Qualitative Tests

Salt Colour

Blue: Copper.

Green: Salts of Fe(II), NI, Cu or Cr.

Brown: Salts of Fe(II), Fe(III), PbO₂, Bi₂O₃

Pink: Mn, Co

Red: Hgo, HgI₂, Pb₃O₄

Orange: Sb₂S₃.

Gas Colour and odours

Colourless Odourless

O₂, CO₂, N₂.

Colourless

NH₃ : Pungent smelling
HCl : Pungent smelling
SO₂ : Smell of burning rubber
CH₃COOH : Vinegar smell.

Coloured

NO₂ : Brown, turns starch paper blue
Br₂ : Reddish Brown
I₂ : Violet, turns starch paper blue
Cl₂ : Greenish yellow

Anions which evolve gases
on action of dil HCl/dil H₂SO₄

Carbonates CO₃^2—

Sulphites SO₃^2—

Nitrites NO₂^—

• Evolves NO₂ on action of dil HCl or dil H₂SO₄

• Add dil Acetic Acid + FeSO₄ → [Fe(H₂O)₅NO]SO₄

Acetates CH₃COO^—

• Evolves CH₃COOH on action of dil HCl or dil H₂SO₄
  
• Gives Red coloured ppt with Neutral FeCl₃ → (CH₃COO)₃Fe

Thiosulphates S₂O₃^2—

• Evolves SO₂ on action of dil HCl or dil H₂SO4 along with Sulphur
  
• Decolourises I₂ solution
• Gives ppt with Ag⁺, Pb²⁺, Ba²⁺ but NOT with Ca²⁺

Thiosulphates S₂O₃^2—

• Evolves SO₂ on action of dil HCl or dil H₂SO4 along with Sulphur
  
• Decolourises I₂ solution
• Gives ppt with Ag⁺, Pb²⁺, Ba²⁺ but NOT with Ca²⁺

Anions which evolve gases
on action of Conc H₂SO₄

Chlorides Cl^—

Evolves HCl with Conc H₂SO₄

Evolves Cl₂ with MnO₂

Gives white ppt with Ag⁺ , Pb²⁺ salts

Chromyl Chloride test: 

i) Add K₂Cr₂O₇ & Conc H₂SO₄ → Red Fumes

ii) Pass fumes through NaOH → Yellow Solution

iii) Add Pb(CH₃COO)₂ solution → Yellow ppt

*Not given by covalent Chorides such as AgCl, HgCl₂, SbCl₃, most organic chlorides and SnCl₄

Bromides Br^—

Evolves Br₂ with Conc H₂SO₄

Evolves Br₂ with MnO₂

Gives Pale Yellow ppt with Ag⁺

Liberates with Br₂ with Chlorine water

Gives with White ppt with Pb²⁺

Nitrates NO₃^—

Evolves NO₂ with Conc H₂SO₄

Brown Ring Test

Add FeSO₄ + Conc H₂SO₄ → [Fe(H₂O)₅NO]SO₄

Here we use Conc H₂SO₄ where as in Nitrites(NO₂^—) we use
CH₃COOH {or dil H₂SO₄ can also be used}.

Independent Anions

Nitrates NO₃^—

Evolves NO₂ with Conc H₂SO₄

Brown Ring Test

Add FeSO₄ + Conc H₂SO₄ → [Fe(H₂O)₅NO]SO₄

Here we use Conc H₂SO₄ where as in Nitrites(NO₂^—) we use CH₃COOH
{or dil H₂SO₄ can also be used}.

Sulphates SO₄^2—

White ppt with Ba²⁺

Yellow ppt with Hg²⁺

Chromates CrO₄^2—

Yellow ppt with Ba²⁺

Red ppt with Ag⁺

Yellow ppt with Pb²⁺

Blue colour in ethereal layer on addition of H₂O₂

due to formation of CrO₅

Cations

Group I

^{Insoluble Chlorides ; they give precipitates with dil HCl}

Ag+

White ppt with Cl^— (dil HCl)

Yellow ppt with I^—

Brown ppt with NH₄OH but dissolves in excess

Yellow ppt with Na₂HPO₄

Pb²⁺

White ppt with Cl^— (dil HCl) Soluble in Conc HCl

Yellow ppt with I- Soluble in Excess

White ppt with NaOH but dissolves in excess

White ppt with NH₄OH

Yellow ppt with CrO₄^2—

White ppt with CN^—

Hg₂²⁺

White ppt with Cl^—

Green ppt with I^— however in Excess black ppt of Hg is obtained

Black ppt with NaOH but dissolves in excess

Disproportionates in NH₄OH → Hg + HgO.Hg(NH₂)Cl + NH₄Cl

Brick red ppt with CrO₄^2—

Group IIa

^{These DO NOT dissolve in yellow ammonium sulphides}

Cu²⁺

Black ppt with H₂S in presence of dil HCl

White ppt (Cu₂I₂) with I^— But excess I^— gives Brown colour due to I₃^—

Chocolate brown ppt with K₄[Fe(CN)₆] → Cu₂[Fe(CN)₆]

