Test For Silver(I) ion

1.      Dilute HCl test:

When dilute HCl or any soluble chloride is added, a white ppt is obtained, which dissolves in ammonium hydroxide solution but reappears on adding nitric acid.

Ag+ + Cl → AgCl↓

AgCl + 2NH3 → [Ag(NH3)2]+ + Cl

Conc HCl does not give any ppt due to [AgCl2] formation.

AgCl + Cl → [AgCl2]

2.      Hydrogen sulphide test:

When hydrogen sulphide gas is passed or saturated aqueous solution is added, a black ppt is obtained, which dissolves in hot and conc nitric acid to yield a white ppt.

2Ag+ +  H2S→ Ag2S↓ + 2H+

3Ag2S + 8HNO3 → S↓ + 2NO↑ + 6Ag+ + 6NO3 + 4H2O

3.      Ammonia test:

When ammonium hydroxide solution is added, a brown ppt is obtained. The ppt dissolves in excess of the reagent.

2Ag+ + 2NH3 + H2O → Ag2O ↓+ 2NH4+

Ag2O + 4NH3 + H2O → 2[Ag(NH3)2]+ + 2OH

The solution should be disposed of quickly, as Ag3N is formed due to decomposition, which explodes readily.

4.      Sodium hydroxide test:

When sodium hydroxide solution is added, a brown ppt is obtained.

2Ag + + 2OH → Ag2O ↓ + H2O

5.      Potassium iodide test:

When potassium iodide solution is added, a yellow ppt is obtained.

Ag+ + I → AgI↓

6.      Potassium chromate test:

When potassium chromate solution is added, a red ppt is obtained. The ppt dissolves in acidic medium (turns orange) and ammonia solution.

2Ag+ + CrO42- → Ag2CrO4

Ag2CrO4 + 2H+ →4Ag+ + Cr2O72- + H2O

Ag2CrO4 + 4NH3 → 2[Ag(NH3)2]+ + CrO42-

7.      Sodium carbonate test:

When sodium carbonate solution is added, a yellow-white ppt is obtained. On heating, the ppt decomposes to produce a brown ppt.

2Ag+ +CO32- →Ag2CO3

Ag2CO3→ Ag2O ↓ + CO2

8.      Disodium hydrogen phosphate test:

When disodium hydrogen phosphate solution is added, a yellow ppt is obtained. The ppt dissolves in nitric acid and ammonia solution.

3Ag+ + HPO42- → Ag3PO4↓ + H+

Ag3PO4↓ + H+→ 3Ag+ + HPO42-

Ag3PO4 + 6NH3 → 3[Ag(NH3)2]+ + PO43-

9.      Rhodanine test:

The silver solution is treated with nitric acid followed by 1 drop of p-dimethylaminobenzylidene-rhodanine solution, a reddish-violet ppt is formed.