[yonglu1989]

Hi everyone, so i was doing a practice chemistry olympiad when i came across a question which has stumped me.
Which calcium compound is not appreciably more
soluble in 0.1 M hydrochloric acid than it is in pure
water?
(A) Limestone, CaCO3
(B) Slaked lime, Ca(OH)2
(C) Gypsum, CaSO4 • 2 H2O
(D) Hydroxyapatite, Ca5(OH)(PO4)3

The correct answer is C, but i can't seem to find an explanation as to why that is. Can someone please explain to me why the answer is C? thank you very much!
Edit: Nvm, i found the answer, i forgot my basic solubility rules.

[Burner]

The correct answer is C, but i can't seem to find an explanation as to why that is. Can someone please explain to me why the answer is D? thank you very much!

Is the answer C or D?

(A) Limestone, CaCO3
(B) Slaked lime, Ca(OH)2
(C) Gypsum, CaSO4 • 2 H2O
(D) Hydroxyapatite, Ca5(OH)(PO4)3

A and B are bases and thus undergo neutralization with acid to form soluble salts. Also, they are insoluble/sparing soluble in water.

[Vidya]

Which calcium compound is not appreciably more
soluble in 0.1 M hydrochloric acid than it is in pure
water?
(A) Limestone, CaCO3
(B) Slaked lime, Ca(OH)2
(C) Gypsum, CaSO4 • 2 H2O
(D) Hydroxyapatite, Ca5(OH)(PO4)3

In A,B and D there is a component which acts as a base and reacts with the acid like CO32- in A
OH- in B and in D OH- ...However in D SO42- are very weak bases as they are the conjugate bases of strong acid H2SO4 ...hence C shows minimum tendency of reaction with HCl and hence minimum solubility