The common ion effect impacts which of the following?

The common ion effect primarily influences molar solubility. This phenomenon occurs when the solubility of a salt is reduced in a solution that already contains one of the ions present in that salt. For example, if a salt such as calcium fluoride (CaF2) is added to a solution that already has fluoride ions (F-), the presence of these common ions shifts the equilibrium according to Le Chatelier's principle. This results in a decrease in the molar solubility of the salt because the equilibrium shifts to favor the solid form of the salt, thereby reducing the concentration of dissolved ions in the solution.

It's important to note that while the solubility product constant (Ksp) is a characteristic of a particular salt at a specific temperature and does not change due to the common ion effect, the molar solubility of that salt does decrease when a common ion is introduced. This is because the presence of additional ions affects the overall equilibrium of the dissolution reaction, leading to less dissolution of the salt.

Understanding the common ion effect is crucial in various applications, such as predicting how solubility will change in different environmental conditions or in analytical chemistry when separating ions in solution.