QUALITATIVE ANALYSIS of anions - introduction.ppt

Analysis of anions

1. QUALITATIVE ANALYSIS
OF THE ANIONS
Dr. Ahmad F Eweas
1

2. What are the Anions ?
•Anions are ions bearing a negative charge; they are formed from
non-metallic elements due to gain of electrons.
Why we should analyze Anions ?
•Some anions are necessary for human life.
•Some anions are used for different pharmaceutical purposes as sulphates and
carbonates.
• Some anions are environmental hazards that cause great risk to human
health as cyanides and nitrites.
•The conc. in the body is related to the health statusThe conc. in the body is related to the health status

3. Anions are classified by 2 different modes:
A.according to the identification by the volatile products obtained on
treatment with acids.
1. Gases evolved with dil. HCl or H
2SO
4
2. Gases or vapors evolved with conc. H
2
SO
4
3. Miscellaneous group
B.according to the identification by the reactions in solutions (according to
their solubilities)
1. Precipitation reactions
2. oxidation-reduction reactions
Classification of AnionsClassification of Anions

4. Classification of AnionsClassification of Anions
Mixture of many Anions

5. Group Anions Reagent Gases evolved
Precipitates
I Carbonates, hydrogen carbonate,
sulphite, thiosulphate, sulphide, nitrite,
cyanide
Dil. HCl
CO
2
, SO
2
, H
2
S, NO
2
,
HCN
II Flouride, chloride,
Bromide, iodide, nitrate
Chlorate, perchlorate,
Permanganate and organic anions
conc.
H
2
SO
4
HF, HCl, HBr, HI,
IIISulphates and phosphates BaCl
2
BaSO
4

Ba
3 (PO4)
2

6. Nitrite(NO
2
-
): is one of the most toxic environmental contaminant that
causes great risks to general human health.
Carbonate (CO
3
2-
), Bicarbonate (HCO
3
-
), Sulphide (S
2-
) , Thiosulphate (S
2
O
3
2-
),
Sulphite (SO
3
2-
), Nitrite(NO
2
-
), Cyanide(CN
-
)
Anions of Group I
Cyanide(CN
-
) : is one of the most toxic environmental contaminant that
causes great risks to general human health.

7. Analysis of Group I AnionsAnalysis of Group I Anions
Anion Dil HCl equations
CO
3
2-
Effervescence due to evolution of CO
2
gas
which renders lime water turbid
CO
3
2-
+ 2H
+
= CO
2
↑ + H
2
O
CO
2
+ Ca(OH)
2
= CaCO
3
+ H
2
O
HCO
3
-
Effervescence due to evolution of CO
2
gas
which renders lime water turbid
HCO
3
-
+ H
+
= CO
2
↑ + H
2
O
CO
2
+ Ca(OH)
2
= CaCO
3
+ H
2
O
SO
3
2-
evolution of SO
2
gas characterized by its
suffocating odor of burning (Sº) which turns
acidified dichromate paper green
SO
3
2-
+ 2H
+
= SO
2
↑ + H
2
O
SO
2
+ Cr
2
O
7
-2
+ 2H
+

= 2 Cr
3+
+ 3SO
4
2-
+ H
2
O
S
2
O
3
2-
No immediate change on cold, then (Sº) is
ppt, on boilingSO
2
gas volutes
S
2
O
3
2-
+ 2H
+
= SO
2
↑+ H
2
O + S↓
S
2-
evolution of H
2
S gas characterized by its odor
of bad egg which turns lead acetate paper
black
S
2-
+ 2H
+
= H
2
S ↑
H
2
S + Pb
2+
= PBS↓ black ppt
NO
2
-
Pale blue liquid + evolution of NO
2
brown
fumes
NO
2
-
+ H
+
= HNO
2
↑ + H
2
O
3HNO
2
= HNO
3
+ H
2
O + 2NO
2NO ↑ + O
2
↑ = 2NO
2
↑ (brown)

