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Multiple Choice
Determine the molar solubility of Zn(OH)₂ in a buffer solution with a pH of 11.5, given that the Ksp of Zn(OH)₂ is 4.0 x 10⁻¹⁷.
A
1.0 x 10⁻⁶ M
B
2.0 x 10⁻⁷ M
C
3.0 x 10⁻⁹ M
D
5.0 x 10⁻⁸ M
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Verified step by step guidance
1
Identify the dissolution reaction for Zn(OH)₂: Zn(OH)₂(s) ⇌ Zn²⁺(aq) + 2OH⁻(aq).
Write the expression for the solubility product constant (Ksp): Ksp = [Zn²⁺][OH⁻]².
Since the pH of the solution is 11.5, calculate the concentration of OH⁻ ions using the relation: pOH = 14 - pH. Then, [OH⁻] = 10^(-pOH).
Substitute the known values into the Ksp expression. Let the molar solubility of Zn(OH)₂ be 's'. Then, [Zn²⁺] = s and [OH⁻] = 10^(-pOH). Substitute these into the Ksp expression: 4.0 x 10⁻¹⁷ = s * (10^(-pOH))².
Solve the equation for 's' to find the molar solubility of Zn(OH)₂ in the buffer solution.