GEN CHEM 1 | Colligative Properties of Solutions

Colligative Properties

depend only on the concentration of the solute, and not the nature of the solute’s particles

Non-electrolyte Compounds

do not ionize/dissociate into ions in solutions and do not conduct electricity

Non-volatile Substances

do not vaporize rapidly

Vapor Pressure Lowering

For a non-electrolyte solution containing a nonvolatile solute, the vapor pressure of its solution is always lower than that of the pure solvent.

Raoult’s Law

[Vapor Pressure of the Solution (P₁)] = [mole fraction of the solvent (X₁)][Vapor pressure of pure solvent (P₁º)]; expressed in mm Hg

Boiling Point Elevation | Definition

a solution’s boiling point is always greater than that of a pure solvent

Boiling Point Elevation | Formula (Subtraction)

[Boiling Point Elevation (^T_b)] = [Boiling Point of Solution (T_b)] - [Boiling Point of Pure Solvent (T_bº)]

Boiling Point Elevation | Formula (Multiplication)

[Boiling Point Elevation (^T_b)] = [Molal Boiling Point Constant (K_b | ºC/m)] * [molality of solution (m)]

Freezing Point Depression

A solution’s freezing point is always less than the freezing point of the pure solvent.

Freezing Point Depression Formula (Subtraction)

[Freezing Point Depression (^T_f)] = [Freezing Point of Pure Solvent (T_fº)] - [Freezing Point of Solution (T_f)]

Freezing Point Depression Formula (Multiplication)

[Freezing Point Depression (^T_f)] = [Molal Boiling Point Constant (K_f | ºC/m)] * [molality of solution (m)]

Osmotic Pressure (π)

the pressure required ti stop osmosis; expressed in atm

Osmotic Pressure Formula

[Osmotic Pressure (π)]=[molarity of the solution (M)]*[gas constant (R; 0.0821 L atm/ mol K)]*[absolute temperature (T)]

Tonicity

based on the difference between the concentrations of two solutions

Isotonic

when solutions have equal concentrations; they have the same osmotic pressure

Hypertonic

more concentrated solution

Hypotonic

the more dilute or less concentrated solution