This document provides information about various inorganic anions and how to identify them using chemical tests. It discusses the solubility rules and reactions of carbonate, bicarbonate, sulphide, nitrite, nitrate, chloride, bromide, iodide, sulphate and other anions. Various tests are described including gas evolution reactions, precipitation reactions using metal salts, and colorimetric tests using oxidizing agents to identify these anions.

1. Carbonate (CO3
2–) / Bicarbonate (HCO3
–)
Warm
Ca(OH)2
(Lime water)
Ba(OH)2
( )
Baryta water
(4)
(a)
(b)
(c)
(2)
(a) (b)
Test based on
redox prop.
Identification of liberated gas (Lab test)
dil.HCl/H SO
2 4
(Salt sol .)
n
K MnO (green)
2 4
KMnO4/H
+
K Cr O /H
2 2 7
+
No redox rxn.
CO (aq.)/ HCO (aq)
3
2– –
3
1. All CO salts are water insoluble except alkali metal carbonate salts and (NH ) CO
3 4 2 3
2–
.
2. All metal bicarbonate salts are water soluble. Except NaHC 3
O (Sparingly soluble)
Observation [Colourless odourless gas evolves with brisk effervescence]
CO gas
2
Note : 1.
2.
CO ion gives ppt. at room temp. whereas HCO ¯ ion forms ppt. of carbonate on boiling.
Water insoluble carbonate salts are soluble in soda water (CO + H O) and CH COOH.
3
3
2–
3
2 2
No redox rxn.
KMnO + MnO
4 2 (Dispn.rxn.)
(Pink sol )
n
(Orange sol )
n
H CO
2 3 is
non-oxidising
and hence
CO /CO
does not act
as oxidant
3 2
2–
BaCO3
(white turbidity)
CO2
Ba(HCO3 2
)
( )
colourless sol
n
Boil
BaCO3
CaCO3
( )
white turbidity
CO2
excess CO2
Ca(HCO3 2
)
( )
colourless sol
n
Boil
CaCO3
Precipitation test
(a) (b) (c)
BaCO3
white
BaCl2 soln
BaCl2
(sol )
n
Ag CO
2 3
white/yellow ppt.
dil.HCl dil.HNO3
Pb(NO )
3 2
(sol )
n
AgNO3 Soln
PbCO3
white ppt.
Boil
excess
NH sol
3
n
[Ag(NH )
3 2]
+
Ag O
2
Brown ppt.
(1)
excess CO2
(white turbidity) (white turbidity)
(soluble)
(3)
2HCO CO + CO + H O
3 3 2 2
– 2–
Boil
100°C
Pb(OAc) sol.
2

2. Sulphide (S2–)
1. All S2– salts of s-block metals are water soluble and colourless whereas S2– salts of p-block & d-block are water insoluble and usually coloured due to polarisation effect.
2. S2– salts of Al3+, Cr3+ and Mg2+ do not exist in aqueous solution because they readily hydrolysed into corresponding metal hydroxide due to their low Ksp, hence they are prepared
in dry condition.
FeS(black) + dil. 2HCl / dil. H2SO4(non-oxidising acid)
apparatus
Kipps
in
occurs
.
Rxn




 
 FeCl2 / FeSO4 + H2S
Warm
[Orange solution
of Cr O /H
2 7
2– +
turn green]
[Pink solution
of KMnO /H
4
+
is decolourised]
IO ¯/H
3
+
Colourless sol ]
n
[
I ¯solution (Brown)
3
(5)
(5)
(4)
(3)
Tests based
on ppt. Rn.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(2) (a)
(a)
(ii)
Specific tests
(i) (iii)
Negative test
(b)
(b)
(c)
H S
2 H S
2
Limited H S
2
Test based on
reducing prop.
Identification of gas by oxidising agents (Redox reaction)
dil.HCl
(Soda Ext.)
Cl /Br /I
2 2 2
CaOCl2
CaCl2/BaCl
Solution
2 Pb(OAc 2
solution
) AgNO3
solution
Ag2 (Black)
S
No ppt. Excess
H S gas
2
PbS (Black)
Insol.in Ex. NaOH
 Starch
CCl4
I¯ (aq.)
Colourless
Deep blue
colouration
I¯+violet
layer
Fe (aq)
3+
SO (g)
2
conc.
H SO
2 4
conc.H SO
2 4

