Calculate the molar solubility of SrF2 in: (a) 0.010 M Sr(NO3)2 (b) 0.010 M NaF.

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Step 1: Write the dissolution equation for SrF2: SrF2(s) ⇌ Sr²⁺(aq) + 2F⁻(aq).

Step 2: Write the expression for the solubility product constant (Ksp) of SrF2: Ksp = [Sr²⁺][F⁻]².

Step 3: For part (a), consider the common ion effect from Sr(NO3)2. The concentration of Sr²⁺ from Sr(NO3)2 is 0.010 M. Let the molar solubility of SrF2 be 's'. The total [Sr²⁺] = 0.010 + s and [F⁻] = 2s.

Step 4: Substitute the concentrations into the Ksp expression for part (a): Ksp = (0.010 + s)(2s)². Since s is small compared to 0.010, approximate [Sr²⁺] ≈ 0.010.

Step 5: For part (b), consider the common ion effect from NaF. The concentration of F⁻ from NaF is 0.010 M. Let the molar solubility of SrF2 be 's'. The total [F⁻] = 0.010 + 2s and [Sr²⁺] = s. Substitute these into the Ksp expression: Ksp = s(0.010 + 2s)². Since s is small compared to 0.010, approximate [F⁻] ≈ 0.010.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

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 (M). It is a crucial concept in understanding how solutes interact with solvents and is often used to describe the solubility of ionic compounds in solution.

Common Ion Effect

The common ion effect describes the decrease in solubility of an ionic compound when a common ion is added to the solution. This phenomenon occurs because the addition of a common ion shifts the equilibrium position of the dissolution reaction, leading to reduced solubility. In the case of SrF2, the presence of Sr^2+ or F^- ions from other sources will affect its solubility.

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 the ions at equilibrium. For SrF2, the Ksp expression involves the concentrations of Sr^2+ and F^- ions, which are essential for calculating molar solubility in different ionic environments.

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