which of the following ionic compounds would be expected to be insoluble in water?

1 Answer

• AgI, PbI2.

  As a rule, the halides (except the fluorides) of lead (II) and silver are insoluble. The reason lies in the thermodynamical changes that would result in breaking up the lattice of these salts and then hydrating the resulting ions, lead (II), silver and iodide ions are all rather large and hence do not have a highly negative enthalpy of hydration, and because of a degree of covalency they have a rather high lattice dissociation ethalpy. Though entropy would increase in this dissolution, enthalpic imbalances make it it unfavorable, so they are deemed insoluble.