How could the freezing point depression of #CaCl_2# be smaller than #NaCl#?
It depends on whether you are calculating on a molar or mass basis. Calcium chloride gives more freezing point depression per mole than sodium chloride, but less freezing point depression per gram.
Let's see how the mass basis is different. Say you have two solutions, one of them with 50 grams
Now let's do this with the
The calcium chloride solution, with the same number of grams per liter, makes fewer ions in solution (
However, you can get a lot more mass concentration into solution with