Which of the following salts will be substantially more soluble in acidic solution than in pure water: (a) ZnCO3, (b) ZnS, (c) BiI3, (d) AgCN, (e) Ba3(PO4)2?

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Identify the salts that contain anions which can react with H+ ions in an acidic solution. These anions typically come from weak acids.

Consider the solubility equilibrium of each salt in water and how the presence of H+ ions can shift this equilibrium by reacting with the anion.

For each salt, write the dissolution reaction and the possible reaction of the anion with H+ ions. For example, for ZnCO3, the dissolution reaction is ZnCO3(s) ⇌ Zn²⁺(aq) + CO₃²⁻(aq), and CO₃²⁻ can react with H+ to form HCO₃⁻ or H₂CO₃.

Evaluate which anions form weak acids upon reacting with H+ ions, as this will increase the solubility of the salt in acidic solution. For instance, CO₃²⁻ forms H₂CO₃, a weak acid, which increases the solubility of ZnCO3 in acidic solution.

Determine which salts have anions that form weak acids, making them more soluble in acidic solutions compared to pure water.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Solubility Product Constant (Ksp)

The solubility product constant (Ksp) is an equilibrium constant that applies to the solubility of sparingly soluble ionic compounds. It quantifies the extent to which a salt can dissolve in water, represented by the product of the molar concentrations of its constituent ions, each raised to the power of their coefficients in the balanced dissolution equation. Understanding Ksp helps predict how changes in conditions, such as pH, affect solubility.

Common Ion Effect

The common ion effect refers to the decrease in solubility of a salt when a common ion is added to the solution. This phenomenon occurs because the addition of a common ion shifts the equilibrium position of the dissolution reaction, according to Le Chatelier's principle, leading to reduced ionization of the salt. In acidic solutions, the presence of H+ ions can affect the solubility of certain salts that contain basic anions.

Acid-Base Reactions and Salt Solubility

The solubility of certain salts can be significantly influenced by the pH of the solution, particularly for salts containing basic anions. In acidic solutions, anions that can react with H+ ions, such as carbonate (CO3^2-) or sulfide (S^2-), may form weak acids, thus increasing the solubility of the salt. This principle is crucial for understanding which salts will dissolve more readily in acidic conditions compared to neutral water.

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Acid-Base Reaction

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Textbook Question

From the value of Kf listed in Table 17.1, calculate the concentration of Ni2 +1aq2 and Ni1NH326 2+ that are present at equilibrium after dissolving 1.25 g NiCl2 in 100.0 mL of 0.20 M NH31aq2.