AP Chemistrymediummcq1 pt
The molar solubility of Mg(OH)₂ is 1.4 × 10⁻⁴ M in pure water. What is the Ksp of Mg(OH)₂?
A.2.7 × 10⁻¹²
B.1.1 × 10⁻¹¹
C.2.0 × 10⁻⁸
D.1.4 × 10⁻⁴
Explanation
Core Concept
Each formula unit releases one Mg²⁺ and two OH⁻ ions, so saturation gives [Mg²⁺] = s and [OH⁻] = 2s. The solubility product becomes Ksp = [Mg²⁺][OH⁻]² = (s)(2s)² = 4s³. Inserting s = 1.4 × 10⁻⁴ M produces Ksp = 4(2.7 × 10⁻¹²), about 1.1 × 10⁻¹¹. The coefficient 2 matters twice: it doubles the hydroxide level and then gets squared inside the expression.
Correct Answer
B1.1 × 10⁻¹¹
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