8. Analysis of Group I AnionsAnalysis of Group I Anions
Anion BaCl
2 reagent ph.ph. test AgNO
3 reagent
CO
3
2-
White ppt of BaCO
3
CO
3
2-
+ Ba
2+
= BaCO
3
↓
Pink colored
solution
White ppt of Ag
2CO
3 turns dark by
xss reagent
CO
3
2-
+ 2Ag
+
= Ag
2
CO
3
↓
HCO
3
-
White ppt of BaCO
3 on
boiling
2HCO
3
-
+ Ba
2+

= BaCO
3
↓+CO
2
↑ + H
2
O
Colorless
solution
- Ve
SO
3
2-
White ppt of BaSO
3
SO
3
2-
+ Ba
2+
= BaSO
3
↓
Alkaline to
litmus paper
White crystal ppt of Ag
2SO
3 dissolve
by xss reagent
SO
3
2-
+ 2Ag
+
= Ag
2
SO
3
↓
S
2O
3
2-
White ppt of BaS
2
O
3
S
2O
3
2-
+ Ba
2+
= BaS
2O
3 ↓
White ppt of Ag
2
SO
3
turns black on
standing
S
2O
3
2-
+ 2Ag
+
= Ag
2S
2O
3 ↓
Ag
2
S
2
O
3
↓+H
2
O = Ag
2
S↓+ SO
4
2-
S
2-
- Ve Black ppt of Ag
2
S↓
2Ag
+
+S
2-
= Ag
2S↓
NO
2
-
- Ve White crystal ppt of AgNO
2

Ag
+
+NO
2
-
= AgNO
2↓

9. Analysis of Group I AnionsAnalysis of Group I Anions
Anion Lead acetate
reagent
MgSO
4
reagent
Iodine solutionKMnO
4 + H
2SO
4
CO
3
2-
-Ve White ppt of
MgCO
3
-Ve -Ve
HCO
3
-
-Ve -Ve
And give +Ve
result on
boiling
-Ve -Ve
SO
3
2-
White ppt of PbSO
3
SO
3
2-
+ Pb
2+
= PbSO
3
↓
-Ve Decolorization of
violet color
S
2O
3
2-
White ppt of PbSO
3 soluble in xss
S
2
O
3
2-
, ppt turns black upon
boiling
S
2
O
3
2-
+ Pb
2+
= PbS
2
O
3
↓
PbS
2
O
3
↓+H
2
O =PbS↓+ SO
4
2-
-Ve Decolorization of
the brown color
S
2-
Black ppt of PbS
H
2
S + Pb
2+
= PBS↓
-Ve -Ve -Ve
NO
2
-
-Ve -Ve -Ve -Ve

10. Anion Specific tests
S
2-
Sodium nitroprusside test
Sulphide solution + KOH solution + Sodium nitroprusside → purple color is
formed
S
2-
+ [Fe(CN)
5
NO]
2-
→ [Fe(CN)
5
NOS]
4-

S
2O
3
2-
Blue ring test
S
2
O
3
2-
+ conc. H
2
SO
4
+ ammonium molybdate (solution slowly down the side of
test tube) →blue ring is formed temporarily at the contact zone
NO
2
-
Brown ring test
FeSO
4 (25%) + dil H
2SO
4 or acetic acid + NO
2
-
(solution slowly down the side of
test tube) →brown ring is formed temporarily at the junction of the 2 liquids
NO
2
-
+ H
+
= HNO
2 ↑
3HNO
2
= HNO
3
+ H
2
O + 2NO
NO ↑ + FeSO
4
= [Fe, NO]SO
4
(brown ring)
Analysis of Group I AnionsAnalysis of Group I Anions

11.  Nitrate(NO
3
-
): is one of the most toxic environmental contaminant that causes
great risks to general human health.

