Question

five times in the course of parts a-d of this experiment you were able to dissolve an "insoluble" compound, something that seems like a contradiction in terms, identify each of the 5 compounds and briefly explain, with the help of chemical equation, what made each of those dissolutions possible.

I believe to have found the 5 compounds and their equtions to be.

1. PbCl2(s)+4OH=[Pb(OH)4]^2-(aq)+2Cl-(aq)

2.Al(OH)3(s)+OH^-(aq)=[Al(OH)4]^-(aq)

3. Fe(OH)3(s)+3H3O(aq)+4Cl^-(aq)= [FeCl4]-(aq)+6H2O(l)

4. CaO(s)+2H3O^+(aq)=Ca^2+(aq) + 3H2O (l)

5. CuO(s) +2H3O+(aq)+ 4Cl(aq)= [CuCl4]^2-(aq) + 3H2 (l)

I know that it has to do with their KSP values and that technically every solution is soluble but due to a very small value of K we call certain solution insoluble, however I do not know how to properly answer this question, and please explain what made each of those dissolutions possible for each one, thank you.

Answer 1

This makes much sense if you know about complex formation, all those products formed (the 1-5 equations' products you posted)

if you add sufficient OH- or H+, Cl- or even NH3 ions, you will form plenty of excess with respect to the metal

then, the metal will form complex, which are soluble!

note that many times the student confuses this with the metal being in solution, which is NOT true, is a metal complex!

so, this is possible because most of copmlex are soluble in aquous ionic solution

It does NOT has to do with Ksp, but with Kf... once you added enough exces... K formation will apply