Consider the compounds with the generic formulas listed and their corresponding molar solubilities in pure water. Which compound has the smallest value of Ksp? a. AX; molar solubility = 1.35⨉10^-4 M b. AX₂; molar solubility = 2.25⨉10^-4 M c. A₂X; molar solubility = 1.75⨉10^-4 M

Verified step by step guidance

1. Write the dissolution reactions for each compound: AX dissolves as AX(s) → A+(aq) + X-(aq), AX2 dissolves as AX2(s) → A+(aq) + 2X-(aq), and A2X dissolves as A2X(s) → 2A+(aq) + X-(aq).
2. Write the expression for the solubility product constant (Ksp) for each compound based on their dissolution reactions. For AX, Ksp = [A+][X-]; for AX2, Ksp = [A+][X-]^2; for A2X, Ksp = [A+]^2[X-].
3. Substitute the molar solubility values into the Ksp expressions. For AX, use s = 1.35 * 10^-4 M; for AX2, use s = 2.25 * 10^-4 M; for A2X, use s = 1.75 * 10^-4 M.
4. Calculate the Ksp values using the substituted values. Remember that for AX2 and A2X, the concentration of X- and A+ will be multiples of the molar solubility due to the stoichiometry of the dissolution reactions.
5. Compare the calculated Ksp values to determine which compound has the smallest Ksp.

Key Concepts

Solubility Product Constant (Ksp)

The solubility product constant (Ksp) is an equilibrium constant that applies to the solubility of ionic compounds. It quantifies the extent to which a compound can dissolve in water, represented by the concentrations of its ions at equilibrium. A lower Ksp value indicates a less soluble compound, making it essential for comparing the solubility of different compounds.

Molar Solubility

Molar solubility refers to the maximum concentration of a solute that can dissolve in a given volume of solvent at equilibrium. It is typically expressed in moles per liter (M). Understanding molar solubility is crucial for calculating Ksp, as it directly influences the concentrations of ions in solution, which are used to determine the Ksp value for a compound.

Dissociation of Ionic Compounds

Ionic compounds dissociate into their constituent ions when they dissolve in water. The stoichiometry of this dissociation affects the relationship between molar solubility and Ksp. For example, a compound that dissociates into more ions will have a higher Ksp for the same molar solubility compared to a compound that dissociates into fewer ions, making it important to consider the formula of each compound when comparing their Ksp values.