This document summarizes qualitative cation analysis of zinc group ions. It describes how zinc, cobalt, nickel, and manganese ions react with aqueous ammonia and sodium hydroxide. Zinc ions form white zinc hydroxide precipitates with both reagents that dissolve in excess. Cobalt ions form a blue hexaammine complex with ammonia. Nickel ions form a green precipitate with ammonia that dissolves to a blue complex in excess. Manganese ions similarly form white hydroxide precipitates with both reagents. The document was presented by Patamsetti Devi Prasad on qualitative cation analysis of the zinc group.

1. QUALITATIVE
ANALYSIS OF
CATIONS OF
ZINC GROUP;
BY PATAMSETTI DEVI PRASAD
CHEMISTRY DEPARTMENT

2.  WHAT IS QUALITATIVE ANALYSIS:

3.  CATION ANALYSIS:
 Testing with various reagents gives characteristic reaction of certain , which may be a colour
change a solid formation or any other any visible changes.

4.  Zinc(II) ion reacts with aqueous ammonia to precipitate white gelatinous Zn(OH)2:
Zn2+(aq)+2NH3(aq)+2H2O(l)↽−−⇀Zn(OH)2(s)+2NH+4(aq)
Zinc Ions (Zn²⁺)
 The zinc(II) hydroxide precipitate dissolves in excess ammonia:
Zn(OH)2(s)+4NH3(aq)↽−−⇀[Zn(NH3)4]2+(aq)+2OH−(aq)

5.  Sodium hydroxide also precipitates zinc(II) hydroxide
Zn2+(aq)+2OH−(aq)↽−−⇀Zn(OH)2(s)
 The zinc(II) hydroxide precipitate also dissolves in excess hydroxide:
Zn(OH)2(s)+2OH−(aq)↽−−⇀[Zn(OH)4]2−(aq)

6.  Cobalt Ions (Co²⁺)
 Excess concentrated ammonia reacts with cobalt(II) ion to form a metal complex ion, hexaamminecobalt(II) ion:
Co2+(aq)+6NH3(aq)↽−−⇀[Co(NH3)6]2+
 Sodium hydroxide first precipitates the basic salt just described.
This basic salt is insoluble in excess sodium hydroxide,but is soluble in acids.
When heated, the basic salt hydrolyzes to form Co(OH)2Co(OH)2.
cobalt(II) hydroxide is slowly oxidized by atmospheric oxygen to form brown Co(OH)3Co(OH)3.

7. Nickel Ions (Ni²⁺)
Aqueous ammonia precipitates green gelatinous Ni(OH)2:
Ni2+(aq)+2NH3(aq)+2H2O(l)↽−−⇀Ni(OH)2(s)+2NH+4(aq)
 The nickel(II) hydroxide precipitate dissolves in excess ammonia to form a blue complex ion:
Ni(OH)2(s)+6NH3(aq)↽−−⇀[Ni(NH3)6]2+(aq)+2OH−(aq)

8.  Sodium hydroxide also precipitates nickel(II) hydroxide:
Ni2+(aq)+2OH−(aq)↽−−⇀Ni(OH)2(s)

9.  Manganese Ions (Mn²⁺)
 Addition of aqueous ammonia precipitates white Mn(OH)2Mn(OH)2:
Mn2+(aq)+2NH3(aq)+2H2O(l)↽−−⇀Mn(OH)2(s)+2NH+4(aq)
 Sodium hydroxide precipitates manganese(II) hydroxide:
Mn2+(aq)+2OH−(aq)↽−−⇀Mn(OH)2(s)

10. PRESENTATION BY PATAMSETTI DEVI PRASAD…………