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The book I am using is "General Chemistry: Principles and Modern Applications by Ralph H. Petrucci. On page 158 the Solubility Guidelines for Common Ionic Solids is given. Rule 3 states that, "Salts of silver, lead, and mercury(I) are insoluble, however, my book states that $\ce{AgClO4}$ is soluble. Can someone explain?

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  • $\begingroup$ As you say, these are only guidelines, and nothing is absolute. $\endgroup$ – Dissenter Oct 18 '14 at 17:23
  • $\begingroup$ Silver perchlorate is voluble. $\endgroup$ – Abel Friedman Oct 18 '14 at 19:52
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Different guidelines will say slightly different things to convey the same idea. Many I've seen don't explicitly mention silver, but still produce the same result for most compounds. I don't have that book but if it's anything like these, there's probably another line that says salts of anions like nitrate and chlorate are soluble.

This table is worded a bit better to make the possibility of exceptions more explicit:

  1. Salts containing Group I elements are soluble ($\ce{Li+, Na+, K+, Cs+, Rb+}$). Exceptions to this rule are rare. Salts containing the ammonium ion ($\ce{NH4+}$) are also soluble.
  2. Salts containing nitrate ion ($\ce{NO3-}$) are generally soluble.
  3. Salts containing $\ce{Cl^-, Br^-, I^-}$ are generally soluble. Important exceptions to this rule are halide salts of $\ce{Ag^+, Pb^{2+}}$, and $\ce{(Hg2)^{2+}}$. Thus, $\ce{AgCl, PbBr2}$, and $\ce{Hg2Cl2}$ are all insoluble.
  4. Most silver salts are insoluble. $\ce{AgNO3}$ and $\ce{Ag(C2H3O2)}$ are common soluble salts of silver; virtually anything else is insoluble.
  5. Most sulfate salts are soluble. Important exceptions to this rule include $\ce{BaSO4, PbSO4, Ag2SO4}$ and $\ce{SrSO4}$ .
  6. Most hydroxide salts are only slightly soluble. Hydroxide salts of Group I elements are soluble. Hydroxide salts of Group II elements ($\ce{Ca, Sr,Ba}$) are slightly soluble. Hydroxide salts of transition metals and $\ce{Al^{3+}}$ are insoluble. Thus, $\ce{Fe(OH)3, Al(OH)3, Co(OH)2}$ are not soluble.
  7. Most sulfides of transition metals are highly insoluble. Thus, $\ce{CdS, FeS, ZnS, Ag2S}$ are all insoluble. Arsenic, antimony, bismuth, and lead sulfides are also insoluble.
  8. Carbonates are frequently insoluble. Group II carbonates ($\ce{Ca, Sr, Ba}$) are insoluble. Some other insoluble carbonates include $\ce{FeCO3}$ and $\ce{PbCO3}$.
  9. Chromates are frequently insoluble. Examples: $\ce{PbCrO4, BaCrO4}$
  10. Phosphates are frequently insoluble. Examples: $\ce{Ca3(PO4)2, Ag3PO4}$
  11. Fluorides are frequently insoluble. Examples: $\ce{BaF2, MgF2 PbF2}$.
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  • $\begingroup$ Since the author has made the table freely available, I incorporated it into the answer. $\endgroup$ – jonsca Oct 18 '14 at 20:29

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