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As this page in this book says, lead(II) acetate is soluble, but does not ionize appreciably. It seems contradictory to me, since, to call a substance soluble means it has high $K_\mathrm{sp}$ (when compared with other substances with the same elemental ratios in their formula units). But how can the book say it doesn't ionize appreciably? Why call it soluble then?

EDIT: I forgot that it is wrong to say that "to call a substance soluble means it has high $K_\mathrm{sp}$", so I revised it accordingly.

Here's the picture of the actual paragraph for those who can't access the link: the picture of the actual paragraph

I recognize that this question actually reflects my inability to distinguish between dissociation and dissolution, now that I have cleared it from me, I rephrased the question to reflect my actual question. I did not erase the previous version to be able to show the reference of MEL Science's and alphonse's answers.

ACTUAL QUESTION: Why does lead(II) acetate not dissociate appreciably in water, considering that the ionic forms of acetate and lead(II) ion can be hydrated well due to the presence of partial charges in the water molecule?

Acnologia
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    It's not true that a soluble substance is one with a high $K_{\mathrm{sp}}$. $K_{\mathrm{sp}}$ describes the solubility of substances that dissociate in the solvent (see link). Not all substances dissociate on solvation. Sucrose in water is one such example. So I'd say it probably solves as a neutral molecule, but I don't know why. – Arch Stanton Sep 18 '17 at 10:26
  • Related: https://chemistry.stackexchange.com/questions/48502/why-do-some-insoluble-salts-undergo-slow-chemical-reaction-instead-of-dissociati – Nilay Ghosh Sep 18 '17 at 15:17

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A source in my native language says that lgK of PbAc2 is 4.08. It seems that lead acts as a central atom with two acetates as two-dentant ligands and two molecules of water acting as ligands too.
That means that lead acetate has its lattice ruined during dissolving, but it still forms a coordination compound.
I am not really good in coordination chemistry of lead, but I just found out that lead wants to have octahedral geometry around it, so I would assume the structure of that would be

All bonds from lead ion are not really covalent rather than coordination bonds. Mind the charges!
P. S. aq=water
P. P. S. People in the comments are saying lead is too large for acetate to be bidentate,thus I would assume acetate just forms coordination compound with lead just like a simple monodentate ligand.

MEL Science
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    Picture is wrong Pb 2+ is too big to be chelated by acetate. – Mithoron Sep 18 '17 at 14:46
  • Sure, I don't pretend the structure must be 100% true, that's just my assumption. Perhaps acetate acts as a monodentate or bridge ligand depending on the concentration. – MEL Science Sep 18 '17 at 19:23
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How can a book say? A book can say that giraffes are purple, six-legged and can fly. The better question is: what is the book saying? I don't know. A cursory glance at the Wikipedia articles (you apparently aren't aware of the need to clearly communicate the identity of the chemical you wish to discuss. I have no idea whether "lead acetate" refers to the Pb(II) or Pb(IV) compound, or something else) shows that both acetates are soluble in polar organic solvents. This indicates that both are capable of dissolution without dissociation. Confusing dissociation (which generally occurs in solvents with high dielectric strength, such as water) with dissolution (which can occur in almost any liquid) is a newbie mistake. Whether the book you refer to (your link doesn't work) is actually claiming this or something else, I don't know. You don't provide enough information and I am not familiar enough with the solution chemistry of lead to make any judgement. Lead(II) acetate is used to precipitate anions (in aqueous solution) so I'd guess that the book is simply wrong - IF - it meant to imply that there was negligible dissociation of the dissolved salt.

alphonse
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  • Ahh yes. Maybe it's my problem of distinguishing between dissociation and dissolution. This means that lead(II) acetate actually dissolves in water, but it doesn't dissociate in it. So now the real question is why lead(II) acetate does not dissociate in water? – Acnologia Sep 20 '17 at 03:12