GROUP 1 CATIONS Flashcards
- (+) 4 drops of 3F HCl
The original test solution may contain Chlorides of Group I cation or _____________________
Addition of _________ causes the dissolution of the latter; thereby, leaving the chlorides of Group I cation for individual analysis.
- oxychlorides of Antimony and Bismuth
- Hydrochloric Acid
- (+) 1 drop of 3F HCl
Slight excess of ____ not only causes a more complete precipitation of the chlorides of Group I cation but also prevents the formation of ____ and ____
- HCl
- BiOCl and SbOCl
- 10 drops of cold water with 1 drop of 3F HCl
___________ may dissolve during the washing process.
The addition of ____ reduces its solubility by common-ion effect.
- Lead Chloride
- HCl
- White precipitate
(From Procedure 1) may be ______, ______, ______
PbCl2
AgCl
Hg2Cl2
ON THE INITIAL ADDITION OF 3F HYDROCHLORIC ACID
The test solution may contain a white precipitate which could either be the chlorides of Group I or the _____________
Both can be precipitated; however, the addition of concentrated ____________ can differentiate the two.
The oxychlorides of Bi and Sb will dissolve, whereas the chlorides of Group I will not.
- oxychlorides of Bismuth (Bi) and Antimony (Sb)
- Hydrochloric acid (HCl)
-
NOTE:
The reaction is ________ and the presence of oxychloride precipitate depends on the concentration of __________
BiOCl + 2H3O+ <—> Bi3+ + Cl- + 3H2O
Bismuth Oxychloride + Hydronium <—> Bismuth + Chlorine Ion + Water
- REVERSIBLE
- Hydronium ions
ON THE ADDITION OF EXCESS HYDROCHLORIC ACID
Apart from ensuring that the precipitation of Group I cation is complete, by virtue of common-ion effect, the excess prevents the formation of ________ and ________
NOTE: A large concentration of ______ or ______ should be avoided, since the amount of it in high concentration increases the solubility of the precipitated chlorides.
- AgCl + 2Cl- <—> AgCl3-
- PbCl2 + 2Cl- <—> PbCl4-
- BiOCl and SbOCl
- HCl or Chloride ion
ON THE ADDITION OF 3F AMMONIA
If the _________ is left in contact with the precipitate of _______ and _______ for an appreciable length of time, the soluble silver complex ion may react with ________.
Therefore, a small concentration of ________ may NOT give the usual test for silver ion.
- 2Hg + 2Ag(NH3)2+ <—> Hg2 2+ + 2Ag + 4NH3
Mercury Silver Diamine
Mercurous ion Silver Ammonia
- ammoniacal solution
- Mercury (Hg) and Mercuric Amidochloride (HgNH2Cl)
- metallic Hg
- Silver (Ag+)
ON THE ADDITION OF 3F NITRIC ACID
The solution must be ______ to convert the _______ to _______; otherwise, even though silver ions are present, no precipitate will form.
- acidified
- Ag(NH3)2+
- Silver Chloride (AgCl)
ON THE REMAINING PPT AFTER THE TREATMENT OF AMMONIA
If _________ are present, the residue left from the Ammonia (NH3) treatment must be _____ or _________, because of the precipitation of ____________.
Hg2Cl2 + 2NH3 <—> HgNH2Cl + Hg + NH4+ + Cl-
Mercury Chloride + Ammonia <—> Mercuric Amidochloride + Mercury + Ammonium Ion + Chloride Ion
- mercurous ions
- black or greatly discolored
- colloidal mercury
CHEMICAL REACTIONS INVOLVED IN THE SEPARATION AND IDENTIFICATION OF CATIONS OF GROUP I
- Group precipitation
- Separation and Identification of Lead Ion
- Treatment of Residue in Group I Analysis with Ammonia
- Confirmation for the presence of Silver Ion
- Identification of Mercurous Ion
- Pb2+ + 2Cl- <—> PbCl2
- Ag+ + Cl- <—> AgCl
- Hg22+ + 2Cl- <—>
Hg2Cl2
group precipitation
An incomplete separation of __________ from the group precipitate is affected with _______
PbCl2 is soluble to the extent of approximately 1g/100 ml at room temperature, and 3.34 g/ml at the temperature of boiling water.
The threefold increase insolubility is small, but sufficient to give a lead-ion concentration that can be detected with chromate ions.
- Lead Chloride (PbCl2)
- hot water
SEPARATION AND IDENTIFICATION OF LEAD ION
When a mixture of _______ and _______ is treated with _______, the _____ dissolves, leaving a BLACK residue composed of ______ and ________
- Silver Chloride (AgCl) and Mercury Chloride (HgCl2)
- Ammonia (NH3)
- AgCl
- mercury and mercuric aminochloride
AgCl + 2NH3 <—> Ag(NH3)2 + Cl-
TREATMENT OF RESIDUE IN GROUP 1 ANALYSIS WITH AMMONIA
Ammonia acts upon ________ to produce an internal ________ in which one mercurous ion is produced and the other is oxidized to the mercuric state.
__________ is WHITE and the finely divided mercury is BLACK.
The blackening of the mixture is an identification test for the mercurous ion.
- mercurous chloride
- redox reaction
- Mercuric aminochloride
Hg2Cl2 + 2NH3 <—> HgNH2Cl + Hg + NH4 + Cl-
TREATMENT OF RESIDUE IN GROUP 1 ANALYSIS WITH AMMONIA
The centrifugate from the treatment of the Group I precipitate with ammonia contains __________ and __________.
If the solution is made acidic with ________, the complex is destroyed and _____ is reprecipitated.
- Ag(NH3)2+
- Cl- ions
- nitric acid (HNO3)
- AgCl
Ag(NH3)2 + Cl- + 2H3O <—> AgCl + 2NH4 + NH4 + 2H2O
CONFIRMATION FOR THE PRESENCE OF SILVER ION
The residue from the treatment of mercurous chloride with ammonia is a mixture of ______ and ______
Although the production of BLACK mixture is sufficient to indicate the presence of the mercurous ion, additional confirmation is obtained by dissolving the mixture in _______ and testing with ________.
- Hg and HgNH2Cl
- nitric acid
- stannous chloride solution
3Hg + 2NO3- + 8H3O+ <—>
3Hg2++ 2NO + 12H2O
2HgNH2Cl + 2NO3- + 4H3O- <—> 2Hg2+ + N2 + 2NO + 2Cl- + 8H2O
IDENTIFICATION OF MERCUROUS ION
In the presence of chloride ions, the mercuric ions tend to form the slightly dissociated _________, or the _________
- mercuric chloride molecule [HgCl2]
- complex ion [HgCl4-]
- low conc of chloride ions
Hg2+ + 2Cl- <—> HgCl2 - high conc of chloride ions
HgCl2 + 2Cl- <—> HgCl4
Acid solutions containing ______ and ______ give precipitates with _______.
These precipitates may be ______, ______, ______, depending upon the relative concentrations of the reactants.
- HgCl2 and HgCl4-
- stannous ions
- white, gray, or black
2HgCl2 + SnCl4- <—> Hg2Cl2 + SnCl6-
2HgCl4 + SnCl4- <—> Hg2Cl2 + SnCl6- + 4Cl-
Further addition of _________ reduces white _______ to black, finely divided mercury.
Generally, a gray mixture of _______ and ______ is obtained.
- stannous chloride
- Hg2Cl2
- Hg2Cl2 and Hg
Hg2Cl2 + SnCl4- <—> 2Hg + SnCl6-
