Chemistry

The key is recognizing that molar solubility (how many moles dissolve) differs from ion concentration depending on the salt's formula. For XY, dissolving $1.5\times10^{-4}\,\text{M}$ produces equal concentrations of X⁺ and Y⁻, which you can use to verify the given $K_{sp}$. For X₃Y₂, the same molar solubility produces different ion concentrations—three times as many X⁺ ions and twice as many Y⁻ ions—so you must account for these stoichiometric coefficients when calculating $K_{sp}$.

The key is recognizing that molar solubility (how many moles dissolve) differs from ion concentration depending on the salt's formula. For XY, dissolving $1.5\times10^{-4}\,\text{M}$ produces equal concentrations of X⁺ and Y⁻, which you can use to verify the given $K_{sp}$. For X₃Y₂, the same molar solubility produces different ion concentrations—three times as many X⁺ ions and twice as many Y⁻ ions—so you must account for these stoichiometric coefficients when calculating $K_{sp}$.