Can anyone help with this?

Question

Calculate the freezing point of watercaused by dissolving 3.8m of CaCl2 (Kf=1.0 Degrees C/m). Would this be sufficient to prevent ice from forming on the sidewalk?

Answer 1

For electrolytes

ΔT=i*Kf*m

where i is the van't Hoff coefficient. For strong electrolytes (like CaCl2) it is equal to the number of ions that are produced by their dissociation according to their molecular formula.
CaCl2 -> Ca+2 +2Cl- So there are 3 ions (1 Ca+2 and 2 Cl-) so i=3

ΔT= 3*1.0*3.8 = 11.4
So the freezing point of water becomes Tf=Tf0-ΔT =0-11.4= -11.4 C

So if the temperature is above -11.4 C there will be no ice forming.

Note: If I remember correctly for water Kf=1.86 but anyway I did the math with the values you gave us.