] + Schiff's reagent is a solution of: Rosaniline hydrochloride decolorized by SO 2 Resorcinol in HCl Magnesium mixture Ammoniacal silver nitrate Which of the following reagents is used in Molisch's test to detect the presence of carbohydrates? -naphthol in ethanol Resorcinol in HCl Benedict's solution Iodine in KI The presence of a phenolic group in an organic compound can be confirmed by the formation of a violet coloration with which reagent? Neutral FeCl 3 Acidic FeCl 3 Alkaline KMnO 4 Ammoniacal AgNO 3 Terminal alkynes like ethyne react with ammoniacal silver nitrate to form a precipitate of which color? White Yellow Red Black In Liebig's method for the estimation of carbon and hydrogen, the CO 2 produced is absorbed in a bulb containing: Potassium hydroxide solution Anhydrous calcium chloride Concentrated sulfuric acid Soda lime In the Carius method for the estimation of halogens, 250 mg of an organic compound gave 141 mg of AgBr . The percentage of bromine in the compound is: (Atomic mass Ag=108, Br=80 ) 24% 48% 12% 60% In the Victor Meyer's test, what is the color observed for a primary alcohol after adding NaOH ? Blood red Blue Colorless Yellow In the Dumas method, the volume of nitrogen gas collected is measured at room temperature and pressure. The purpose of using a 50% KOH solution in the nitrometer is: To absorb CO 2 and H 2O vapor To catalyze the decomposition of NO x To act as a lubricant for the piston To maintain a constant temperature During the estimation of carbon in an organic compound by Liebig's method, 0.24 g of the compound gave 0.66 g of CO 2 . The percentage of carbon in the compound is: 75% 50% 25% 33.3% An organic salt solution turns deep red upon the addition of neutral FeCl 3 solution. On boiling, a reddish-brown precipitate is formed. The anion is: CH 3COO - C 2O 4 2- Cl - NO 3 - Zeisel's method is used for the estimation of which functional group in an organic compound? Methoxy group ( -OCH 3 ) Carboxyl group ( -COOH ) Amino group ( -NH 2 ) Hydroxyl group ( -OH ) The technique of Thin Layer Chromatography (TLC) is used for the separation of amino acids. Which of the following is true regarding TLC? It is a type of adsorption chromatography The stationary phase is a liquid It is a type of partition chromatography only It requires a very large amount of sample In the Victor Meyer's test, which of the following alcohols does not produce any color (remains colorless) after the final addition of NaOH ? Tertiary alcohol Primary alcohol Secondary alcohol All alcohols produce color In the chromatography experiment, the R f value is mathematically defined as: Distance traveled by the substance / Distance traveled by the solvent Distance traveled by the solvent / Distance traveled by the substance Initial mass of substance / Final mass of substance Rate of flow of substance / Rate of flow of air In the estimation of Nitrogen by Dumas method, the organic compound is heated with which substance in an atmosphere of CO 2 ? CuO Na 2O 2 H 2SO 4 CaO The Xanthoproteic test is used to detect proteins containing aromatic amino acids. Upon heating with concentrated HNO 3 , a yellow color is produced, which turns orange when treated with: Alkali ( NaOH or NH 4OH ) Alcohol Acid Water An organic compound contains 40 % carbon, 6.67 % hydrogen, and the rest is oxygen. Its empirical formula is: CH 2O CHO C 2H 4O CH 4O A compound on heating with NaOH solution evolves a gas that turns red litmus blue. When the resulting solution is acidified and treated with FeCl 3 , no characteristic color appears. The original compound could be: Urea or an Amide Aniline Phenol Nitrobenzene Which reagent can be used to distinguish between 2-pentanone and 3-pentanone? I 2/NaOH (Iodoform test) Tollen's reagent Fehling's solution Br 2/CCl 4 In the Carius method for the estimation of halogens, 0.2 g of an organic compound gave 0.188 g of AgBr . The percentage of bromine in the compound is: [Atomic mass: Ag=108, Br=80 ] 40% 20% 30% 50% In the detection of a primary aromatic amine, the compound is treated with NaNO 2 and HCl at 0-5 o C , followed by reaction with an alkaline solution of -naphthol. The observation of a brilliant orange-red dye indicates the presence of: - NH 2 group (Aromatic) - NO 2 group - CONH 2 group - NHCH 3 group Which of the following tests is used to specifically distinguish monosaccharides from disaccharides based on the rate of reaction? Barfoed's test Molisch's test Seliwanoff's test Tollen's test When proline, a cyclic amino acid, is treated with Ninhydrin reagent, the color observed is: Yellow Purple Blue Brown The role of sodium citrate in Benedict's reagent is to: Prevent the precipitation of Cu(OH) 2 by forming a soluble complex Act as a reducing agent for the sugar Provide a strongly alkaline medium Catalyze the oxidation of the aldehyde group Which gas is evolved when an organic compound containing nitrogen is heated with soda-lime ( NaOH + CaO )? Ammonia Nitrogen Nitric oxide Nitrogen dioxide In the Dumas method for the estimation of nitrogen, why is CO 2 gas passed through the combustion tube initially? To expel all the air present in the apparatus To act as a reducing agent for nitrogen oxides To provide an oxygen source for combustion To maintain a high