Molar solubility

Definition

Molar solubility is the number of moles of a solute that can dissolve in one liter of solution at a given temperature, expressed in units of moles per liter (mol/L). This concept is crucial for understanding how solutes dissolve in solvents and is directly related to the solubility product constant (Ksp), which quantifies the equilibrium between solid and dissolved species in a saturated solution.

5 Must Know Facts For Your Next Test

1. Molar solubility is dependent on temperature; as temperature increases, molar solubility typically increases for most salts.
2. The molar solubility can be calculated from Ksp values by establishing a relationship between the concentrations of dissolved ions and the Ksp expression.
3. Different ionic compounds have different molar solubilities; for example, barium sulfate has low molar solubility, while sodium chloride has high molar solubility.
4. In a saturated solution, any additional solute will not dissolve but will remain as a solid, maintaining equilibrium between dissolved ions and undissolved solute.
5. The presence of common ions can significantly affect the molar solubility by shifting the equilibrium position according to Le Chatelier's principle.

Review Questions

• How does molar solubility relate to the concept of Ksp?
  • Molar solubility is closely linked to Ksp, as Ksp is used to determine the molar solubility of ionic compounds. The Ksp expression includes the concentrations of ions that are produced when a salt dissolves. By setting up an equation using Ksp and substituting in values for molar solubility, one can calculate how much of a particular compound can dissolve in solution before reaching saturation.
• Discuss how temperature changes affect molar solubility and provide examples.
  • Temperature has a significant impact on molar solubility; typically, as temperature increases, so does the solubility of most solids. For instance, sodium nitrate's molar solubility rises sharply with temperature, while some salts like calcium sulfate show decreased solubility with increasing temperature. Understanding this relationship is vital for predicting how different conditions can affect dissolving processes in various solutions.
• Evaluate the role of the common ion effect on molar solubility and its implications in real-world applications.
  • The common ion effect reduces the molar solubility of salts when another source of one of its ions is introduced into the solution. This principle is widely applied in environmental chemistry, such as controlling the solubility of heavy metals in wastewater treatment processes. By manipulating ion concentrations through strategies like adding salts that share common ions, it becomes possible to reduce contaminant levels effectively and achieve desired environmental outcomes.

Related terms

Solubility product constant (Ksp): The equilibrium constant for a solid dissolving in an aqueous solution, representing the product of the molar concentrations of the ions each raised to the power of their coefficients in the balanced equation.

Saturated solution: A solution in which the maximum amount of solute has been dissolved at a given temperature, resulting in equilibrium between the dissolved ions and undissolved solute.

Common ion effect: The phenomenon where the solubility of a salt decreases in a solution that already contains one of its constituent ions, due to Le Chatelier's principle.