Calculate the molar solubility of Ni(OH)₂ when buffered at pH (c) 12.0.

검증된 단계별 안내

Step 1: Write the balanced chemical equation for the dissolution of Ni(OH)₂ in water: \[ \text{Ni(OH)}_2 (s) \rightleftharpoons \text{Ni}^{2+} (aq) + 2\text{OH}^- (aq) \]

Step 2: Write the expression for the solubility product constant (K_sp) for Ni(OH)₂: \[ K_{sp} = [\text{Ni}^{2+}][\text{OH}^-]^2 \]

Step 3: Determine the concentration of OH^- ions at pH 12.0. Use the relationship between pH and pOH: \[ \text{pOH} = 14 - \text{pH} \] \[ \text{[OH]}^- = 10^{-\text{pOH}} \]

Step 4: Substitute the concentration of OH^- from Step 3 into the K_sp expression. Let the molar solubility of Ni(OH)₂ be 's', so \[ K_{sp} = s \times (\text{[OH]}^-)^2 \]

Step 5: Solve for 's', the molar solubility of Ni(OH)₂, using the known value of K_sp for Ni(OH)₂.

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주요 개념

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Molar Solubility

Molar solubility refers to the maximum amount of a solute that can dissolve in a given volume of solvent at a specific temperature, expressed in moles per liter (mol/L). It is a crucial concept in understanding how substances interact in solution, particularly for sparingly soluble compounds like Ni(OH)2. The molar solubility can be influenced by factors such as pH and the presence of other ions in solution.

pH and its Effect on Solubility

pH is a measure of the acidity or basicity of a solution, with lower values indicating acidic conditions and higher values indicating basic conditions. For metal hydroxides like Ni(OH)2, increasing the pH can enhance solubility by shifting the equilibrium of the dissolution reaction. At a pH of 12.0, the solution is basic, which can lead to increased solubility due to the formation of soluble nickel complexes.

Equilibrium and Ksp

The solubility product constant (Ksp) is an equilibrium constant that applies to the dissolution of sparingly soluble ionic compounds. It quantifies the extent to which a compound can dissolve in water, represented by the concentrations of its ions at equilibrium. For Ni(OH)2, the Ksp expression involves the concentrations of Ni²⁺ and OH⁻ ions, and understanding this relationship is essential for calculating molar solubility under specific conditions, such as a buffered pH.

Calculate the molar solubility of Ni(OH)2 when buffered at pH (c) 12.0.