Blue ppt in NH₄OH but dissolves in excess to give blue solution

Black ppt turning White with SCN^— → Cu(SCN)₂ → CuSCN + (SCN)₂

Bi³⁺

Brown ppt with H₂S in presence of dil HCl

White ppt with NaOH, ppt dissolves in acid and when boiled
becomes yellow due to formation of BiO.OH

Black Ppt with I^—, but with excess it gives orange colour due to
formation of BiI₄^—

Bi Salts when poured in excess water gives salt white ppt of BiO.(?)
eg. BiOCl or BiO(NO₃)

Cd²⁺

Yellow ppt with H₂S in presence of dil HCl

White ppt with NH₄OH, ppt dissolves in excess

White Ppt with CN^—, but with excess it dissolves and regenerates
Yellow ppt with H₂S (Not so with others)

No ppt with I^—

Group IIb

^{These dissolve in yellow ammonium sulphides}

Sn²⁺

Brown ppt with H₂S in dil HCl

White ppt with NaOH, ppt dissolves in excess

White ppt with NH₄OH

White Ppt with HgCl₂

Sn⁴⁺

Yellow ppt with H₂S in dil HCl

Gelatinous white ppt with NaOH, ppt dissolves in excess

White ppt with NH₄OH

White Ppt with HgCl₂

As and Sb are NOT in JEE Main and JEE Advanced

Group III

Fe³⁺

Brown ppt with NH₄OH in NH₄Cl

Reddish Brown ppt with NaOH

Prussian Blue ppt with K₄[Fe(CN)₆]

Brown colouration is obtained with K₃[Fe(CN)₆

Yellowish ppt with Na₂HPO₄ → FePO₄

Deep Red colour with SCN^—

Al³⁺

White ppt with NH₄OH in NH₄Cl

White ppt with NaOH but dissolves in excess

White ppt with Na₂HPO₄

White ppt with Co(NO₃)₂ which glows when hot

Cr³⁺

Green ppt with NH₄OH in NH₄Cl

Green ppt with NaOH

Green ppt with NH₄OH but dissolves in excess

CrO₄^2— gives Blue colour to ether layer with H₂O₂ and dil H₂SO₄

CrO₄^2— gives Violet colour with Diphenylcarbazide

Group IV

Zn²⁺

Dirty white ppt with NH₄OH in NH₄Cl

Gelatinous white ppt with NaOH dissolves in excess

Gelatinous white ppt with NH4OH dissolves in excess

White ppt with Na₂HPO₄

White ppt with K₄[Fe(CN)₆]

White ppt with Na₂[Hg(SCN)₄]

Red ppt with Diphenylthiocabazone

Mn²⁺

Pink/buff ppt with NH₄OH in NH₄Cl

white ppt with NaOH But turns Brown with air MnO(OH)₂

Pinkish white ppt with NH₄OH dissolves in ammonium salts

Pink ppt with Na₂HPO₄ → Mn(NH₄)PO₄

Purple colour solution with PbO₂ in acidic medium → HMnO₄ Also with NaBiO₃/H⁺

Ni²⁺

Black ppt with NH₄OH in NH₄Cl

Green ppt with NaOH

Green ppt with NH₄OH dissolves in excess to give deep blue solution.

Rosy Red ppt with DMG

(Although not in Adv syllabus But is present in Main syllabus)

Group V

Ba²⁺

White ppt with (NH₄)₂CO₃ in NH₄Cl

Yellow ppt with Na₂CrO₄

White ppt with any sulphate Dissolves appreciably in boiling H₂SO₄

White ppt with oxalates

Sr²⁺

White ppt with (NH₄)₂CO₃ in NH₄Cl

Yellow ppt with Na₂CrO₄

White ppt with any sulphate Dissolves slightly in boiling H₂SO₄

Ca²⁺

White ppt with (NH₄)₂CO₃ in NH₄Cl

Yellow ppt with Na₂CrO₄

White ppt with any sulphate Dissolves slightly in boiling H₂SO₄

White ppt with K₄[Fe(CN)₆] Different than Ba²⁺ and Sr²⁺

Group VI

Mg²⁺

Gelatinous White ppt with NH₄OH Readily soluble in ammonium salts

With Na₂CO₃ in absence of NH₄⁺ ions give ppt of basic
magnesium carbonate MgCO₃.Mg(OH)₂.5H₂O

In presence of NH₄⁺ ions NH₄⁺ + CO₃^2— → NH₃ + HCOO₃^—
This is reason why Mg²⁺ is added to group VI

White ppt with Na₂HPO₄/NH₄⁺