Refer to the Ksp value from Table 17.2 to calculate the solubility of iron(II) hydroxide in pure water in grams per 100 mL of solution.

Name: Chemistry: A Molecular Approach
Author: Tro
ISBN: 9780134112831

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Identify the chemical formula for iron(II) hydroxide, which is Fe(OH)_2.

Write the dissolution equation for Fe(OH)_2: Fe(OH)_2 (s) \(\rightleftharpoons\) Fe^{2+} (aq) + 2OH^{-} (aq).

Express the solubility product constant (K_{sp}) for Fe(OH)_2: K_{sp} = [Fe^{2+}][OH^{-}]^2.

Let the solubility of Fe(OH)_2 be 's' mol/L. Then, [Fe^{2+}] = s and [OH^{-}] = 2s.

Substitute these expressions into the K_{sp} equation and solve for 's'. Convert the solubility from mol/L to grams per 100 mL using the molar mass of Fe(OH)_2.

주요 개념

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Solubility Product Constant (Ksp)

The solubility product constant (Ksp) is an equilibrium constant that applies to the solubility of sparingly soluble ionic compounds. It represents the maximum concentration of ions in a saturated solution at a given temperature. For iron(II) hydroxide, Ksp can be used to determine the solubility by setting up an equilibrium expression based on the dissociation of the compound into its constituent ions.

Dissociation of Iron(II) Hydroxide

Iron(II) hydroxide (Fe(OH)2) dissociates in water to form iron ions (Fe²⁺) and hydroxide ions (OH⁻). The balanced equation for this dissociation is Fe(OH)2 (s) ⇌ Fe²⁺ (aq) + 2 OH⁻ (aq). Understanding this dissociation is crucial for calculating the concentrations of the ions in solution, which are needed to apply the Ksp expression.

Calculating Solubility from Ksp

To calculate the solubility of iron(II) hydroxide from its Ksp value, one must set up the Ksp expression based on the dissociation reaction. For Fe(OH)2, Ksp = [Fe²⁺][OH⁻]². By substituting the solubility (s) into this expression, where [Fe²⁺] = s and [OH⁻] = 2s, one can solve for s, which represents the solubility in moles per liter. This value can then be converted to grams per 100 mL of solution.