For AB2(s) dissolving to AB2 ⇌ A^2+ + 2 B− with Ksp = 1.0 x 10^−6, express Ksp in terms of s.

For AB2(s) dissolving to AB2 ⇌ A^2+ + 2 B− with Ksp = 1.0 x 10^−6, express Ksp in terms of s.

• A. 2 s^3
• B. 4 s^3
• C. s^3
• D. 8 s^3

Answer: (B)

The main idea is how solubility products are built from the ions produced when a solid dissolves. For AB2(s) dissociating to A^2+ and 2 B−, let the solubility be s (mol/L). Then [A^2+] = s and [B−] = 2s. The Ksp expression uses the ion concentrations: Ksp = [A^2+][B−]^2. Substituting gives Ksp = s × (2s)^2 = s × 4s^2 = 4s^3. So the Ksp in terms of s is 4s^3.

The main idea is how solubility products are built from the ions produced when a solid dissolves. For AB2(s) dissociating to A^2+ and 2 B−, let the solubility be s (mol/L). Then [A^2+] = s and [B−] = 2s. The Ksp expression uses the ion concentrations: Ksp = [A^2+][B−]^2. Substituting gives Ksp = s × (2s)^2 = s × 4s^2 = 4s^3. So the Ksp in terms of s is 4s^3.