Question

What is the freezing point of radiator fluid that is 50% antifreeze by mass? kf for water is 1.86 ∘c/m?

Answer 1

Ethylene glycol, the primary ingredient in antifreeze, has the chemical formula C2H6O2 . The radiator fluid used in most cars is a half-and-half mixture of water and antifreeze.

Take 1000 g of solution; then you would have 500 g ethylene glycol and 500 g water.

Mol. mass C2H6O2 = 2(12) + 6(1) + 2(16) =62 g/mole

Molality = total C2H6O2 in solution / (mol. mass)(kg water)

Molality = 500g / (62 g/mole)(0.500 kg) =16.1 m

delta T = Kbp X m = (0.512 C / m)(16.1 m) = 8.24 C

So the boiling point = 100 C + 8.24 C = 108.24 C

F = 9/5C - 32 = 9/5(108.24) -32 = 226.8 F