Inorganic Chemistry/Qualitative Analysis/Tests for cations

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Please note that the groups of cations mentioned/discussed here do not refer to the groups of the periodic table! The various cations have been arranged into several groups for the purpose of qualitative analysis and these are the groups that we are talking about.

Qualitative Analysis for Cations[edit]

S.No. Experiment Observation Inference
1 Analysis of Group 0

(Ammonium ion NH4+)


To a little of salt solution add a few

drops of Na2CO3.

a. No precipitate


b. A precipitate.

a.Presence of Group 0


b. Absence of Group 0.

2 Analysis of Group I

(Lead ion Pb2+)

O.S. + dil. HCl

a. A white ppt soluble in hot water

and reappear on cooling.

b.No precipitate.

a. Presence of Group I.


b. Absence of Group I

3 Analysis of Group II

( Cu2+, Cd2+ & As3+)

Pass the H2S gas in the above soln.

a. A black ppt.



b. A yellow ppt.

c. No characteristic ppt.

a. Cu2+ suspected.


b. Cd2+ or As3+ suspected.

c. Absence of Group II.

4 Analysis of Group III

(Al3+ & Fe3+)

O.S. + NH4Cl + NH4OH (excess)

a. A white gelatinous ppt.



b. Reddish brown ppt.

c. No characteristic ppt.

a. Al3+ suspected.


b. Fe3+ suspected.

c. Absence of Group III

5 Analysis of Group IV

(Ni2+, Co2+, Zn2+, & Mn2+)

Pass the H2S gas to the above solution.

a. A black ppt.



b. A white ppt.


c. Flesh colored ppt.

d. No characteristic ppt.

a. Ni2+ or Co2+ suspected.


b. Zn2+ suspected.


c. Mn2+ suspected.

d. Absence of group IV.

6 Analysis of Group V

(Ba2+, Ca2+, & Sr2+)


Heat the above content to remove the H2S

gas. Now add ammonium carbonate are

added.

a. A white ppt.


b. No white ppt.

a. Ba2+, Ca2+, or Sr2+ suspected.

b. Absence of Group V.

7 Analysis of group VI

(Magnesium ion, Mn2+)

O.S. + NH4Cl + NH4OH(excess) + Na2HPO4

a. A white crystalline ppt.


b. No white crystalline ppt.

a. Mg2+ suspected.

b. Absence of Group VI.

Confirmatory test for Cations(Basic Radical)[edit]

S. No. Experiment Observation Inference
1 Ammonium Ion

a.A little of salt soln. is warmed

with NaOH soln.


b. To a very little of salt soln.,

add Nessler's Reagent.

a. Pungent smelling gas producing

thick white fumes with conc. HCl


b. A brown ppt.

NH4+ confirmed
Lead Ion

a. To a litte of salt soln., KI soln. is

added.


b. To a little of salt soln., acetic acid

and Potassium chromate solns.

added

a. A yellow ppt. soluble in hot water

and reappear as golden spangle

on cooling


b. A yellow ppt.

Pb2+ confirmed
Copper Ion

a. NH4OH is added drop by drop

and then in excess to a little of the

salt soln.


b. To a little of the salt soln., acetic

acid and potassium ferrocyanide

solns. are added.

a. A light blue ppt. dissolved in excess

to form deep blue soln.


b. A chocolate brown ppt,

Cu2+ confirmed
Aluminium Ion

To a little of the salt soln. NaOH is

added first drop by drop and then

in excess.

Gelatinous white ppt. soluble in excess Al3+ confirmed
Ferric ion

To a little of the salt soln. NaOH is

added first drop by drop and then

in excess.

Reddish brown ppt. Fe3+ confirmed
6. Zinc Ion

To a little of the salt soln. acetic acid

and potassium ferrocyanide solns.

are added

White ppt. Zn2+ confirmed
7. Manganese Ion

To a little of the salt soln. NaOH is

added first drop by drop and then

in excess.

White ppt. soluble in excess and turns

brown in air

Mn2+ confirmed
8. Nickel Ion

a.To a little of the salt soln. NaOH is

added first drop by drop and then

in excess.

b. To a little of the salt soln., NH4Cl

NH4OH and DMG solns. are

added.

a.Light green ppt soluble in excess


b.Rose red ppt.

Ni2+ confirmed
9 Cobalt Ion

a.To a little of salt soln, NH4OH and

potassium ferrocyanide solns. are

added.

b.To a little of the salt soln.

ammonium thiocyanate is added

a.A reddish brown ppt.


b. Blue Coloration

Co2+ confirmed
10. Barium Ion

To a little of salt soln. acetic acid &

potassium chromate solns. are added

A yellow ppt. Ba2+ confirmed
11. Calcium Ion

To a little of the salt soln. NH4Cl,

NH4OH and [(NH4)2C2O4] solns.

are added.

White ppt. Ca2+ confirmed
12. Strontium Ion

To a little of the salt soln. acetic acid

and calcium sulphate solns. are added

A white ppt. Sr2+ confirmed
13. Magnesium Ion

To a little of the salt soln. Magneson

reagent and excess NaOH are added

Blue ppt. Mg2+ confirmed