Is it possible to predict in which acid will a precipitate dissolve? Or will it dissolve in acid at all?

Question

For example, how do I know in which acid will BaCO3 dissolve? How do I know that CaC2O4 doesnt dissolve in CH3COOH without looking at a textbook?

Answer 1

The key to knowing this is to know, or look up, solubilities of different salt, compounds, etc.  So, taking your examples, BaCO₃ is certainly insoluble in water, but what Ba salt is soluble?  Well, Ba(NO₃)₂ , i.e. barium nitrate is a soluble salt.  You'd either have to know this or look it up.  Now, how do you make barium nitrate from barium carbonate?

BaCO₃ + 2HNO₃ ==> Ba(NO₃)₂ + H₂O + CO₂.  Get it?

Now for calcium oxalate, since acetic acid is a WEAK acid, it will increase the solubility of calcium oxalate only slightly, since calcium acetate is soluble.  But a strong acid would be better.  So, for example, CaC₂O₄ (calcium oxalate) would be more soluble in, say, HNO₃ because calcium nitrate is soluble and HNO₃ is a strong acid.  I hope this "sort of" makes sense.