Re: Boiling point elevation and freezing point dep

This answer can get fairly complicated.  For a thorough explanation, I
suggest looking it up in a physical chemistry textbook.  The one by Ira
N. Levine is a good source.

But in short, you need to know the "molal freezing point depression 
constant" and the "molal boiling point elevation constant."  This 
is the amount by which the boiling (or freezing) point changes for
every mole of solute that is added to a kilogram of the solution.
Be aware that solutes that ionize count as one mole per each ion
that is formed on dissociation.  So NaCl counts as "two moles", while
sucrose, which doesn't ionize, counts as only one.

For water, the boiling point elevation constant is 0.513 degrees Kelvin
for each mole of solute (or solute-ions) that is added to a kilogram of
solution.  The freezing point depression is 1.86 degress Kelvin.

If you go to a solvent other than water, the values are different.  LeVine
notes that the freezing point depression constant for benzene is 5.1,
for acetic acid is 3.8, and for camphor it is 40.