which of the following could dissolve a precipitate of CaC2O4 in a saturated solution of CaC2O4?

Question

A.NaOH
B.CaC2O4
C.H2C2O4
D.Ca(NO3)2

i know it is A, but why??

Answer 1

Oh reacts with Ca which decreases [Ca] and pushes reaction right

CaC2O4<>Ca+C2O4

Answer 2

I think this question has something to do with common ion effect, which is: the presence of a common ion in a solution will lower the solubility of a salt. Choices B, C, and D all contain common ions as the salt CaC2O4.