Inorganic Chemistry/Qualitative Analysis/Tests for cations
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
|
a.Presence 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.
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.
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.
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.
|
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.
|
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.
add Nessler's Reagent. |
a. Pungent smelling gas producing
thick white fumes with conc. HCl
|
NH4+ confirmed |
| 2. | Lead Ion
a. To a litte of salt soln., KI soln. is added.
and Potassium chromate solns. added |
a. A yellow ppt. soluble in hot water
and reappear as golden spangle on cooling
|
Pb2+ confirmed |
| 3. | Copper Ion
a. NH4OH is added drop by drop and then in excess to a little of the salt soln.
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 |
| 4. | 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 |
| 5. | 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 |