HW1 Solutions

# HW1 Solutions - ChE178:ProblemSet#1...

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Ch E 178: Problem Set #1 Due Friday, September 5, 2008 1. A polymer is synthesized by the step growth polymerization. Analysis of the product showed that it is composed of a series of fractions of molecules of different molecular weights: Fraction No. wt. fraction, Wi/W Mi, molecular wt. 1 0.1 24,000 2 0.14 42,000 3 0.15 70,000 4 0.18 98,000 5 0.14 146,000 6 0.12 204,000 7 0.1 244,000 8 0.07 292,000 a) Which molecular weight fraction contains the largest number of polystyrene molecules? We’ll denote the number of molecules by Ni.  Then,  Mi Wi Ni = .  We can compare  W Ni (where W is the total weight of all the fractions), which is then the wt. fraction divided by  Mi.  Add a column to the given table for  Mi fraction wt W Mi Wi W Ni . = = .  From the column, you  can see that  Fraction No. 1  has the largest number of polymer molecules.   Fraction No. wt. fraction, Wi/W Mi, molecular wt. # molecules / total weight (Ni/W)

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HW1 Solutions - ChE178:ProblemSet#1...

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