Answer
$Ag_2SO_4$, $Zn(OH)$, $Ba_2C_2O_4$ and $Ca_3(PO_4)_2$ are going to be more acidic in acidic solution than in pure water.
Correct answer: (b), (c), (d) and (e).
Work Step by Step
(a) $I^-$ is the conjugate base of a strong acid (HI); therefore, it is not an electrolyte.
(b), (d) and (e): $SO_4^{2-}$, $C_2O_4^{2-}$ and $PO_4^{3-}$:
These 3 anions are the conjugate bases of weak acids, $HSO_4^-$, $HC_2O_4^-$ and $HPO_4^{2-}$, respectvely.
Therefore, when a compound that contains one of them is added to an acidic solution, they will react with the hydronium ions.
According to Le Chatelier's principle, if the concentration of the anions decrease (because it is reacting), the equilibrium will favor the dissolution.
(c) The hydroxide ions will react with the hydronium ions from the acidic solution.
According to Le Chatelier's principle, if the concentration of the anions decrease (because it is reacting), the equilibrium will favor the dissolution.