Bromide(Br
-
) : is one of the most toxic environmental contaminant that causes
great risks to general human health.
Flouride(F
-
) : is one of the most important agents used in formulation of tooth
paste for protecting teeth from caries.
Permanganate (MnO
4
-
): is one of the most important agents used as antiseptic
solution for wound healing.
Potassium halides are used as sedative (Br
-
), anti-hypokalemia (Cl
-
), anti-thyroid
(I
-
), antiseptic (MnO
4
-
).
•Flouride(F
-
), Chloride(Cl
-
), Bromide(Br
-
), Iodide(I
-
), Nitrate(NO
3
-
),
Chlorate(ClO
3
-
), Perchlorate(ClO
4
-
), Permanganate (MnO
4
-
) and Organic
anions
Anions of Group II

12. Analysis of Group II AnionsAnalysis of Group II Anions
Anion Conc. H
2SO
4 equations
F
-
Evolution of colorless corrosive H
2
F
2
gas which
turns the blue litmus paper red and the test tube
acquires a greasy appearance due to the
action of the gas on the silica of the glass
2F
-
+ H
2
SO
4
= H
2
F
2
↑ + SO
4
2-
H
2
F
2
+ SiO
2
= SiF
4
↑ + 2H
2
O
3SiF
4 + 3H
2O = 2[SiF
6]
2-
+ H
2SiO
3 ↓+ 4H
+
Cl
-
Evolution of HCl gas with its pungent odour, turns
the blue litmus paper red and forms white
clouds near the mouth with NH
3
paper
Cl
-
+ H
2
SO
4
= HCl ↑ + HSO
4
-

HCl

+ NH
3
= NH
4
Cl
Br
-
Evolution of orange-red fumes of HBr gas which
changes into redish-brown fumes of bromine
Br
-
+ H
2
SO
4
= HBr ↑ + HSO
4
-

Br
-
+ H
2
SO
4
= Br
2
+ SO
4
2-
+ SO
2
+ H
2
O
I
-
Evolution of violet vapours of I
2
Which turns the
starch paper paper blue
I
-
+ H
2
SO
4
= HI ↑ + HSO
4
-

I
-
+ H
2
SO
4
= I
2
+ SO
4
2-
+ SO
2
+ H
2
O
NO
3
-
Evolution of NO
2 red-brown vapours NO
3
-
+ H
2SO
4 = NO
2↑ + H
2O + O
2↑ +
SO
4
2-
(brown)

13. Analysis of Group II AnionsAnalysis of Group II Anions
Anion AgNO
3
reagent Lead acetate reagent
F
-
-Ve -Ve
Cl
-
Curdy white ppt of AgCl soluble in
dil, ammonia
Cl
-
+ Ag
+
= AgCl ↓

Curdy white ppt of PbCl
2
soluble in hot
water
2Cl
-
+ Pb
+2
= PbCl
2
↓
Br
-
Curdy pale –yellow ppt of AgBr
soluble in conc. ammonia
Br
-
+ Ag
+
= AgBr ↓
White crystals of PbBr
2 soluble in boiling
water
2Br
-
+ Pb
+2
= PbBr
2
↓
I
-
Curdy yellow ppt of AgI insoluble in
conc. ammonia
I
-
+ Ag
+
= AgI ↓
Golden yellow crystals of PbI
2
2I
-
+ Pb
+2
= PbI
2
↓
NO
3
-
- Ve - Ve

14. Anion Specific tests
F
-
CaCl
2 test
Slimy white ppt of CaF
2 soluble in dil. HCl
2F
-
+ Ca
+2
= CaF
2 ↓
Fe(Cl)
3
test
White crystals of Na
3
[FeF
6
]

soluble in water
6F
-
+ Fe
+3
+ 3 Na
+
= Na
3
[FeF
6
] ↓
Cl
-
Chromyl chloride test
Cl
-
(solid)+ Cr
2
O
7
2-
(solid) + conc. H
2
SO
4
+ warming →deep red vapors of
chromyl chloride gas CrO
2
Cl
2
which form yellow solution of CrO
4
2-
on
passing in NaOH solution
4Cl
-
+ Cr
2
O
7
2-
+ 6H
+
+ warming → 2CrO
2
Cl
2
↑+ 3H
2
O
CrO
2
Cl
2
↑+ 4OH
-
→ CrO
4
2-

