Question

How will you distinguish between the following pairs of compounds:

1.Zinc nitrate solution and Calcium nitrate solution.

1. Sodium nitrate solution and sodium chloride solution.

2. Iron (III) chloride solution and Copper Chloride solution.

3. Iron (II) sulphate solution and copper (II) sulphate solution.

4. Zinc nitrate solution and calcium nitrate solution.

5. Iron (II) chloride and Iron (III) chloride solution.

Answer 1

1. Add NaOH solution in excess to the two solutions. The one in which white ppt. initially formed dissolves in excess of NaOH solution is Zn(NO3)2 solution and the other is Ca(NO3)2 solution.

2. Add freshly prepared ferrous sulphate solution to the two solutions. Then by the side of the test tube, pour cone, sulphuric acid to each slowly. The one in which brown ring appears is sodium nitrate solution while the other is sodium chloride solution.

3. Add NaOH solution to both the solutions. The one which gives a reddish brown ppt. is iron(III) chloride solution and the one which gives blue ppt. is copper chloride solution.

4. When sodium hydroxide solution is added to iron (II) sulphate solution, a ***** green precipitate is formed. When sodium hydroxide solution is added to copper (II) sulphate solution, light blue precipitate is formed.

5. When ammonium hydroxide is added to zinc nitrate solution, a white precipitate is formed. The white precipitate dissolves when excess of ammonium hydroxide is added. When ammonium hydroxide is added to calcium nitrate solution, no visible reaction occurs even with the addition of excess of NH4OH.

6. When sodium hydroxide is added to Iron (II) chloride, ***** green precipitate of Fe(OH)2 is formed.

FeCl2 + 2NaOH ⟶ Fe (OH)2 ↓ + 2NaCl

When sodium hydroxide is added to iron (III) chloride, reddish brown precipitate is formed

FeCl3 + 2NaOH ⟶ Fe(OH)3 + 3NaCl