temperature in the furnace The blood-red coloration produced when FeCl 3 is added to a solution of potassium thiocyanate ( KSCN ) is due to the formation of: [Fe(SCN)(H 2O) 5] 2+ [Fe(CN) 6] 3- Fe(OH) 3 [Fe(H 2O) 6] 3+ In column chromatography, if a mixture of Benzene (non-polar) and Benzoic acid (polar) is eluted using a non-polar solvent on a silica gel column, which compound will elute first? Benzene Benzoic acid Both will elute together Neither will elute Kjeldahl's method fails for which of the following compounds because the nitrogen does not convert to (NH 4) 2SO 4 upon digestion with H 2SO 4 ? Pyridine Acetamide Aniline Glycine Which of the following organic compounds can be estimated by the Kjeldahl method for nitrogen content? Aniline Nitrobenzene Azobenzene Pyridine During the Carius method for the estimation of chlorine, 0.25 g of an organic compound gave 0.40 g of silver chloride. What is the approximate percentage of chlorine in the compound? (Atomic mass of Ag = 108, Cl = 35.5 ) 39.58 % 25.00 % 48.20 % 15.45 % Which of the following reagents is used to distinguish between Ethanol and Methanol? I 2 and NaOH (Iodoform test) Sodium metal Lucas reagent Phosphorus pentachloride Lassaigne's test for the detection of nitrogen fails for which of the following compounds? NH 2NH 2 (Hydrazine) C 6H 5NH 2 (Aniline) CH 3CONH 2 (Acetamide) H 2NCONH 2 (Urea) The 'Beilstein test' for halogens in an organic compound is based on the formation of: Volatile cupric halides Insoluble silver halides Gaseous hydrogen halides Prussian blue complexes A mixture of naphthalene and benzoic acid can be separated by using which of the following reagents followed by filtration? Aqueous NaHCO 3 Cold water Ether Benzene Which of the following compounds gives a white precipitate with Br 2 water? Phenol Ethanol Benzene Acetic acid Which of the following organic compounds will give a positive result with Tollen's reagent but a negative result with Fehling's solution? Benzaldehyde Acetaldehyde Glucose Formaldehyde In the chromatography of a mixture of three dyes, the R f values are 0.2, 0.5, and 0.8. Which dye has the maximum affinity for the stationary phase? The dye with R f = 0.2 The dye with R f = 0.5 The dye with R f = 0.8 All have equal affinity Which of the following tests is used to identify primary amines by the characteristic pungent smell of an isothiocyanate? Hoffmann's mustard oil test Libermann's nitroso test Carbylamine test Gattermann reaction In Zeisel's method for the estimation of methoxy groups, the organic compound is heated with concentrated HI to produce: CH 3I CH 3OH CH 4 CH 3I and CH 3OH Lassaigne's test for nitrogen fails in the case of hydrazine ( NH 2NH 2 ) because: It does not contain carbon It is a gas It reacts with sodium to form NaN 3 It is highly explosive Barfoed's test is used to distinguish between: Monosaccharides and Disaccharides Aldoses and Ketoses Reducing and Non-reducing sugars Pentoses and Hexoses 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? Which test is used to distinguish between primary, secondary, and tertiary nitroalkanes? Victor Meyer's test Lucas test Mulliken-Barker test Liebermann's nitroso test In the Carius method for the estimation of halogens, 0.15 g of an organic compound gave 0.12 g of AgBr . The percentage of bromine in the compound is: [Atomic mass: Ag=108, Br=80 ] 34.04% 42.12% 25.55% 15.20% In the Mulliken-Barker test for the nitro group, the nitro compound is reduced to hydroxylamine using Zn/NH 4Cl and then treated with Tollen's reagent to give: A silver mirror A red dye A blue solution A yellow precipitate In the detection of carbon and hydrogen, the organic compound is heated with dry CuO . The CO 2 produced is passed through lime water. If hydrogen is present, it is converted to H 2O , which is detected using: Anhydrous CuSO 4 Anhydrous CaCl 2 Anhydrous Na 2SO 4 Fused KOH In Libermann's nitroso test for phenols, a characteristic sequence of colors is observed. The correct sequence after adding concentrated H 2SO 4 , NaNO 2 , and finally NaOH is: Red Blue Blue Red Yellow Green Colorless Pink Which of the following tests is specific for identifying a ketose sugar like fructose from an aldose sugar like glucose? Seliwanoff's test Benedict's test Fehling's test Tollen's test Seliwanoff's test is a biochemical test used to distinguish between: Aldoses and Ketoses Monosaccharides and Disaccharides Reducing and Non-reducing sugars Glucose and Galactose The Stepanow method is used for the estimation of which of the following in organic compounds? Halogens Nitrogen Sulfur Phosphorus Which of the following organic compounds will produce a wine-red color with neutral FeCl 3 solution due to the presence of an enolic group? Acetylacetone Acetaldehyde Acetone Ethyl acetate Which of the following tests produces a white precipitate when an aliphatic amide is heated with NaOH solution and the evolved gas is passed through mercuric chloride solution? Amide hydrolysis test Ninhydrin test Biuret test Carbylamine test The stability of the red-colored Nickel-Dimethylglyoxime complex is enhanced by which type of interaction within the molecule? Intramolecular hydrogen bonding Intermolecular hydrogen bonding Ionic bonding Van der Waals forces