Free NEET Chemistry multiple-choice questions on Salt Analysis: Anions. Attempt each question and reveal the answer with a full explanation.
The brown ring test for nitrates is due to the formation of the complex: [Fe(H 2O) 5(NO)] 2+ [Fe(H 2O) 4(NO) 2] 2+ [Fe(H 2O) 5(NO)] 3+ [Fe(H 2O) 4(NO) 2] 3+ Which gas is evolved when a carbonate salt reacts with dilute HCl ? CO 2 CO SO 2 H 2 A student added sodium nitroprusside to an alkaline extract of an organic compound and observed a purple color. This indicates the presence of: Sulfur Nitrogen Chlorine Oxygen In a test tube containing a salt, a few drops of dilute H2SO4 was added, which gave colourless vapours having the smell of vinegar. The vapours turned the blue litmus paper red. Identify the correct anion from the following : Carbonate, CO3 2- Sulphide, S 2- Acetate, CH3COO- Sulphate, SO4 2- When a mixture containing chloride ions is heated with concentrated H 2SO 4 and solid K 2Cr 2O 7 , deep red vapors are evolved. These vapors, when passed into NaOH solution, turn it yellow. The yellow color is due to the formation of: Na 2CrO 4 CrO 2Cl 2 CrO 3 Na 2Cr 2O 7 Magnesia mixture used for the detection of phosphate ions consists of MgCl 2 , NH 4OH , and: NH 4Cl NaCl KCl BaCl 2 In the detection of oxalate ions, the white precipitate of calcium oxalate ( CaC 2O 4 ) is soluble in: Dilute HCl Dilute CH 3COOH Ammonium hydroxide Cold water In the systematic analysis of anions, the addition of AgNO 3 to a solution gives a yellow precipitate that is completely insoluble in NH 4OH . The anion is: I - Br - Cl - PO 4 3- Which reagent is used to distinguish between nitrite ( NO 2 - ) and nitrate ( NO 3 - ) ions in dilute acid medium? Dilute H 2SO 4 (Nitrite gives NO 2 gas) Concentrated H 2SO 4 only Aqueous NaOH only Potassium dichromate solution In the Layer Test for Bromides and Iodides, chlorine water is added to the salt solution in the presence of CHCl 3 or CS 2 . The appearance of an orange-brown layer indicates: Bromine ( Br 2 ) Iodine ( I 2 ) Chlorine ( Cl 2 ) Nitrogen dioxide ( NO 2 ) The reagent used for the detection of Carbonate ( CO 3 2- ) in the presence of Bicarbonate ( HCO 3 - ) is: Dilute MgSO 4 (in cold) Boiling MgSO 4 Dilute BaCl 2 Silver nitrate A student added BaCl 2 solution to an unknown salt solution and obtained a white precipitate that was insoluble in concentrated HCl . The anion present is: SO 4 2- CO 3 2- SO 3 2- S 2- In the Carius method for the estimation of bromine, the percentage of bromine is calculated using the formula: 80 188 Mass of AgBr Mass of compound 100 188 80 Mass of AgBr Mass of compound 100 35.5 143.5 Mass of AgCl Mass of compound 100 80 108 Mass of AgBr Mass of compound 100 Paper chromatography is primarily based on the principle of: Partition Adsorption Ion exchange Capillary action only In the systematic analysis of anions, which of the following reagents can be used to distinguish between SO 3 2- and CO 3 2- ions by observing the effect on acidified potassium dichromate paper? Sulfur dioxide gas evolved from SO 3 2- turns the paper green, while CO 2 has no effect. Carbon dioxide gas evolved from CO 3 2- turns the paper green, while SO 2 has no effect. Both gases turn the paper green. Both gases turn the paper yellow. In the detection of the fluoride ion ( F - ), the salt is heated with concentrated H 2SO 4 in a glass test tube. A 'greasy' appearance and the 'etching of glass' is observed due to the formation of: SiF 4 HF H 2SiF 6 CaF 2 The formula of the 'Yellow Precipitate' formed in the test for phosphate ions using ammonium molybdate and concentrated HNO 3 is: (NH 4) 3[P(Mo 12 O 40 )] (NH 4) 2MoO 4 Mg(NH 4)PO 4 AlPO 4 Which of the following is an example of an adsorption indicator used in the titration of Cl - with AgNO 3 (Fajans' method)? Fluorescein Phenolphthalein Methyl red Starch In the Carius method for the estimation of iodine, 0.20 g of an organic compound gave 0.235 g of AgI . The percentage of iodine in the compound is: (Atomic mass: Ag=108, I=127 ) 63.5 % 54.0 % 48.2 % 72.1 % The 'Etching of Glass' test for the fluoride ion ( F - ) depends on the formation of which volatile compound? SiF 4 HF H 2SiF 6 CaF 2 Preparation of Na 2CO 3 extract (Soda extract) for anion analysis is necessary to: Remove interfering cations by precipitating them as carbonates Increase the concentration of the anions Neutralize the acid present in the salt Make the solution basic for better detection On adding BaCl 2 solution to a salt solution, a white precipitate is formed which is soluble in dilute HCl with