Depression of the Freezing Point of a Solvent
We need two pieces of information to calculate the depression of the freezing point of the solvent in a solution containing a nonvolatile nonelectrolyte:
• The molal concentration, m, of the solute in the solution (Sometimes it may be necessary to calculate this concentration from other information.)
• The freezing point depression constant, Kf, for the solvent.
We use the following equation to calculate a freezing point depression. (Note: This equation assumes the freezing point depression constant has a positive value.)