pure solvent as a solid. This will be a lower temperature in solution and explains why salt is added to roads to melt the ice. The maximum freezing point is 0 degrees Fahrenheit, which is -18 degrees Celsius under high concentrations of sodium chloride. As you can imagine, Calcium chloride will be used for lower temperatures because it divides into three ions, rather than two because its chemical formula is CaCl2 (breaking into one ion of calcium and 2 ions of chloride). Osmosis is the diffusion of a fluid through a semipermeable membrane. Only the solvent is able to pass through the membrane and not the solute. The osmotic pressure of a solution is dependent upon the molar concentration of the particles in solution and is the pressure difference needed to stop the flow of a solvent across a semipermeable membrane. It is calculated based on the ideal gas constant (0.0821 Liters atmospheres per mole per degree kelvin), which is designated as R. This makes the osmotic pressure equal to MRT, where M is the molar mass of the solute, R is the gas constant, and T is the temperature in kelvin. Vapor pressure involves the ability of the liquid to switch to the gas phase at the top of the liquid surface. Regardless of the solvent, when it comes to a solution, the vapor pressure will be lowered. This is also going to be independent of the solute. As a colligative property, it depends on how many solute particles will be dissolved in the solution. It will be directly proportional to the concentration of the solute. Because it uses Raoult’s law, it is proportional to the mole fraction of the solute rather than on molality or molarity. Vapor pressure of the solution will be the mole fraction of the solvent multiplied by the vapor pressure of the solvent alone. The mole fractions of solvent and solute will add up to 1.
ANOMALOUS COLLIGATIVE PROPERTIES Anomalous colligative properties are colligative properties that deviate from the norm. Colligative properties are those properties of solutions that rely on the concentration of solute particles in an ideal solution, such as vapor pressure lowering, boiling point elevation, osmotic pressure, and freezing point depression. In these properties, there is a direct relationship between the concentration and the property seen. Some solutes
151
