Sr(NO₃)₂ (Strontium Nitrate) Salt Analysis – CBSE Class 12Sr(NO₃)₂ (Strontium Nitrate) Salt Analysis – CBSE Class 12
1. Preliminary Examination
- Appearance: White crystalline solid, soluble in water.
- Flame Test: Bright red (crimson) flame characteristic of strontium ions.
2. Dry Heating Test
- Observation: On heating, decomposes to give brown nitrogen dioxide fumes and leaves residue of strontium oxide.
- Chemical Reaction: 2Sr(NO₃)₂ → 2SrO + 4NO₂↑ + O₂↑
3. Group Analysis
Strontium (Sr²⁺) belongs to Group V: Alkaline Earth Group.
- Group Reagent: (NH₄)₂CO₃ in the presence of NH₄Cl and NH₄OH.
- Group Precipitate: White carbonate precipitate (SrCO₃), insoluble in ammonium carbonate solution.
- Observation of characteristic red flame helps in flame test confirmation.
4. Confirmatory Tests for Sr²⁺ (Strontium Ion)
| Test | Procedure | Observation | Inference | Chemical Reaction |
|---|
| Flame Test | Place salt on platinum wire and heat in non-luminous flame. | Bright red (crimson) flame | Presence of Sr²⁺ | Sr²⁺ → Sr* → emits red color on excitation (physical process) |
| Action with (NH₄)₂CO₃ | Add ammonium carbonate to salt solution containing NH₄Cl & NH₄OH. | White precipitate of SrCO₃ | Sr²⁺ confirmed | Sr(NO₃)₂ + (NH₄)₂CO₃ → SrCO₃↓ + 2NH₄NO₃ |
| With Dilute H₂SO₄ | Add dilute sulphuric acid to salt solution. | White ppt. of SrSO₄ (insoluble in acids) | Sr²⁺ confirmed | Sr(NO₃)₂ + H₂SO₄ → SrSO₄↓ + 2HNO₃ |
5. Test for Anions (NO₃⁻: Nitrate)
| Test | Procedure | Observation | Inference | Chemical Reaction |
|---|
| Brown Ring Test | Add FeSO₄ to acidified solution of salt, then carefully add concentrated H₂SO₄ along the side of the test tube. | Brown ring formed at junction of two liquids | Nitrate (NO₃⁻) present | NO₃⁻ + Fe²⁺ + H⁺ → [Fe(H₂O)₅(NO)]²⁺ (brown ring complex) |
| Heating with FeSO₄ and Sulfuric Acid | Heat salt solution with FeSO₄ and concentrated H₂SO₄. | Brown ring formation | Confirms nitrate ion | Same as above |
6. Summary of Identification
- Group: V (Alkaline Earth Group)
- Cation: Sr²⁺ (Strontium)
- Anion: NO₃⁻ (Nitrate)
- Salt: Sr(NO₃)₂ (Strontium Nitrate)
7. Important Notes
- Strontium gives a characteristic bright red flame; this is key for identification.
- Use ammonium carbonate in ammoniacal medium for group separation and precipitation.
- Confirm nitrate presence with brown ring test.