Answer:
The compound A (BaCO₃) is the most soluble in acidic solution.
Explanation:
We analyze the dissociation of the compounds:
A) BaCO₃ ⇒ Ba⁺² + CO₃⁻²
CO₃⁻² is the conjugated base of HCO₃ acid, which is a weak acid, therefore its conjugate base is strong.
B) CuI ⇒ Cu⁺ + I⁻
I⁻ is the conjugated base of HI acid, which is a strong acid, therefore its conjugate base is weak.
C) PbCl₂ ⇒ Pb⁺² + 2 Cl⁻
Cl⁻ is the conjugated base of HCl acid, which is a strong acid, therefore its conjugate base is weak.
D) AgBr ⇒ Ag⁺ + Br⁻
Br⁻ is the conjugated base of HBr acid, which is a strong acid, therefore its conjugate base is weak.
E) NH₄NO₃ ⇒ NH₄⁺ + NO₃⁻
NO₃⁻ is the conjugated base of HNO₃ acid, which is a strong acid, therefore its conjugate base is weak.
As the medium is acidic, there is a high concentration of H₃O⁺ and the CO₃⁻² is a strong base, the concentration of CO₃⁻² decreases to form H₂CO₃ and by the Le Chatelier's principle the equilibrium of the dissociation reaction shifts to the right and increases the solubility of the salt.
