**Correct Option: C. The polarity of the solute and solvent** ### Detailed Explanation: 1. **Understanding Solubility**: - Solubility is the ability of a solute (the substance being dissolved) to dissolve in a solvent (the substance doing the dissolving) at a given temperature and pressure. The solubility of a solid in a liquid is influenced by various factors, but the most significant is the interaction between the solute and solvent molecules. 2. **Polarity**: - Polarity refers to the distribution of electrical charge over the atoms joined by the bond. Molecules can be polar (having a positive and a negative end) or nonpolar (having an even distribution of charge). - "Like dissolves like" is a common rule in chemistry. This means that polar solutes tend to dissolve well in polar solvents, while nonpolar solutes dissolve well in nonpolar solvents. 3. **Why Option C is Correct**: - The polarity of both the solute and the solvent determines how well they interact. For example, when a polar solute (like sodium chloride, NaCl) is placed in a polar solvent (like water), the positive end of water molecules attracts the negative chloride ions, and the negative end attracts the positive sodium ions. This interaction leads to the solute dissolving effectively. - Conversely, if a nonpolar solute (like oil) is placed in a polar solvent (like water), the solute does not dissolve well because there are no favorable interactions between the molecules. 4. **Why Other Options are Incorrect**: - **A. The color of the solute**: - The color of a solute does not affect its solubility. Color is a physical property related to the absorption and reflection of light, not to the chemical interactions that determine solubility. - **B. The size of the solute particles**: - While the size of solute particles can influence the rate of dissolution (smaller particles dissolve faster due to a larger surface area), it does not fundamentally determine solubility. For example, both large and small particles of a polar solute can dissolve in a polar solvent if the polarity is compatible. - **D. The presence of other solutes in the solution**: - The presence of other solutes can affect solubility through phenomena like the common ion effect or changes in solvent properties, but it is not the primary factor. The fundamental interaction between the solute and solvent remains the most critical aspect of solubility. ### Summary of Key Points: - **Polarity is Key**: The interaction between polar and nonpolar molecules determines solubility. - **"Like Dissolves Like"**: Polar solutes dissolve in polar solvents; nonpolar solutes dissolve in nonpolar solvents. - **Color and Size are Irrelevant**: The color of a solute does not affect solubility, and while size can influence the rate of dissolution, it does not determine solubility. - **Other Solutes Matter, but Less**: The presence of other solutes can influence solubility, but the polarity of the solute and solvent is the most significant factor. This understanding of solubility is crucial for predicting how substances will behave in solutions, which is a fundamental concept in chemistry.