Quelle masse de fluorure de magnésium MgF2 peut-on dissoudre, a) dans 200 mL d'eau pure? b) dan

step 1 So first we need to determine the concentration of MG2 plus cations and then the value of QSP in

Quelle masse de fluorure de magnésium MgF2 peut-on...

Quelle masse de fluorure de magnésium $\mathrm{MgF}_2$ peut-on dissoudre,
a) dans $200 \mathrm{~mL}$ d'eau pure?
b) dans $200 \mathrm{~mL}$ d'eau contenant déjà $5,0 \mathrm{~g}$ de chlorure de magnésium $\mathrm{MgCl}_2 ?$

Key Concepts

Solubility Equilibrium

This concept refers to the dynamic balance established between a sparingly soluble solid and its ions in solution. In the context of a dissolving salt like MgF?, it describes how the rate of dissolution is equal to the rate of precipitation, leading to constant ion concentrations at equilibrium.

Solubility Product (Ksp)

The solubility product constant is the equilibrium constant specific to the dissolution of a sparingly soluble salt. It is defined as the product of the molar concentrations of the resulting ions each raised to the power of their stoichiometric coefficients. For salts like MgF?, the Ksp value provides a quantitative measure of the maximum solubility under given conditions.

Common Ion Effect

The common ion effect occurs when the solubility of a sparingly soluble salt is reduced by the presence of an ion already present in the solution. When another source of one of the ions from the dissolving salt is added, it shifts the equilibrium, decreasing the salt's solubility. This concept is crucial for understanding solubility changes in solutions that already contain common ions.

Dissolution Stoichiometry

Dissolution stoichiometry involves interpreting the balanced chemical equation governing the dissolving process. For MgF?, the equation illustrates that one mole of salt produces one mole of Mg²? ions and two moles of F? ions. This ratio is essential for relating the solubility of the salt to the concentration of its constituent ions in solution.

Molarity and Unit Conversions

This key concept covers the conversion between mass, moles, and concentration (molarity) in solution. It includes calculating the number of moles from given masses using molar masses, determining the molar concentration from the number of moles and volume of solvent, and finally, converting back to grams if needed. These calculations underpin the quantitative aspects of solubility and equilibrium studies.

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