the evolution of a gas. The anion is: SO 3 2- SO 4 2- PO 4 3- Cl - In the estimation of sulfur by the Carius method, sulfur is precipitated as: BaSO 4 PbSO 4 Ag 2S Na 2SO 4 In the systematic analysis of anions, a salt solution when treated with AgNO 3 gives a yellow precipitate which is partially soluble in NH 4OH . The anion present is: Br - I - Cl - PO 4 3- In the estimation of nitrogen using the Dumas method, the volume of nitrogen collected was 22.4 ,mL at STP. If the mass of the organic compound taken was 0.28 ,g , the percentage of nitrogen is: 10.0 % 5.0 % 20.0 % 14.0 % In the detection of borate radical ( BO 3 3- ), the salt is heated with concentrated H 2SO 4 and ethyl alcohol. The evolved vapors burn with a green-edged flame due to the formation of: Ethyl borate Boric anhydride Diethyl ether Ethyl sulfate Which of the following reagents can distinguish between carbonate ( CO 3 2- ) and bicarbonate ( HCO 3 - ) in aqueous solution at room temperature? MgSO 4 BaCl 2 Dilute HCl CaCl 2 When silver nitrate solution is added to a neutral solution of an arsenite ( AsO 3 3- ), a precipitate of which color is formed? Yellow Reddish-brown White Black In the gravimetric estimation of phosphorus, the final substance weighed is Magnesium pyrophosphate. Its chemical formula is: Mg 2P 2O 7 Mg(NH 4)PO 4 Mg 3(PO 4) 2 MgP 2O 6 When CuSO 4 solution is added to an aqueous solution of KI , a white precipitate and a brown solution are formed. The brown color can be removed by adding: Na 2S 2O 3 HCl KNO 3 NaOH In the test for phosphorus in an organic compound, the compound is heated with an oxidizing agent like Na 2O 2 . The phosphorus is converted into phosphate, which is then identified using: Ammonium molybdate and HNO 3 Magnesia mixture Silver nitrate Barium chloride Which of the following tests can distinguish between sulfite ( SO 3 2- ) and carbonate ( CO 3 2- ) ions? Passing the evolved gas through acidified K 2Cr 2O 7 paper Passing the evolved gas through lime water Adding dilute HCl and observing the gas Adding BaCl 2 solution When silver nitrate ( AgNO 3 ) is added to a solution of sodium thiosulfate ( Na 2S 2O 3 ), a white precipitate is formed which slowly turns yellow, then brown, and finally black. The final black precipitate is: Ag 2S Ag 2S 2O 3 Ag 2O Ag Iodide ions ( I - ) can be detected by the addition of starch solution in the presence of an oxidizing agent. The appearance of which color indicates the presence of Iodine? Deep blue Red Green Yellow In the identification of the nitrate ion ( NO 3 - ) in the presence of the nitrite ion ( NO 2 - ), the nitrite must be removed first. Which reagent is commonly used for this purpose? Urea and dilute H 2SO 4 Concentrated HNO 3 Sodium hydroxide Potassium permanganate In the qualitative analysis of Group III, if phosphate ions are present, they must be removed before proceeding to Group IV. This is typically done using the 'Zirconyl Chloride' method or the 'Ferric Chloride' method because: Phosphates of Group IV and V might precipitate prematurely in Group III Phosphates interfere with the solubility of H 2S gas Phosphates reduce the concentration of NH 4OH Phosphates act as buffers and prevent pH changes Which of the following anions interferes with the 'Brown Ring' test for the nitrate ion? Br - SO 4 2- CO 3 2- PO 4 3- In the Carius method for the estimation of sulfur, 0.468 ,g of an organic compound gave 0.668 ,g of barium sulfate. The percentage of sulfur in the compound is: [Atomic mass: Ba=137, S=32, O=16 ] 19.60 % 32.10 % 13.72 % 25.40 % Lime water turns milky when CO 2 is passed through it, but the milkiness disappears on passing excess CO 2 . This disappearance is due to the formation of: Ca(HCO 3) 2 CaCO 3 CaO Ca(OH) 2 Phosphate ions ( PO 4 3- ) are detected by heating the salt with concentrated HNO 3 and which reagent to give a 'Canary Yellow' precipitate? Ammonium molybdate Potassium ferrocyanide Silver nitrate Barium chloride In the detection of the nitrate ion ( NO 3 - ), when the salt is heated with concentrated H 2SO 4 and copper turnings, the evolution of brown fumes is due to the formation of: NO 2 NO N 2O N 2O 5 Which of the following ions produces a white precipitate with AgNO 3 that is soluble in NH 4OH ? Cl - Br - I - PO 4 3- The reagent used in the 'Brown Ring Test' for the detection of nitrates must be freshly prepared because: FeSO 4 is easily oxidized by air to Fe 2(SO 4) 3 FeSO 4 reacts with H 2SO 4 to form a gas The brown complex is unstable at room temperature Freshly prepared FeSO 4 contains Fe 3+ ions