Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

Chemistry Class 12

Class 12 : Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

The document Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev is a part of the Class 12 Course Chemistry Class 12.
All you need of Class 12 at this link: Class 12

Charcoal Cavity Test:
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

Cobalt Nitrate Test:
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

Flame test :
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

Borax Bead test:
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

Analysis of ANIONS (Acidic Radicals) :
(a) DILUTE SULPHURIC ACID/DILUTE HYDROCHLORIC ACID GROUP 
:
1. CARBONATE ION (COs2-3) :

  • Dilute H2SO4 test : A colourless odourless gas is evolved with brisk effervescence.
    CaCO3 + H2SO4 → CaSO4 + H2O + CO2
  • Lime water/Baryta water (Ba(OH)2) test:
    CO2 + Ca(OH)2 → CaCO3↓, (milky) + H2O
    Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

2. SULPHITE ION ( SO32-) :

  • Dilute H2SO4 test :
    CaSO3 + H2SO4 → CaSO4 + H2O + SO2↑ ; SO2 has suffocating odour of burning sulphur.
  • Acidified potassium dichromate test : The filter paper dipped in acidified K2Cr2O7 turns green.
    Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev
  • Barium chloride/Strontium chloride solution :Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

White precipitate dissolves in dilute HCI. BaSO3 ↓ + 2H+ → Ba2+ + SO2 ↑ + H2O.

3. SULPHIDE ION (S2-):

  • Dilute H2SO4 test : Pungent smelling gas like that of rotten egg is obtained.
    S2- + 2H+ → H2S↑
  • Lead acetate test : (CH3COO)2Pb + H2S → PbS↓ (black) + 2CH3COOH. 
  • Sodium nitroprusside test: Purple coloration is obtained.
    S2- + [Fe(CN)5 (NO)]2- → [Fe(CN)5NOS]4- (violet).
  • Cadmium carbonate suspension/ Cadmium acetate solution :
    Na2S + CdCO3 → CdS↓ (Yellow) + Na2CO3

4. NITRITE ION ( NO-2):

  • Dilute H2SO4 test :
    NO2- + H+ → HNO2 ; (2 HNO2 → H2O + N2O3);
    3HNO2 → HNO3 + 2NO + H2O ; 2NO + O2 → 2NO2
  • Starch iodide test:
    Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

5. ACETATE ION (CH3COO-)

  • Dilute H2SO4 test : (CH3COO)2Ca + H2SO4 → 2CH3COOH (vinegar like smell) + CaSO4
  • Neutral ferric chloride test :
    Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

(b) CONC. H2SO4 GROUP :
1. CHLORIDE ION (Cl-):

  • Concentrated H2SO4 test : Cl- + H2SO4 → HCI (colourless pungent smelling gas) + HSO4-
  • NH4OH + HCI → NH4CI ↑ (white fumes) + H2O.
  • Silver nitrate test : Cl- + Ag+ → AgCI↓ (white)

White precipitate is soluble in aqueous ammonia and precipitate reappears with HNO3.
AgCI + 2NH4OH → [ Ag(NH3)2]CI (Soluble) + 2H2O ; [Ag(NH3)2]CI + 2H+ → AgCI↓ + 2NH4+.

  • Chromyl chloride test:Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev
    2. BROMIDE ION (Br-) :
  • Concentrated H2SO4 test :
    2NaBr + H2SO4 → Na2SO4 + 2HBr ; 2HBr + H2SO4→ Br2 ↑ (reddish-brown) + 2H2O + SO2
  • Silver nitrate test : NaBr + AgNO3 → AgBr↓ (pale yellow) + NaNO3

Yellow precipitate is partially soluble in dilute aqueous ammonia but readily dissolves in concentrated ammonia solution. AgBr + 2NH4OH → [Ag(NH3)2] Br + H2O

  • Chlorine water test (organic layer test):
    2Br- + Cl2 → 2CI- + Br2 ↑.
    Br2 + CHCI3 / CCI4 → Br2 dissolve to give reddish brown colour in organic layer.
    3. IODIDE ION (I-) :
  • Concentrated H2SO4 test : 2Nal + H2SO4 → Na2SO4 + 2HI
    2HI + H2SO4 → l2 ↑ (pungent smelling dark violet) + 2H2O + SO2
  • Starch paper test: Iodides are readily oxidised in acid solution to free iodine; the free iodine may than be identified by deep blue colouration produced with starch solution.
    3I- + 2NO2- + 4H+ → l3- + 2NO ↑ + 2H2O.
  • Silver nitrate test : Bright yellow precipitate is formed.
    I- + Ag+ → Agl↓

Bright yellow precipitate is insoluble in dilute aqueous ammonia but is partially soluble in concentrated ammonia solution.

  • Chlorine water test (organic layer test):
    2Nal + Cl2 → 2NaCI + l2
    l2 + CHCI3 → l2 dissolves to give violet colour in organic layer.
    4. NITRATE ION (NO3-) :
  • Concentrated H2SO4 test: Pungent smelling reddish brown vapours are evolved.
    Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

Addition of bright copper turnings or paper pellets intensifies the evolution of reddish brown gas.

Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

  • Brown ring test:
    Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

3. Miscellaneous Group :
1. SULPHATE ION (SO42-) :

  • Barium chloride test : Na2SO4 + BaCI2 → BaSO4↓ (white) + 2NaCI.

White precipitate is insoluble in warm dil. HNO3 as well as HCI but moderately soluble in boiling concentrated hydrochloric acid.

  • Lead acetate test : Na2SO4 + (CH3COO)2Pb → PbSO4 ↓ (White) + 2CH3COONa

White precipitate soluble in excess of hot ammonium acetate.
PbSO4 + 2CH3COONH4 → (CH3COO)2Pb (soluble) + (NH4)2SO4
2. PHOSPHATE ION (PO43-):

  • Ammonium molybdate test:
    Na2 HPO4 (aq) + 12(NH4)2MoO4 + 23HNO3 → (NH4)3PMo12O40↓ (canary yellow) + 2NaNO3 + 21NH4NO3 + 12H2O

ANALYSIS OF CATIONS
1. AMMONIUM ION (NH4+) :
2NH3 + Mn2+ + H2O2 + H2O → MnO(OH)2 ↓ (brown) + 2NH4+

Nessler's reagent (Alkaline solution of potassium tetraidomercurate(ll):Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

Ist GROUP (Pb2+, Hg22+, Ag+):
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

IIA Group (Hg2+, Pb2+, Bi3+, Cu2+, Cd2+)
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

IIB Group (As3+, Sb3+, Sn2+, Sn4+)
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

IIIrd Group (Al+3, Cr+3, Fe+3)
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

IVth GROUP (Zn2+, Mn2+, Ni2+, Co2+)
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev
Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

Vth Group (Ba2+, Sr2+, Ca2+) :

Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev

VIth GROUP :
MAGNESIUM ION (Mg2+) :

Chapter - 12 QUALITATIVE ANALYSIS Class 12 Notes | EduRev
Titan Yelllow (a water soluble yellow dyestuff): It is adsorbed by Mg(OH)2 producing a deep red colour or precipitate.

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