+ 2Cl
-
+ 2H
2
O
Br
-
Chlorine water test
Cl
2 (dropwise)+ Br
-
(solution) → deep orang-red vapours of Br
2 which forms
orange-red
Cl
2 + 2Br
-
→ Br
2 + 2Cl
-

Analysis of Group II AnionsAnalysis of Group II Anions

15. Anion Specific tests
Br
- Fluorescein test
Yellow fluorescein → red eosin
I
- CuSO
4
test
Forms brown ppt of Cu
2I
2 and I
2 (4I
-
+ 2Cu
+2
= Cu
2I
2 ↓ + I
2 )
HgCl
2
test
Forms scarlet-red ppt of HgI
2 soluble in excess iodide
2I
-
+ HgCl
2
= HgI
2
↓ + 2Cl
-
NO
3
- Brown ring test
FeSO
4
(25% saturated solution) + NO
3
-
(solution) + conc. H
2
SO
4
(slowly down
the side of test tube) →brown ring is formed temporarily at the junction of the
2 liquids
2NO
3
-
+ 6Fe
2+
+8H
+
= 6Fe
3+
+2NO ↑+ 4H
2
O
NO ↑ + FeSO
4
= [Fe, NO]SO
4
(brown ring)
Analysis of Group II AnionsAnalysis of Group II Anions

16. Sulphates (SO
4
2-
):
1. 1. ferrous- sulphate, and phosphate are used as iron supplements in ferrous- sulphate, and phosphate are used as iron supplements in
tonics preparationstonics preparations
2. Barium sulphate is used in taking barium-ray photographs of the 2. Barium sulphate is used in taking barium-ray photographs of the
stomach and intestines.stomach and intestines.
3. Magnesium sulphate is used as laxative3. Magnesium sulphate is used as laxative
Phosphates (PO
4
3-
) : is one of the most common electrolyte and
buffers used in general human preparations.
Miscellaneous group
Sulphates (SO
4
2-
) and Phosphates (PO
4
3-
)
Anions of Group III

17. Analysis of Group III AnionsAnalysis of Group III Anions
Anion AgNO
3
reagent BaCl
2
reagent Lead acetate
reagent
SO
4
2-
White crystalline ppt of
Ag
2SO
4
SO
4
-2
+2Ag
+
= Ag
2SO
4 ↓
White ppt of BaSO
4
insoluble in dil HCl and
HNO
3
SO
4
-2
+ Ba
+2
= BaSO
4 ↓

White ppt of PbSO
4
soluble in conc. H
2SO
4
and ammonium
acetate
SO
4
-2
+ Pb
+2
= PbSO
4
↓
PO
4
3-
yellow ppt of Ag
3
PO
4

soluble in dil, nitric acid
and ammonia
PO
4
-3
+3Ag
+
= Ag
3PO
4 ↓

white ppt of BaHPO
4

soluble in dil, mineral
acids and ammonia
HPO
4
-2
+Ba
+2
= BaHPO
4 ↓
-Ve

18. Analysis of Group III AnionsAnalysis of Group III Anions
Anion Hg (NO
3
)
2
reagent Magnesia mixture reagent
SO
4
2-
Yellow ppt of basic HgSO
4
.
2HgO
SO
4
-2
+ 3Hg
+2
+ 2 H
2
O =
HgSO
4
. 2HgO↓ + 4 H
+
-Ve
PO
4
3-
-Ve
white crstalline ppt of Mg(NH
4)PO
4 soluble in
dil, mineral acids
HPO
4
-2
+Mg
+2
+ NH
3
= Mg(NH
4
)PO
4
↓

19. Anion Specific tests
PO
4
3-Ammonium molybdate test
Yellow crystalline ppt of ammonium phospho-
molybdate
NH
4
+
+ PO
4
-3
+ H
+
+ MoO
4
2-
= (NH
4)
3PO
4 + MoO
3 ↓ + H
2O
Analysis of Group III AnionsAnalysis of Group III Anions