H O
2 2
O3
(st.O.A.)
excess
HX
CaCl2
SO2
H SO
2 4
H SO
2 4
Fe (aq)
2+
S Yellow turbidity)

S
White
turbidity

S
S (aq.)
2–
Acidified
Na
[Fe(CN)
(NO)]
2
5
Alkaline
Na
[Fe(CN)
(NO)]
2
5
Na [Fe(CN) (NOS)]
Purple solution
4 5
(1)
Observation [Colourless poisonous gas having rotten egg smell, turns Pb(CH COO) paper black (PbS)]
3 2
Note : 1. Mn+ (p and d-block metal cation) forms metal suphides with H2S gas depending upon acidic, neutral, basic medium of solution
2. PbS (black) is insoluble in excess NaOH solution or excess NH4OH solution due to its low Ksp
3. Specific test with Na2[Fe(CN)5NO] (sodium nitroprusside) requires high conc. of S2– ion, hence neutral H2S and acidified H2S gives negative test, whereas alkaline H2S gives
purple colouration.

3. Nitrite (NO2¯) and Nitrate (NO3
–)
1. All NO2¯ salts are water soluble except NO2¯ salt of Ag+, Hg2
2+, Cu+
2. All NO3¯ salts are water soluble.
NO ¯ (aq)
2
NO ¯ (aq)
3 NO ¯ (s)
3
NH gas
3
FeSO + H SO
4 2 4
conc.
Deep blue
soln.
NO (brown gas)
2
HNO3
N O
2 5
[HNO2
HNO3 + NO
NO2 (brown gas)
H2O + N O ]
2 3
dil.HCl/dil.H SO
2 4
conc.H SO
2 4
conc.
H SO
2 4
30°C
40°C
–H O
2
–½O2
dil.HCl/dil.H SO
2 4
Disprop.
Warm
Air (Mouth of
test tube)
NO2(brown gas)
NO2(brown gas)
Warm
(1)
Warm
(1)
(2)
(Soda Ext.)
(Soda Ext.)
NO (aq.)
2¯
AgNO (white ppt.)
2 
NO (aq.) + Cr (aq.) / Mn (aq.)
3¯
3+ 2+
R.T.
Pale blue
transient colour
Colourless
ppt. reaction
St. Oxidising agents
Acidified Cr O
2 7
2–
(aq.)
/ MnO4
–
(aq.)
Test based on
Oxidising property (Brown ring specific test)
(Brown ring complex)
(Brown ring complex)
(Brown ring specific test)
(Yellow turbidity)
T
e
s
t
b
a
s
e
d
o
n
r
e
d
.
p
r
o
p
.
Test
based
on
Oxd.
prop.
KI
+
starch
[H]
(st.
R.A.)
(Zn/Al
+
NaOH)
AgNO soln.
3
(2)
(3)
(4)
H S
2
S + NO
 
NH gas
3
Deep blue solution + NO
[Fe(H O)
2 5(NO)]SO4
[Fe(H O)
2 5(NO)]SO4
KI + Starch
[H] (st.R.A.)
(Zn/Al + NaOH)
FeSO + dil.H SO
4 2 4
(a)
(b)
(c)
(a) (b) (c)
(d)
+1 +1
+1 +1
With piece of filter paper or copper turnings
evolution of reddish brown gas is intensified
Note: 1. Aq. soln. of M(NO2)2 / M(NO3)2 salts (M2+ = Ba+2, Sr+2, Pb2+) do not give brown ring test because these cations form insoluble SO4
2– salts with H2SO4 used in ring test,
formation of ppt. will create turbulence in soln. therefore, brown ring complex is not formed. In such cases, above test can be modified by first adding Na2SO4 soln. Now
obtained filtrate can be used for ring test.
2. Ring test for NO3
– ion in presence of NO2
–(aq) should not be done however ring test for NO2
– (aq) ion in presence of NO3
– (aq) can be performed.
3. HNO2 exhibits better oxidising character and weak reducing character.

