Sr(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.