How much ethylene glycol (C2H6O2, the major component of antifreeze) must be added to 1 L of water to keep it from freezing at -20 oC?

Question

Kf = 1.86 oC/m.

Answer 1

delta T = Kf*m
You know delta T (it's 20C), and Kf, solve for m.

Then m = mols/kg solvent.
You know m and kg solvent (1 kg), solve for mols.

Then mols = grams/molar mass
You know mols and molar rmass, solve for grams.