14pts
in the winter of 1994, record low temperatures were registered throughout the united states. for example, in champaign, illinois, a record low of -29°f was registered. at this temperature can salting icy roads with cacl2 be effective in melting the ice? (the solubility of cacl2 in cold water is 74.5 g per 100.0 g of water.)
(a) assume i = 3.00 for cacl2.
(b) assume i = 2.60

why does it work for 3.00 but not 2.60? i'm confused as to how i process this question and explain it.

Hi, thank you for posting your question here at .

Freezing point depression is one of the colligative properties. Its equation is



where the solvent is water. Thus, TF,solvent = 0 degrees Celsius and Kf is 1.86 kg/mol-C. i is the vant Hoff factor and TF,solution is -29 degrees = -33.9 degrees Celsius. Substituting,

For i = 3,

molality = 6.08 mol  CaCl2/kg water

For i=2.6

molality = 7 mol CaCl2/kg water

We compare the values of the molalities to the solubility. Molecular weight of CaCl2 = 111 g/mol.

Solubility = (74.5 g/100g)(1 mol /111g)(1000 g/1 kg)
Solubility = 6.71 mol CaCl2/kg water

Since at 7 mol CaCl2/kg water (when i=2.6) is greater than the solubility, then it will not be possible. 

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