Which of the following compounds is more soluble in a 0.1 M HCl solution than in pure water?

Question

	MgF2
	AgI
	SrSO4
	Ba(NO3)2

Answer 1

MgF₂ would be more soluble in HCl because the anion (F-) will form a weak acid (HF) and according to Le Chatelier, this will increase the solubility as seen below:

MgF2(s) <==> Mg²⁺(aq) + 2F^-(aq) if F^- forms HF, this doesn't readily dissociate so reaction goes to right.

For the other salts, the anions will all form strong acids and will not increase their solubility in strong acid.