GROUP 2 Flashcards
qualities
Group II-A
basic so, they are insoluble in KOH
qualities
Group II-B
acidic so, they are soluble in KOH
what are the chemicals in
Group II-A
PbS, HgS, Bi2S3 , CuS, CdS
what are the chemicals in
Group II-B
AsS3 -3
SnS3 -3
SbS3 -2
main test
Cu + HCL + thioacetamide
black ppt
Copper sulphide
Confirmatory tests
Cu + Dil. Ammonia
[Cu(NH3)4]2+
Blue Color
Copper amine complex
Cu + Pot.Ferrocyanide
Cu2[Fe(CN)6]
Chocolate-brown ppt
Copper ferrocyanide
main test
Bi + 1ml HCl + thioacetamide
heat in water bath
Bi2S3
Brown ppt
Bismuth sulphide
Confirmatory tests
Bi + Dil. Ammonia
Bi(OH)2 NO3
White ppt
Bismuth oxynitrate
Bi + Dil.HCl + Large volume of water
BiOCl
White ppt
Bismuth oxychloride
Identification of Cu+2
Cu2+ + H2S
Copper reacts with Hydrogen sulphide
CuS + H+
Black ppt
Copper sulphide
Identification of Bi+3
2Bi3+ + 3H2S
Bismuth reacts with Hydrogen sulphide
Bi2 S3 + 6H+
Brown ppt
Bismuth sulphide
Identification of Cd+2
Addition of small amounts of NaCN, then addition of thioacetamide and heat
CbS
Canary yellow ppt
Adjusting the acidity: Why and how?
if the solution is too strongly acidic:
lead, cadmium and tin may be incompletely precipitated; due to the formation of stable complexes.
Adjusting the acidity: Why and how?
If the solution too weakly acidic:
group IV sulphides (NiS, CoS and ZnS) may be precipitated.
