What is the primary effect of impurities on the saturation point of a solution?

The primary effect of impurities on the saturation point of a solution is that they decrease the saturation point. When a solute is added to a solvent, the presence of impurities can disrupt the solute-solvent interactions. This results in a reduced capacity of the solvent to dissolve more of the solute because the impurities can interfere with the formation of a saturated solution.

In a pure solvent, a specific amount of solute can dissolve at a given temperature to reach saturation. However, when impurities are present, they often act as additional solute particles that do not contribute to the dissolution of the original solute. This can lead to a situation where the solution can hold less of the original solute before saturation is reached, effectively lowering the saturation point.

This phenomenon can be understood through concepts like colligative properties, where the presence of non-volatile solutes affects the physical properties of the solvent, including its boiling point and freezing point, and consequently its ability to achieve saturation with other solutes.