Solutions and Colloids

Properties of your substance will differ depending on whether your substance is a pure solute or solvent. Having impurities will change the properties of the substance you are studying.

Colligative Properties (2:48)

Colligative Properties Vocabulary

vapor pressure lowering: once you dissolve a nonvolatile substance in volatile liquid, the vapor pressure will lower

boiling point elevation: once you dissolve a substance into a solvent, the boiling point of the solvent increases.

freezing point depression: once you dissolve a substance into a solvent, the freezing point of the solvent decreases.

osmotic pressure (Π): once you dissolve a substance into a solvent on one side of a semi-permeable membrane, there is a pressure associated with the movement of solvent from one side of the membrane to the other in order to balance the concentrations.

van’t Hoff factor (i): ratio of moles of particles in solution to moles of formula units that are dissolved; # of electrolytes

Important Equations

Pj is the vapor pressure of substance j in the solution, xj is the mole fraction of substance j in the solution, and Pj° is the vapor pressure of pure substance j.

∆Tb is the change in boiling point of the solvent, Kb is the boiling point elevation constant for the solvent, m is the molality of the solute, and i is van't Hoff factor.

∆Tf is the change in freezing point of the solvent, Kf is the freezing point depression constant for the solvent, m is the molality of the solute, and i is van't Hoff factor.

Π is the osmotic pressure, i is the van't Hoff factor, M is the molarity of the solute, R is the gas constant, and T is the temperature.