Title: Step-by-Step Qualitative Analysis of Nickel(II) Chloride (NiCl₂)
Introduction
Nickel(II) chloride (NiCl₂) is an inorganic compound used in electroplating, catalysts, and chemical synthesis. This document outlines the qualitative analysis of NiCl₂ to identify its cation (Ni²⁺) and anion (Cl⁻) through systematic tests.
Step-by-Step Analysis of NiCl₂
1. Preliminary Examination
| Property | Observation |
|---|---|
| Physical Appearance | Green crystalline solid (NiCl₂·6H₂O) |
| Solubility | Soluble in water, forming a green solution |
| Odor | Odorless |
2. Dry Heating Test
| Procedure | Observation | Inference | Chemical Equation |
| Heat a small sample in a dry test tube. | Green crystals turn yellow and release water vapor. | Confirms presence of hydrated NiCl₂·6H₂O. | NiCl₂·6H₂O → NiCl₂ + 6H₂O |
3. Identification of Nickel (Ni²⁺) Ion
| Test | Reagent Used | Observation | Inference | Chemical Equation |
| Ammonia (NH₃) test | Aqueous NH₃ | Blue-violet solution | Confirms Ni²⁺ presence | [Ni(H₂O)₆]²⁺ + 6NH₃ → [Ni(NH₃)₆]²⁺ + 6H₂O |
| Dimethylglyoxime (DMG) test | DMG reagent + NH₃ | Red precipitate | Confirms Ni²⁺ presence | Ni²⁺ + 2C₄H₈N₂O₂ → Ni(C₄H₈N₂O₂)₂ (red ppt.) |
4. Identification of Chloride (Cl⁻) Ion
| Test | Reagent Used | Observation | Inference | Chemical Equation |
| Silver Nitrate (AgNO₃) test | AgNO₃ solution | White precipitate | Confirms Cl⁻ presence | NiCl₂ + 2AgNO₃ → 2AgCl (ppt.) + Ni(NO₃)₂ |
| Conc. Sulfuric Acid (H₂SO₄) test | H₂SO₄ + heat | Colorless pungent gas (HCl) turns moist blue litmus paper red | Confirms Cl⁻ presence | NiCl₂ + H₂SO₄ → 2HCl + NiSO₄ |
Conclusion
The qualitative analysis of NiCl₂ confirms the presence of nickel (Ni²⁺) and chloride (Cl⁻) ions through distinct chemical reactions, solubility tests, and confirmatory tests.