The phrase “like dissolves like” refers to the fact that polar solvents dissolve nonpolar solutes and vice versa condensed phases can only dissolve other condensed phases gases can only dissolve other gases polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes solvents can only dissolve solutes of similar molar mass.
The Correct Answer and Explanation is:
The correct answer is:
“Polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes.”
Explanation:
The phrase “like dissolves like” is a fundamental principle in chemistry used to predict solubility—the ability of one substance (the solute) to dissolve in another (the solvent). This phrase means that substances with similar chemical characteristics, particularly polarity, tend to dissolve in each other.
Polarity refers to the distribution of electric charge around molecules. Polar molecules have uneven charge distributions resulting in partial positive and negative ends (dipoles), whereas nonpolar molecules have a more even distribution of charge, meaning no significant dipoles.
- Polar solvents (like water, ethanol) have molecules with significant dipoles. They dissolve polar solutes (like salts, sugars, or other polar molecules) because of strong intermolecular forces such as hydrogen bonding, dipole-dipole interactions, and ion-dipole interactions. These interactions help separate and surround solute molecules, effectively dissolving them.
- Nonpolar solvents (like hexane, benzene) have molecules without significant dipoles. They dissolve nonpolar solutes (like oils, fats, or hydrocarbons) through London dispersion forces (van der Waals forces). Since nonpolar molecules do not have charges to interact strongly with polar molecules, nonpolar solvents cannot dissolve polar substances well.
Why the other options are incorrect:
- “Polar solvents dissolve nonpolar solutes and vice versa” is incorrect because polar solvents generally cannot dissolve nonpolar solutes effectively due to lack of compatible intermolecular interactions.
- “Condensed phases can only dissolve other condensed phases” is false because gases can dissolve in liquids (like oxygen in water), and liquids can dissolve solids, gases, or other liquids.
- “Gases can only dissolve other gases” is incorrect because gases can dissolve in liquids and solids, for example, carbon dioxide in soda.
- “Solvents can only dissolve solutes of similar molar mass” is also incorrect. Molar mass affects properties like boiling point and vapor pressure but does not govern solubility directly. Polarity and molecular interactions are much more significant.
In summary, the phrase “like dissolves like” emphasizes the importance of polarity in solubility, explaining why polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes effectively. This principle is essential for understanding mixtures, chemical reactions, and many natural and industrial processes.
