Question

Explain why in the precipitation of group I cations as chlorides, it is preferable to add a slightly more quantity of dil HCl than required.

Answer 1

The slight excess of dil HCl not only causes complete precipitation of group I chlorides but this also prevents the formation of white ppt of BiOCl and SbOCl with first group chlorides
`BiOCl +2HCl hArr underset("(Soluble)")(BiCl_(3))+H_(2)O`
`SbOCl+2HCl hArr underset("(Soluble)")(SbCl_(3))+H_(2)O`