Analyzing Group I Cations (Silver Group)

Group I Cations (Silver Group)

• The group includes lead, silver, and mercurous, with their respective ions: $Pb^{2+}$, $Ag^{+}$, and $Hg_2^{2+}$

Steps of Analysis

• Precipitation is the first step of analysis, using cold dilute $HCl$ as the group reagent
• The group reagent $HCl$ precipitates the ions as chlorides, with the following formulas: $AgCl$, $PbCl_2$, and $Hg_2Cl_2$, resulting in a white precipitate
• $HCl$ is preferred over $NH_4Cl$ because it prevents the formation of insoluble bismuth oxychloride precipitate
• A slight excess of $HCl$ should be added to ensure complete precipitation and prevent peptization of the insoluble chlorides
• The chemical equation for the precipitation of $PbCl_2$ is: $Pb^{2+} + 2Cl^- + H_2O \rightarrow PbCl_2 \downarrow$