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##### Chemistry Solubility

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A solution is made with 52.0g of an unknown molecular solid with 500.0g of water.  Determine the molecular mass of the unkown molecular solid if the frezzingpoint of the solutions is -4.77c

Mar 26th, 2015

Ok first you must look up the constant for the freezing point depression of water.  That constant is 1.86 degrees C /m.   You were given 500 g water to do these problems you must change grams into kilograms.  500g x 1Kg/1000g = .5 kg H20

Next we use the formula for freezing point depression ...   delta(change) T = i  Kf m

m stands for mol

i is 1 for water

So I will write it as a formula        4.77 = i (1.86 c/mol) (.5kg H2O)      Then multiply 1.86 x .5  = .93

thus..   4.77C = .93 M  lets find how many mols of unknown we have by dividing 4.77/.93 = m     you will get 5.13mol

Your Unknown was 52g / 5.13mol   =   10.1 g/mol       So the answer is 10.1

Mar 28th, 2015

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Mar 26th, 2015
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Mar 26th, 2015
Dec 3rd, 2016
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