posted by E. Lee
What is a minimum volume (in gallons) of ethylene glycol (CH2OHCH2OH, an antifreeze) that has to be added to 3.00 gal of water if you desire this engine cooling solution (for a auto radiator) NOT to be frozen below - 34.1 oC - a very cold Siberian or Canadian winter temperature?
What is molar mass of ethylene glycol?
The required molality of ethylene glycol:
The required volume of ethylene glycol in gallons:
Convert 3.00 gallons H2O to grams.
delta T = Kf*m
34.1 = 1.86*m
Sole for m.
m = mols glycol/kg solvent
You have m and kg solvent (from the 3.00 gallons H2O), solve for mols ethylene glycol.
mols glycol = grams glycol/molar mass glycol. You know mols and molar mass, solve for grams ethylene glycol and convert that to gallons. You will need the density of ethylene glycol which isn't given in the problem. Post your work if you get stuck.
density of water and the antifreezer is 0.9975 g/mL and 1.141 g/mL
I got molality of 54.5 and molar mass 18.33g.
The molar mass of ethylene glycol is 62.068 (just add atomic masses for CH2OHCH2OH).
molality = 18.33; I think you just made a typo for that in your post.
34.1 = Kf*m
34.1/1.86 = 18.333m
I don't know what the 54.5 represents.
I converted 3 gallons to grams and obtained 11,327.97 using 0.9975 g/cc for density and 453.6 g/lb.