Cation 3 Flashcards
Group 3 cations
● Iron (Fe3+ ) Ion
● Cobalt (Co2+ ) Ion
● Nickel (Ni2+ ) Ion
● Zinc (Zn2+ ) Ion
● Manganese (Mn2+ ) Ion
● Aluminum (Al3+ ) Ion
● Chromium (Cr3+ ) Ion
The cations of Group III are precipitated in a solution containing
ammonia (NH 3)
ammonium chloride (NH4CI)
And ammonium sulfide (NH 4)2S.
group precipitate is a mixture of
sulfide and hydroxides
The high concentration of sulfide ion necessary for precipitation of Group III sulfides is obtained in an
ammoniacal solution.
This basic solution also produces the precipitation of chromium and aluminum as hydroxides in Group III.
ammoniacal solution.
These hydroxides form a soluble group when dissolved in excess KOH solution.
-> Chromium hydroxide
-> Zinc hydroxide
~> Aluminum hydroxide
These hydroxides precipitate to form an insoluble group
- Manganese hydroxide
- Iron hydroxide
- Nickel hydroxide
- Cobalt hydroxide
CENTRIFUGATE may contain
aluminum, chromium, and zinc ions.
Day 2: RESIDUE may contain
iron, cobalt, manganese, and nickel ions
confirms the presence of ALUMINUM ION.
red precipitate
confirms the presence of CHROMIUM ION.
Formation of a blue color which fades rapidly
confirms the presence of ZINC ION.
Formation of a white precipitate
Confirmatory reagent of Manganese
sodium bismuthate
confirms the presence of FERRIC ION
Appearance of deep red coloration
Reagents used to confirm presence of COBALT ION
solid NaF (Sodium fluoride)
10 drops of alcoholic NH4CNS
confirms the presence of COBALT ION.
Appearance of blue-green color at the junction of the 2 liquids
Confirmatory reagent of NICKEL ION
4 drops of dimethylglyoxime.
confirms the presence of NICKEL ION.
Formation of a red precipitate
Black
FeS
CoS
NiS
White
ZnS
Al(OH)3
Pink
MnS
Green
Cr(OH)3
Dissolve ferric, aluminum, chromic, nickelous, zinc, and manganous ions while CoS and NiS remains undissolved
Dilute HCl
(initial detection of Ni and Co ions)
Dilute HCl
**Reagent added:;
Purpose: Dissolve CoS and NiS
HNO
Separation of Group Ill into subgroups
Precipitating agents:
Sodium peroxide and potassium hydroxide
Centrifugate of aluminum
Al(H2O)2(OH)4
Centrifugate of Zinc
Zn(H2O)(OH)з
Centrifugate of Chromic
Cr(H2O)2(OH)4
Brown precipitate chemical formula
MnO(OH)2
reddish-brown precipitate chemical formula
Fe(H2O)3(OH)3
brown precipitate chemical formula
Co(H2O)з(OH)3
green gelatinous precipitate chemical formula
Ni(H2O)4(OH)2
STEP: Separation of Aluminum
Precipitating agent:
saturated ammonium chloride and dilute acetic acid
Confirmation for Aluminum ion:
Reagent:
Aluminon, thetriammonium salt of aurintricarboxylic acid, a dye
Separation of Zinc and Chromate ions (centrifugate)
Precipitating agent:
Barium Acetate
Purpose: Precipitate chromate ion as yellow precipitate but together with barium sulfate a white precipitate
Barium Acetate
Yellow precipitate chemical formula
BaCrO4
Confirmation for Chromate ion:
Reagent:
Hydrogen peroxide
(dissolve the precipitate and separate the barium sulfate)
Hydrochloric acid
Confirmatory reagent of Chromate
Hydrogen peroxide
Confirmation of Chromate
formation of blue-colored perchromate
Chemical formula of Blue- colored ion
CrO5
Confirmation for Zinc ion (centrifugate part)
Reagent:
Dilute acetic acid
Hydrogen sulfide
to neutralize ammonia leaving the zinc ions free
Dilute acetic acid
What do we get from thioacetamide
Sulfides
White precipitate formula
ZnS
to dissolve the hydroxide precipitates to make ions in free state (ionic form)
hydrochloric acid
Confirmation for Manganese ion
Reagents:
sodium bismuthate
(purple colored solution)
MnO4-
Confirmation for Ferric ion
Reagents:
ammonium thiocyanate
(reddish brown solution formula)
Fe(CNS)6^3+
Confirmation for Cobaltous ion
Reagents:
alcoholic ammonium thiocyanate
(intense blue-colored complex in the juncture of two liquids formula)
Co(CNS)4-
Confirmation for Nickelous ion
Reagents:
ammonia and dimethylglyoxime
(red precipitate formula)
NH4+
