Match List-I with List-II
 

List-I (Ion)	List-II (Group Number in Cation Analysis)
A. Co²⁺	I. Group-I
B. Mg²⁺	II. Group-III
C. Pb²⁺	III. Group-IV
D. Al³⁺	IV. Group-VI

Choose the correct answer from the options given below:

CONCEPT:

Group Analysis of Cations

• The classification of cations into different groups is based on their solubility and behavior in qualitative analysis.
• Group I cations form insoluble chlorides when treated with dilute hydrochloric acid.
• Group II cations form insoluble sulfides when treated with hydrogen sulfide in an acidic medium.
• Group III cations form insoluble hydroxides when treated with ammonium hydroxide.
• Group IV cations form insoluble phosphates when treated with ammonium molybdate in an acidic medium.
• Group V cations do not form precipitates under normal conditions and are analyzed last.

Match the Group with their respective Cations and Group Reagents.

EXPLANATION:

• Co²⁺ (Cobalt ion): This ion is typically classified as Group-IV in cation analysis because it forms hydroxides when treated with ammonium hydroxide.
• Mg²⁺ (Magnesium ion): This ion belongs to Group-VI as it forms sulfides in the presence of hydrogen sulfide in an acidic medium.
• Pb²⁺ (Lead ion): This ion is usually classified as Group-I because it forms phosphates when treated with ammonium molybdate in an acidic medium.
• Al³⁺ (Aluminum ion): This ion is classified as Group-III because it forms insoluble chlorides in the presence of dilute hydrochloric acid.

Therefore, the correct answer is A-III, B-IV, C-I, D-II