SS3: CHEMISTRY – 1ST TERM Qualitative Analysis III | Week 6 Identification of Anions

Lesson 6, Topic 2

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Identification of Anions

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Test for SO₄^2-, SO₃^2-, CO₃^2-and S^2- using dilute BaCl_2(aq) and HCl_(aq) or Ba(NO₃)_2(aq) and HNO_3(aq)as test reagents

Test	Observation	Inference
Sample solution + BaCl_2(aq) + HCl_(aq) in excess	White precipitate formed. Precipitate insoluble in excess HCl_(aq)	SO₄^2-, SO₃^2-, CO₃^2-or S^2- present SO₄^2- present
Sample solution + BaCl_2(aq) + HCl_(aq) in excess	White precipitate formed. A colourless gas with a chocking smell is given off. Gas turns potassium dichromate (IV) paper from orange to green.	SO₄^2-, SO₃^2-, CO₃^2-or S^2- present SO₃^2- is present. Gas is SO₂ gas
Sample solution + BaCl_2(aq) + HCl_(aq) in excess	White precipitate formed. A colourless gas with a chocking smell is given off. Gas turns potassium dichromate (IV) paper from orange to green.	SO₄^2-, SO₃^2-, CO₃^2-or S^2- present SO₃^2- is present.Gas is SO₂ gas
Sample solution + BaCl_2(aq) + HCl_(aq) in excess	White precipitate formed. Effervescence occurs, a colourless, odourless gas which turns moist blue litmus red and lime water milky is given off.	SO₄^2-, SO₃^2-, CO₃^2-or S^2- present Acidic gas is present. Gas is CO₂from CO₃^2- or HCO₃^–
Sample solution + BaCl_2(aq) + HCl_(aq) in excess	White precipitate formed. A colourless gas with rotten egg smell is given off. Gas turns lead (II) ethanoate paper black.	SO₄^2-, SO₃^2-, CO₃^2-or S^2- present S^2- present.Gas is H₂S
Sample solution +HCl_(aq) +BaCl_2(aq)	No visible reaction. White precipitate formed. Precipitate is insoluble.	SO₄^2- present

Test for SO₃^2-, CO₃^2-, S^2- , Cl^– and I^– using AgNO_3(aq) and HNO_3(aq)

Test	Observation	Inference
Sample solution +AgNO_3(aq) + dil. HNO_3(aq) in excess	White precipitate Precipitate insoluble in excess HNO_3(aq)	SO₃^2-, CO₃^2-, Cl^– or S^2- present SO₃^2-; S^2- or Cl^– present
Sample solution +AgNO_3(aq) + dil. HNO_3(aq) in excess	White precipitate Effervescence occurs, a colourless, odourless gas which turns moist/damp/wet blue litmus red and lime water milky is given off.	SO₃^2-, CO₃^2-, Cl^– or S^2- present Gas is CO₂ from CO₃^2- or HCO₃^–. Gas is acidic.
Sample solution +AgNO_3(aq) + dil. HNO_3(aq) in excess	White precipitate White precipitate formed. Precipitate soluble in excess NH₃(aq)	SO₃^2-, CO₃^2-, Cl^– or S^2- present Cl^– present
Sample solution +AgNO_3(aq) + dil. HNO_3(aq) in excess	White precipitate Yellow precipitate formed. Precipitate insoluble in concentrated NH_3(aq)	SO₃^2-, CO₃^2-, Cl^– or S^2- present I^– present

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