Salt Analysis: Copper(II) Sulphate (CuSO₄)Salt Analysis: Copper(II) Sulphate (CuSO4)
1. Physical Examination of the Salt
| Experiment | Observation | Inference |
|---|
| Colour | Blue | Cu or Ni salt may be present |
| Smell | No characteristic smell observed | Inconclusive |
| Deliquescence | Does not absorb moisture from air | Non-deliquescent |
2. Dry Heating Test
| Experiment | Observation | Inference |
|---|
| A pinch of salt is taken in a dry test tube and heated. | The color of salt turns white and suffocating smell is observed. | CuSO4 may be present |
3. Flame Test
| Experiment | Observation | Inference |
|---|
| A clean platinum wire dipped in conc. HCl is touched with the salt and held at the edge of the oxidizing flame of a Bunsen burner. | Brilliant green flame observed | Cu2+ may be present |
4. Concentrated H2SO4 Test
| Experiment | Observation | Inference |
|---|
| A pinch of salt is heated with 2 drops of conc. H2SO4. | Colourless gas with suffocating smell observed | Chloride or sulphate may be present |
5. Wet Test for Acid Radical (Sulphate Ion, SO₄²⁻)
| Experiment | Observation | Inference |
|---|
| To the aqueous solution of salt, BaCl2 solution is added. | White precipitate observed, which is insoluble in dilute HCl. | Presence of sulphate ion confirmed |
Reaction:
SO42− + BaCl2 → BaSO4↓ + 2Cl−
6. Test for Basic Radical (Copper Ion, Cu²⁺)
| Experiment | Observation | Inference |
|---|
| To salt, NaOH solution is added and warmed. | No ammoniacal smell observed. | NH4+ ion is absent |
| Add dilute HCl to aqueous solution of salt, pass H2S gas. | Black precipitate observed. | Group II elements present |
| Black ppt. is dissolved in 1:1 HNO3. Ammonium hydroxide added. | Blue solution observed | Group IIIB is present |
| Blue solution acidified with acetic acid, potassium ferrocyanide solution added. | Chocolate brown precipitate of copper ferrocyanide observed | Cu2+ ion confirmed |
Reaction:
2Cu2+ + K4Fe(CN)6 → Cu2[Fe(CN)6] (chocolate brown ppt) + 4K+
Conclusion
Acid Radical: SO42− (Sulphate ion)
Basic Radical: Cu2+ (Copper ion)