The group II reagent in the cation analysis is the dil.HCl + H₂S. The role of dil.HCl is

To decrease  $\left[S^{2-}\right]$and so increase the ionic product to exceed the ${\mathrm{K}}_{\mathrm{Sp}}$  of  group IV sulphides and prevent their precipitation.

To dissolve group II metal sulphides in acid medium

To decrease $\left[{\mathrm{S}}^{2-}\right]$ concentration so that the  ionic product of  only  group II sulphides exceed  their K_sp  values