Textbook Question
(a) True or false: 'solubility' and 'solubility-product constant' are the same number for a given compound.
Ch.17 - Additional Aspects of Aqueous Equilibria
Chapter 17, Problem 53b
(b) It is found that 1.1 × 10-2 g SrF2 dissolves per 100 mL of aqueous solution at 25°C. Calculate the solubility product for SrF2.
Verified step by step guidance1
Determine the molar mass of SrF2 by adding the atomic masses of Sr and F. Use the periodic table to find these values.
Convert the mass of SrF2 dissolved (1.1 × 10^-2 g) into moles using the formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \).
Calculate the molarity of the SrF2 solution by dividing the moles of SrF2 by the volume of the solution in liters (0.1 L).
Write the dissociation equation for SrF2: \( \text{SrF}_2 (s) \rightleftharpoons \text{Sr}^{2+} (aq) + 2\text{F}^- (aq) \).
Use the stoichiometry of the dissociation equation to express the concentrations of \( \text{Sr}^{2+} \) and \( \text{F}^- \) ions in terms of the molarity of SrF2, and then calculate the solubility product \( K_{sp} = [\text{Sr}^{2+}][\text{F}^-]^2 \).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Solubility Product Constant (Ksp)
The solubility product constant (Ksp) is an equilibrium constant that applies to the solubility of sparingly soluble ionic compounds. It is defined as the product of the molar concentrations of the ions, each raised to the power of their coefficients in the balanced equation. For SrF2, Ksp can be expressed as Ksp = [Sr^2+][F^-]^2, where [Sr^2+] and [F^-] are the molar concentrations of strontium and fluoride ions, respectively.
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Dissociation of Ionic Compounds
Ionic compounds like SrF2 dissociate into their constituent ions when dissolved in water. For SrF2, the dissociation can be represented as SrF2 (s) ⇌ Sr^2+ (aq) + 2F^- (aq). Understanding this dissociation is crucial for calculating the concentrations of the ions in solution, which are necessary for determining the Ksp.
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Calculating Molarity
Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. To calculate the molarity of SrF2 in the given problem, one must first convert the mass of SrF2 dissolved into moles using its molar mass, and then divide by the volume of the solution in liters. This step is essential for finding the concentrations of Sr^2+ and F^- ions needed to compute the Ksp.
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Related Practice
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