4. Chloride (Cl–) , Bromide (Br–) and Iodide (I–)
1. All Cl– salts are water soluble except AgCl , Hg2Cl2  , PbCl2  , CuCl (all are white ppt.)
2. All Br– salts are water soluble except AgBr (pale yellow) PbBr2  (white), Hg2Br2  (yellow), CuBr (white)
3. All I– salts are water soluble except AgI (yellow), PbI2(yellow), HgI2  (scarlet red), Hg2I2(green), BiI3  (black), CuI (white)
CuI2  (yellow)
(IMR)
.)
T
.
(R
s
spontaneou





 
 CuI + 1/2 I2
Cl¯(aq), Br¯(aq), I¯(aq)
conc.
H SO
2 4
Warm
(1)
(2)
(4)
(a)
(a) (b)
(3)
(b)
(a)
(c)
(b) (Soda Ext.)
Tests based on ppt.
reactions
Specific
tests
Chromyl
chloride
test
for
Cl¯
ion
Test
for
Br¯,
I¯
CCl
layer
4
Oxidising agent
MnO /H
4¯
+
, Cr O / H ,
H O , CaOCl , MnO
PbO , Pb O , Pb O
2 7
2 2
2 2 3 4
2– +
2 2
3
Cl¯
Cl¯(aq)
white ppt. white ppt. yellow ppt. excess
dil.NH soln.
3
NH
soln.
3
dil. conc.
conc.
NH
soln.
3
Cl¯(aq)
Br¯(aq)
Cl2
More
drop of Cl2
Excess Cl2
Few drop of
Water
Cl Water
2
for I¯
f
o
r
B
r
¯
Hot
water
very hot
water
Boiling
water
Br¯(aq)
I¯(aq) I¯(aq)
Pb(OAc) soln.
2
Reddish
Brown layer
of Br2
Brown
layer of I3¯
HIO
(colour less)
3
Violet
layer
of I2
AgNO soln.
3
KI + starch
Starch iodide
paper
Starch
greenish
yellow gas
having
suffocating
odour
Reddish
Brown vapours
having
Irritating
odour
Violet vapours
Cl2
PbCl2
Soluble Soluble Soluble [Ag(NH ) ]
3 2
+
[Ag(NH ) ]
3 2
+
No dissolution
No
dissolution
AgCl
PbBr2 AgBr
PbI2 AgI
Br2 I2
Br¯ I¯
Deep blue
colouration
Deep blue
Paper
Deep blue
colouration
MCl (solid) +K Cr O (s) +
conc.H SO (few drop)
x 2 2 7
2 4
Warm
CrO Cl
2 2
PbCrO4
Na CrO
2 4 + NaCl
(Reddish brown fumes)
NaOH
soln. (excess)
(i) CH COOH
(ii) Pb(OAc)
3
2
(Yellow ppt.)
(Soluble in dil. HNO and ex, NaOH soln.
but insoluble in CH COOH)
3
3
Cl¯(s) If we want halogen (X )
then St. Oxd. Agt. like
MnO is used and
if we want HX then
non-oxd. acid H PO
is used.
2
2
3 4
Br¯(s)
I¯(s)
HCl(white fumes with pungent odour)
SO2+HBr +Br
 
2 Reddish brown fumes)
SO2+HI +I
 
2  
Violet vapours) + S (Small Amt.)
(aq)
(yellow soln.)
Note : 1. AgCl  , PbCl2  , Hg2Cl2  , CuCl  , HgCl2(pred. covt.) PbCl4(pred. covt.) SnCl4(pred. covt.) do not give chromyl chloride test due to low concentration
of Cl– ion.
2. CH3COOH used in chromyl chloride test neutralises excess NaOH otherwise yellow ppt. of PbCrO4  is not formed.

5. SO4
2– (aq) Anion
All SO4
2– salts are water soluble except sulphate salts of Ba2+, Sr2+, Pb2+ and Hg2+
SO (aq.)
4
2–
(Soda Ext.)
(1)
BaCl2( )
sol .
n
BaSO4
(white ppt.)
(i) (ii) (iii)
No
dissolution
Ba(HSO )
4 2
(water soluble)
BaS
Coke

Hot &
conc.H SO
2 4
dil.
HCl
Sparingly
soluble
Na [Pb(OH) ]
2 4 (aq)
Soluble Sodium Plumbite
excess
NaOH
conc.
HNO3
Pb(OAc)2 sol .
n
PbSO4(white ppt)
Hg(NO )
3 2sol .
n
2HgO.HgSO4 (yellow ppt)
(Basic mercuric sulphate)
(a) Specific test (Lab test) (b) Test based on Precipitation reaction (c)
(white scales)
Note : BaSO4  , SrSO4  and PbSO4  salts are insoluble in any dil. acid at room temp. due to their low Ksp.