Calculate the molar solubility of CuX in a 0.18 M Na2X solution, given that the solubility product constant (Ksp) for CuX is 1.27×10^-36.

• A. 2.54×10^-18 M
• B. 1.27×10^-36 M
• C. 3.56×10^-19 M
• D. 7.06×10^-36 M

Answer: (D)

Verified step by step guidance

1. Identify the chemical equilibrium involved: CuX(s) ⇌ Cu⁺(aq) + X⁻(aq). The solubility product constant (Ksp) expression for this equilibrium is Ksp = [Cu⁺][X⁻].
2. Recognize that the presence of Na2X in the solution provides a common ion, X⁻, which affects the solubility of CuX. The concentration of X⁻ from Na2X is 0.18 M.
3. Let the molar solubility of CuX be 's'. At equilibrium, the concentration of Cu⁺ will be 's' and the concentration of X⁻ will be '0.18 + s'.
4. Substitute these concentrations into the Ksp expression: Ksp = [Cu⁺][X⁻] = s(0.18 + s). Given that Ksp = 1.27×10^-36, set up the equation: 1.27×10^-36 = s(0.18 + s).
5. Assume that 's' is much smaller than 0.18 M, allowing the simplification 0.18 + s ≈ 0.18. Solve the equation 1.27×10^-36 = s(0.18) for 's' to find the molar solubility of CuX.