Ion separation Flashcards
Group 1 cations
Ag2+, Pb2+, Hg2+
Group 2 cations
As3+, Bi3+, Cd2+, Cu2+, Hg2+, Sb3+, Sn2+
Group 3 cations
Cr3+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Zn2+, Al3+
Group 4 cations
Mg2+, Ca2+, Sr2+, Ba2+
Group 5 cations
Li+, Na+, K+, Rb+, Cs+, NH4+
When HCl is added
Precipitates group 1 cations as insoluble chlorides.
AgCl, PbCl2, Hg2Cl2
When H2S is added
H2S is a colorless inflammable gas having a rotten egg smell.
Group 2 cations will be precipitated as acid insoluble sulfides.
As2S3, Bi2S3, CdS, CuS, HgS, Sb2S3, SnS
Sb
Antimony
Bi
Bismuth
Add NaOH, NH3 OR (NH4)2S
Group 3 cations will be precipitated as base insoluble sulfides or hydroxides.
Cr(OH)3, MnS, FeS, CoS, NiS, ZnS, Al(OH)3
Add Na2CO3 or (NH4)2HPO4
Precipitates group 4 cations as insoluble carbonates or phosphates.
MgCO3, CaCO3, SrCO3, BaCO3
Procedure for obtaining group1 chlorides as precipitates
Cold dilluted HCl is added to the solution
Process of obtaining group 2 sulfides as precipitates
The filtrate from obtaining group 1 precipitates is still acidic.
H2S is passed through the solution
Process of obtaining group 3 hydroxides and sulfides as precipitates
Add NH4Cl and NH4OH. Then pass H2S through the solution
Process of obtaining group 4 carbonates as precipitates
Boil the filtrate obtained to repel H2S. Then add little amount of NH4Cl and NH40H in excess. Heat the solution and add (NH4)2CO3 solution.
Black sulfides
Bi2S3, Pbs, CuS, HgS, CoS, NiS
Yellow sulfides
CdS, As2S3, SnS2
Sb2S3
Orange
SnS
Brown
MnS
Pink
ZnS
White
Chlorides formed by group 1 cations
All are white in color.
Colour of Cr 3+ in acidic medium
Green
Will Pb2+ form a precipitate upon addition of hot conc. HCl
It will not
Pb2+ will form complex ion chlorides with hot conc.HCl
