Answer is:
H2S (alkaline)
Explanation:
In presence of NH4OH, dissociation of H2S is remarkably high, so increases the solubility product of group IV sulphides.
Answer is:
Hot dilute HCl solution
Explanation:
Both Pb and Ag form white ppt. of their chlorides. But PbCl2 is soluble in hot water while AgCl is not.