# 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

| S.No. | Experiment | Observation | Inference |
| 1. | Analysis of Group 0 (Ammonium ion NH$_4$$^+$) To a little of salt solution add a few drops of Na$_2$CO$_3$. | a. No precipitate b. A precipitate. | a.Presence of Group 0 b. Absence of Group 0. |
| 2. | Analysis of Group I (Lead ion Pb$^{2+}$) O.S. + dil. HCl | a. A white ppt soluble in hot water and reappear on cooling. b.No precipitate. | a. Presence of Group I. b. Absence of Group I |
| 3. | Analysis of Group II ( Cu$^{2+}$, Cd$^{2+}$ & As$^{3+}$) Pass the H$_2$S gas in the above soln. | a. A black ppt. b. A yellow ppt. c. No characteristic ppt. | a. Cu$^{2+}$ suspected. b. Cd$^{2+}$ or As$^{3+}$ suspected. c. Absence of Group II. |
| 4. | Analysis of Group III (Al$^{3+}$ & Fe$^{3+}$) O.S. + NH$_4$Cl + NH$_4$OH (excess) | a. A white gelatinous ppt. b. Reddish brown ppt. c. No characteristic ppt. | a. Al$^{3+}$ suspected. b. Fe$^{3+}$ suspected. c. Absence of Group III |
| 5. | Analysis of Group IV (Ni$^{2+}$, Co$^{2+}$, Zn$^{2+}$, & Mn$^{2+}$) Pass the H$_2$S gas to the above solution. | a. A black ppt. b. A white ppt. c. Flesh colored ppt. d. No characteristic ppt. | a. Ni$^{2+}$ or Co$^{2+}$ suspected. b. Zn$^{2+}$ suspected. c. Mn$^{2+}$ suspected. d. Absence of group IV. |
| 6. | Analysis of Group V (Ba$^{2+}$, Ca$^{2+}$, & Sr$^{2+}$) Heat the above content to remove the H$_2$S gas. Now add ammonium carbonate are added. | a. A white ppt. b. No white ppt. | a. Ba$^{2+}$, Ca$^{2+}$, or Sr$^{2+}$ suspected. b. Absence of Group V. |
| 7. | Analysis of group VI (Magnesium ion, Mn$^{2+}$) O.S. + NH$_4$Cl + NH$_4$OH(excess) + Na$_2$HPO$_4$ | a. A white crystalline ppt. b. No white crystalline ppt. | a. Mg$^{2+}$ suspected. b. Absence of Group VI. |

## Confirmatory test for Cations(Basic Radical)

| 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. | NH$_4$$^+$ confirmed |
| 2. | 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. | Pb$^{2+}$ confirmed |
| 3. | Copper Ion a. NH$_4$OH 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, | Cu$^{2+}$ 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 | Al$^{3+}$ 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. | Fe$^{3+}$ confirmed |
| 6. | Zinc Ion To a little of the salt soln. acetic acid and potassium ferrocyanide solns. are added | White ppt. | Zn$^{2+}$ 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 | Mn$^{2+}$ 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., NH$_4$Cl NH$_4$OH and DMG solns. are added. | a.Light green ppt soluble in excess b.Rose red ppt. | Ni$^{2+}$ confirmed |
| 9. | Cobalt Ion a.To a little of salt soln, NH$_4$OH 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 | Co$^{2+}$ confirmed |
| 10. | Barium Ion To a little of salt soln. acetic acid & potassium chromate solns. are added | A yellow ppt. | Ba$^{2+}$ confirmed |
| 11. | Calcium Ion To a little of the salt soln. NH$_4$Cl, NH$_4$OH and [(NH$_4$)$_2$C$_2$O$_4$] solns. are added. | White ppt. | Ca$^{2+}$ confirmed |
| 12. | Strontium Ion To a little of the salt soln. acetic acid and calcium sulphate solns. are added | A white ppt. | Sr$^{2+}$ confirmed |
| 13. | Magnesium Ion To a little of the salt soln. Magneson reagent and excess NaOH are added | Blue ppt. | Mg$^{2+}$ confirmed |