EK1001 Chemistry:Adding HCl increases solubility of CaF2?

[UIUCstudent]

So this concerns question 546 and 547 of the 1001 gen chem EK book.

So 0.1M HCl is added to a saturated solution of CaF2. EK says that the acid increases the solubility of CaF2. The explanation is because the chloride ions are spectator ions, leaving protons to push the reaction to the right.

Which leaves me confused..

It then goes on in the next question where it asks what happens if more CaF2 is added to the solution. Answer: A precipitate does not form because when the acid was added, the dissociation equilibrium shifted to the right allowing room for more calcium.

So is this usually the case where adding acidic HCl increases the solubility of neutral salt compound (not sure if CaF2 is considered basic, neutral, or acidic)?

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[WhiteWashed]

So this concerns question 546 and 547 of the 1001 gen chem EK book.

So 0.1M HCl is added to a saturated solution of CaF2. EK says that the acid increases the solubility of CaF2. The explanation is because the chloride ions are spectator ions, leaving protons to push the reaction to the right.

Which leaves me confused..

It then goes on in the next question where it asks what happens if more CaF2 is added to the solution. Answer: A precipitate does not form because when the acid was added, the dissociation equilibrium shifted to the right allowing room for more calcium.

So is this usually the case where adding acidic HCl increases the solubility of neutral salt compound (not sure if CaF2 is considered basic, neutral, or acidic)?

The addition of HCl leaves H+ and Cl- ions in the solution. F- is a weak acid, so it wants to grab onto protons to form HF. the formation of HF effectively lowers the concentration of F- in solution, allowing more CaF2 to go into solution...because there are a lower amount of F- ions.

Makes sense?

 

[UIUCstudent]

Oh its a complex equilibrium. I wish EK said that in the explanation. Thanks!

 

[Rabolisk]

Just to be sure, HF is a weak acid, and F- is a weak base.

 

[chemtopper]

CaF2 is a basic salt
CaF2-----> Ca2+ + 2F-
2F- +H2O -----> 2HF + 2OH-(basic )