We can calculate the amount of freezing point depression that will occur using the following equation:

Question

ΔT = ikfm

where ΔT is the amount of the change in the freezing point, i is the number of particles dissolved, kf is a constant (different for each solvent), and m is the concentration of dissolved material. This concentration has units of mol per kg solvent.

With this in mind, lets calculate the amount of depression that will occur when 5 g of sodium chloride is dissolved into 0.250 kg of water. Remember when sodium chloride dissolves in water it breaks into two particles. The kf for water is 1.86 0C/m.

Report you answer with two decimal points and no units.

Answer 1

ΔT = i*Kf*m
ΔT = ?
i for NaCl is 2.
Kf = 1.86
m = moles/kg = (5 g/58.5)/0.250
Plug and chug.

Answer 2

Question, How did you get 2. for I? Was the number based on the melting or boiling points of the salt or something else completely?