NiCl₂ (Nickel Chloride) Salt Analysis – CBSE Class 12
1. Preliminary Examination
- Appearance: Green crystalline solid, soluble in water.
- Flame Test: No characteristic flame color (nickel salts usually do not give flame color).
2. Dry Heating Test
- Observation: On strong heating, may decompose with no characteristic odor or residue.
3. Group Analysis
Nickel Ion (Ni²⁺) belongs to Group IV: Zinc Group (Ammoniacal Sulphide Group).
- Group Reagent: H₂S gas in ammoniacal medium (NH₄Cl + NH₄OH).
- Purpose: Selective precipitation of metal sulphides in ammoniacal medium to separate Ni²⁺ along with Zn²⁺, Co²⁺, and Mn²⁺ from other groups.
- Group Precipitate: Sulphides of Ni²⁺, Zn²⁺, Co²⁺, Mn²⁺ (usually white to colored ppt.).
- Observation: A greenish or light-colored sulphide precipitate forms in this group, indicating the presence of Ni²⁺.
4. Confirmatory Tests for Ni²⁺ (Nickel Ion)
| Test | Procedure | Observation | Inference | Chemical Reaction |
|---|---|---|---|---|
| Ammonium Hydroxide (NH₄OH) | Add NH₄OH dropwise to salt solution. | Green ppt. of Ni(OH)₂ initially, dissolves in excess NH₄OH to form a blue solution of [Ni(NH₃)₆]²⁺ | Ni²⁺ confirmed | NiCl₂ + 2NH₄OH → Ni(OH)₂↓ (green) + 2NH₄Cl Ni(OH)₂ + 6NH₄OH → [Ni(NH₃)₆]Cl₂ (blue solution) + 2H₂O |
| Sodium Carbonate (Na₂CO₃) | Add sodium carbonate solution to salt solution. | Light green ppt. of NiCO₃ | Ni²⁺ confirmed | NiCl₂ + Na₂CO₃ → NiCO₃↓ (light green) + 2NaCl |
| Potassium Ferrocyanide (K₄[Fe(CN)₆]) | Add K₄[Fe(CN)₆] to salt solution. | Light greenish ppt. (insoluble complex) | Ni²⁺ confirmed | Ni²⁺ + K₄[Fe(CN)₆] → Ni₂[Fe(CN)₆]↓ (light green ppt.) |
5. Test for Anion (Cl⁻: Chloride)
| Test | Procedure | Observation | Inference | Chemical Reaction |
|---|---|---|---|---|
| Silver Nitrate (AgNO₃) | Add AgNO₃ to acidified salt solution. | White curdy ppt. of AgCl, soluble in NH₄OH. | Cl⁻ confirmed | NiCl₂ + 2AgNO₃ → 2AgCl↓ (white) + Ni(NO₃)₂ |
6. Summary of Identification
- Group: IV (Zinc Group – Ammoniacal Sulphide Group)
- Cation: Ni²⁺ (Nickel)
- Anion: Cl⁻ (Chloride)
- Salt: NiCl₂ (Nickel Chloride)
7. Important Notes
- Ni(OH)₂ green ppt dissolves in excess ammonium hydroxide to form a blue ammine complex.
- Anion Cl⁻ confirmed by white precipitate of AgCl which dissolves in NH₄OH.
- Group separation helps to separate Ni from other metals before confirmatory tests for accurate identification.