Homework Help: Freezing Point Depression and Ethylene glycol

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1. Oct 18, 2007

sam.

1. The problem statement, all variables and given/known data

Ethylene glycol, the primary ingredient in antifreeze, has the chemical formula C_2H_6O_2. The radiator fluid used in most cars is a half-and-half mixture of water and antifreeze.

What is the freezing point of radiator fluid that is 50% antifreeze by mass? K_f for water is 1.86 degrees Celsius/m.

2. Relevant equations

$$\Delta$$T_f = K_f * m

m (molality) = # of moles of solute/mass of solution (kg)

3. The attempt at a solution

Okay, so I assumed 100 g of solution. And the molar mass of ethylene glycol is 62.08 g/mol. So you find the moles of ethylene glycol by multiplying 50 g by the molar mass which gives you 0.805 mol. Then you assume 100 g of water (which is 0.1 kg). And you solve for molality (m) and then you just sub it into the first equation? Is this correct?

2. Oct 19, 2007

chemisttree

Not quite. Remember this:

do not "...assume 100 g of water (which is 0.1 kg)."

3. Apr 7, 2010

Palestinian

m (molality) = moles of solute/ mass of SOLVENT (KG) "NOTTTTTTTTTT SOLUTION"

4. Apr 8, 2010

Staff: Mentor

You not only necroposted in the thread that is over two years old, but you also missed the fact that chemisttree already addressed the problem.

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5. Apr 13, 2010

chemisttree

Boy! Those were the good old days. eh?