**Correct Option: C. Stirring the solution to enhance mixing** ### Detailed Explanation: To understand why stirring the solution is the most effective way to increase the solubility of a solid solute in a liquid solvent, we need to consider the factors that influence solubility. 1. **Solubility Basics**: - Solubility is the ability of a solute (in this case, a solid) to dissolve in a solvent (a liquid). The solubility of solids in liquids generally increases with temperature, but this is not the only factor at play. 2. **Option A: Decreasing the temperature of the solvent**: - **Why it's incorrect**: For most solid solutes, solubility increases with temperature. Lowering the temperature typically decreases the kinetic energy of the molecules, which reduces the solubility of the solid in the liquid. There are exceptions (like some salts), but generally, this option does not promote solubility. 3. **Option B: Increasing the pressure of the system**: - **Why it's incorrect**: Pressure has a significant effect on the solubility of gases, not solids. For solids dissolving in liquids, pressure changes have minimal impact because solids and liquids are relatively incompressible. Therefore, increasing pressure does not enhance the solubility of a solid solute. 4. **Option C: Stirring the solution to enhance mixing**: - **Why it's correct**: Stirring increases the interaction between the solute and solvent molecules. When you stir a solution, you help distribute the solute particles throughout the solvent more evenly. This increases the rate at which the solute dissolves because it allows more solute particles to come into contact with the solvent, facilitating the breaking of intermolecular forces that hold the solid together. This is particularly important for solids, as they often have a slower dissolution rate compared to liquids. 5. **Option D: Using a solvent that has a lower polarity than the solute**: - **Why it's incorrect**: The principle of "like dissolves like" applies here. Polar solutes tend to dissolve well in polar solvents, while non-polar solutes dissolve better in non-polar solvents. If the solvent has a lower polarity than the solute, it is less likely to effectively solvate the solute particles, leading to lower solubility. ### Summary of Key Points: - **Stirring enhances solubility** by increasing the contact between solute and solvent, promoting faster dissolution. - **Temperature generally increases solubility** for solids, so decreasing temperature is counterproductive. - **Pressure affects gas solubility** more than solid solubility, making it an ineffective factor for solids. - **Polarity matters**: Using a solvent with lower polarity than the solute is unlikely to increase solubility. ### Revision Summary: - Stirring a solution increases solubility by enhancing mixing. - Decreasing temperature usually decreases solid solubility. - Pressure has minimal effect on solid solubility in liquids. - Solvent polarity should match solute polarity for effective dissolution.