Systematic Analysis of Anions - Practice Questions & MCQ

Nitrite 

Take 0.1 g of salt in a test tube, add dilute sulphuric acid CO₂ gas is evolved with brisk effervescence which turns lime water milky. On passing the gas for some more time, milkiness disappears.

Take 1 mL of water extract and make it alkaline by adding ammonium hydroxide or sodium carbonate extract. Add a drop of sodium carbonate extract. Add a drop of sodium nitroprusside solution. Purple or violet colouration appears

1. Take 1 mL. of water extract or sodium carbonate extract in a test tube and add barium chloride solution. A white precipitate is formed which dissolves in dilute hydrochloric acid and sulphur dioxide gas is also evolved.
2. Take the precipitate of step (a) in a test tube and add a few drops of potassium permanganate solution acidified with dil. . Colour of potassium permanganate solution gets discharged

1. Take 1 mL. of water extract in a test tube. Add few drops of potassium iodide solution and a few drops of starch solution, acidify with acetic acid. Blue colour appears.
2. Acidify 1 mL. of water extract with acetic acid. Add 2-3 drops of sulphanilic acid solution followed by 2-3 drops of 1- naphthylamine reagent. Appearance of red colour indicates the presence of nitrite ion.

1. Take 0.1 g of salt in a China dish. Add 1 mL. of ethanol and 0.2 mL. conc. and heat. Fruity odour confirms the presence of acetate ion.
2. Take 0.1 g of salt in a test tube, add 1-2 mL distilled water, shake well, filter if necessary. Add 1 to 2 mL neutral ferric chloride solution to the filtrate. Deep red colour appears on boiling and a brown-red precipitate is formed.

A colourless gas with pungent smell, which gives dense white fumes when a rod dipped in ammonium hydroxide is brought near the mouth of the test tube.

Reddish brown gas with a pungent odour is evolved. Intensity of reddish gas increases on heating the reaction mixture after addition of solid  to the reaction mixture. Solution also acquires red colour.

Violet vapours, which turn starch paper blue and a layer of violet sublimate is formed on the sides of the tube. Fumes become dense on adding  to the reaction mixture.

Brown fumes evolve which become dense upon heating the reaction mixture after addition of copper turnings and the solution acquires blue colour.

Colourless, odourless gas is evolved which turns lime water milky and the gas coming out of lime water burns with a blue flame, if ignited

  (a) Take 0.1 g salt in a test tube. Add a pinch of manganese dioxide and 3-4 drops of conc. Sulphuric acid, Heat the reaction mixture. Greenish yellow chlorine gas is evolved which is detected by its pungent odour and bleaching action.

    (b) Take 1 ml. of sodium carbonate extract in a test tube. Acidify it with dil. or take water extract and add silver nitrate solution. A curdy white precipitate is obtained which is soluble in ammonium hydroxide solution.

    (c) Take 0.1 g salt and a pinch of solid potassium dichromate in a test tube, add conc. , heat and pass the gas evolved through sodium hydroxide solution. It becomes yellow. Divide the solution into two parts. Acidify one part with acetic acid and add lead acetate solution. A yellow precipitate is formed. Acidify the second part with dilute sulphuric acid and add 1ml of amyl alcohol followed by 1 ml of 10 % hydrogen peroxide. After gentle shaking the organic layer turns blue.

    (a) Take 0.1 g of salt and a pinch of in a test tube. Add 3-4 drops conc. sulphuric acid and heat. Intense brown fumes are evolved.

    (b) Neutralise 1 ml. of sodium carbonate extract with hydrochloric acid (or take the water extract). Add 1 ml. carbon tetrachloride  /chloroform /carbon disulphide . Now add an excess of chlorine water drop wise and shake the test tube. A brown colouration in the organic layer confirms the presence of bromide ion.

    (c) Acidify 1 ml of sodium carbonate extract with  (or take 1 mL water extract) and add silver nitrate solution. A pale yellow precipitate soluble with difficulty in ammonium hydroxide solution is obtained.

    (a) Take 1 ml. of salt solution neutralised with  and add 1 mL chloroform/carbon tetrachloride/carbon disulphide. Now add an excess of chlorine water drop wise and shake the test tube. A violet colour appears in the organic layer.

(b) Take 1ml of sodium carbonate extract acidify it with dil. (or take water extract). Add, silver nitrate solution. A yellow precipitate insoluble in  solution is obtained.

Take 1 mL of salt solution in water in a test tube. Add 2 ml of conc.  and mix thoroughly. Cool the mixture under the tap. Add freshly prepared ferrous sulphate along the sides of the test tube without shaking. A dark brown ring is formed at the junction of the two solutions.

    (a) Take 1 ml. of water extract or sodium carbonate extract acidified with acid and add calcium chloride solution. A white precipitate insoluble in ammonium oxalate and oxalic acid solution but soluble in dilute hydrochloric acid and dilute nitric acid is formed.
    (b) Take the precipitate from test (a) and dissolve it in dilute. . Add very dilute solution of and warm. Colour of solution is discharged. Pass the gas coming out through lime water. The lime water turns milky.