[Iodina]

I'm trying to figure out what mass ratio of Water:Propylene Glycol will give a freeze point of -6.

The formula is delta T=Km
deltaT= 6
K=1.86
then I calculate m=3.226 mols Prop.Glyc./Kg water
I then multiply by 76.09 g/mol Prop.Glyc. and divide by 1000 to switch g and Kg
the answer I get is 4.07 g water: 1 g Prop. Glyc.
but I believe it should be 4.70. Where is my mistake?

[macman104]

I didn't check the math, but is there a reason you *believe* it should be 4.70?