Chem Lab Midterm (not part of experiment) Flashcards
I Sulfate Group includes
SO4
HCO3
PO4
Anions are grouped as
II Sulfate Group
II Halide Group
III Nitrate Group
II Halide Group includes
Cl
Br
I
S
III Nitrate Group Includes
NO3
In ______ solutions only anions of Group I are precipitated by _____
Ammoniacal
Ba
In ____ solutions only anions of group II are precipitated with _____
HNO3
Ag
Reagents of Group I Sulfate anions
NH3
BaCl2
Reagents of Group II Halide ions
HNO3
AgNO3
Reagent for Group III Nitrate ions
NO REAGENT
for all anions of this group are soluble
Anions are divided into 4 groups on basis of
Their reactions with dilute HCl
Solubilities of their Ba and Ag salts
What are the 4 divisions of anions?
I. Visible change, gas evolution and/or formation of a precipitate with dilute HCl
II. Do not react with HCl but forms precipitates with Ba ions in neutral medium
III. Do not react with either Ba ions or HCl in neutral medium
IV. Common anions which do not react with reagents of the previous groups
Anions of division I
HCO3 Silicate Sulphide Sulphite Thiosulfate
Anions of division II
Sulphate
Phosphate
Fluoride
Borate
Anions of Division III
Chloride
Bromide
Iodide
Thiocyanate
Anions of Division IV
NO3
NO2
Chlorate ions
Only anion in group I that forms a strong acid
Sulfate
It is insoluble in HCl
BaSO4
All barium salts of this group dissolve in strong acid
Group I
Test for sulfate ion
Addition of HCl and BaCl2
BaSO4 produces a _____ precipitate
White
It is stable only in basic solutions
Sulfide
Sulfide + acid =
H2S gas
When H2S gas comes in contact with moist Pb(Ac)2 filter paper it forms ________
Black Lead Sulfide
Hydrogen Sulfide has a _______ odor
Rotten egg
Sulfide ion can be destroyed by reaction with strong oxidizing agents such as ______ or ______
Sulfite ion
HNO3
All _____ salts are soluble
Nitrate
It has no precipitation test
Nitrate
Test for nitrate ions that involve reduction by ferrous ion in concentrated H2SO4
Brown-ring test
What forms the brown ring during a brown ring test?
Nitric oxide complexes with excess ferrous ion
FeNO2 = brown-ring
It is essential that an excess of _____ be used and that concentrated _____ is used in a brown ring test.
Ferrous ion
H2SO4
Nitrate test
Brown-ring test
Interferences of nitrate test
Presence of
• Bromide
• Iodide
The conc. H2SO4 will oxidize the halide ion to the free halogen, giving a false positive color.
It is a moderately weak, non- volatile acid
Phosphate
Phosphate ions precipitate by reaction with ______
Ammonium Molybdate
PO4 + ammonium molybdate =
Yellow precipitate
Mixed salt, AMMONIUM PHOSPHOMOLYBDATE
Interference in phosphate test
Presence of sulfide ions
How to get rid of sulfide ions during phosphate test
Acidify solution with HCl and then boil it
They are like sulfate ions - they are also ions of strong acids
- Chloride
- Bromide
- Iodide
- Chloride
- Bromide
- Iodide
Form _____ with Ag ion in HNO3
Insoluble salts
What color is Silver Chloride AgCl
White
What color is AgBr?
Pale yellow ( slightly soluble in ammonia solution)
What color is AgI ?
Yellow ( does not dissolve in ammonia)
These ions can be confirmed by oxidation with free Cl and generating free Br or I.
Bromide
Iodide
They are more soluble in hexane that in H2O and take on a distinctive color
Free halogens
What color is Bromide?
Reddish-brown
What color is Iodide?
Violet
It forms a weak acid, carbonic acid
Carbonate
It is not very soluble and breaks down forming H2O and CO2
Carbonic Acid
It confirms the presence of carbonate ions
Effervescence
A colorless and odorless gas released when a carbonate ion is present
Effervescence
______ + carbonate solution = effervescence
Strong acid
What group forms precipitate with Ag ions in dilute HNO3 medium?
Group III
