Cations I

Qualitative Analysis Chapter 12

Hg2 +2

Pb +2

Ag +

Group I Cations

Group I Cations

Group of cations whose chlorides are relatively insoluble in dilute acids.

1 x 10-4

Solubility product of PbCl2

2 x 10-18

Solubility product of Hg2Cl2

1\.56 x 10-10

Solubility product of AgCl

0\.04 F

Solubility of PbCl2

7\.5 x 10-7 F

Solubility of Hg2Cl2

1\.3 x 10-5 F

Solubility of AgCl

Common-Ion Effect

refers to the decrease in solubility of an ionic precipitate by the addition to the solution of a soluble compound with an ion in common with the precipitate

Incompletely precipitated

Due to solubility, silver chloride and mercurous chloride are almost completely precipitated; however, lead chloride is ____

Increase in solubility

Lead chloride undergoes an _________ in hot water

0\.673g/100mL

solubility of pbcl2 in water at 0 degrees Celsius

3\.34g/100mL

solubility of pbcl2 in water at 100 degrees Celsius

White Precipitate

A portion of the undissolved PbCl2 may remain as a ____ that might cause confusion in the analysis of the silver and mercurous chlorides

Ammonia

Silver is separated from mercurous chloride through its solubility in ____

Ag(NH3)2 +

Silver Ammonia Complex Ion

Very Large

If the amount of AgCl is ____, some of it may not be dissolved in Ammonia water

Ammonia Water

Serves as a medium for the auto-redox reaction of Hg2Cl2

Mercury

Mercuric Aminochloride

Products of the auto-redox reaction of Hg2Cl2 that are both insoluble.

3F HCl

Group Precipitating Agent for Cations I

Yellow ppt

Confirmatory Result for Lead Ion

K2CrO4

Confirmatory Reagent for Lead Ion

3F HNO3

Confirmatory Reagent for Silver Ion

White ppt

Confirmatory Result for Silver Ion

White/Gray ppt

Confirmatory Result for Mercurous Ion

SnCl2 Solution

Confirmatory Reagent for Mercurous Ion

Precipitation with dilute HCl

PbCl2 is separated by leaching solution with hot water

Separation of AgCl from Hg2Cl2 with ammonia water

Three principal steps of the procedures of the analysis of Group I Cations

Oxychlorides of Sb and Bi

A white precipitate from the start may indicate the presence of group i cations and the ________

HCl

SbOCl and BiOCl are soluble in ___ while group i cations are not.

Solubilities

A high concentration of HCl is to be avoided since it increases the ___ of the precipitated chlorides through the formation of the soluble complex ions

Dissolve

PbCl2 may ____ appreciably during the washing process

Lead Chloride

Fairly soluble in hot water but reprecipitates if the solution is allowed to cool.

Metallic Mercury

If the ammoniacal solution is left in contact with the precipitate of Hg and HgNH2Cl, the soluble silver complex ion react with ______

Ag(NH3)2 +

The solution must be acid to convert ____ to AgCl

Colloidal Mercury

If mercurous ions are present, the residue left from the ammonia treatment must be black or greatly discolored because of the precipitation of ______.

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Group ppt rxn

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Identification of Lead Ion

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Identification of Silver Ion

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Identification of Mercurous Ion