solvent
Summary
The solvent is the component of a solution that dissolves the others (the solutes), usually the one present in the largest amount. By "like dissolves like," polar solvents such as water dissolve ionic and polar solutes, and nonpolar solvents dissolve nonpolar ones.
Detail
Meaning: The solvent is the component of a solution that dissolves the others (the solutes). It is usually the component present in the greatest amount, and the solution takes its phase. Dissolving is favorable when solute–solvent attractions make up for the solute–solute and solvent–solvent attractions that are broken. Like dissolves like: polar solvents such as water dissolve ionic and polar solutes through ion–dipole interactions and hydrogen bonding; nonpolar solvents such as hexane dissolve nonpolar solutes through London dispersion forces.
Equation: ΔTf = i Kf m, where ΔTf is the freezing point depression (K), i is the van't Hoff factor (unitless), Kf is a constant that belongs to the solvent (K·kg/mol), and m is molality, moles of solute per kilogram of solvent (mol/kg).
On the MCAT: Expect questions that predict solubility from polarity, or that use colligative properties: more dissolved particles lower the solvent's vapor pressure and freezing point and raise its boiling point and osmotic pressure.
Common confusion: Molality uses the mass of the solvent, while molarity uses the volume of the whole solution. Also, a solvent need not be a liquid, though liquids are the usual MCAT case.
Sources
- Chemistry: The Central Science
- General Chemistry: Principles and Modern Applications
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.