Chapter 14.3

# Chapter 14.3 - Molecular weight: Example illustrating the...

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11 MSE 2090: Introduction to Materials Science Chapter 14, Polymer Structures Molecular weight: Example illustrating the difference between number-average and weight-average student weight mass (lb) 1 104 2 116 3 140 4 143 5 180 6 182 7 191 8 220 9 225 10 380 What is the average weight of students in this class: a) Based on the number fraction of students in each mass range? b) Based on the weight fraction of students in each mass range? Solution: The first step is to sort the students into weight ranges (let’s use 40 lb ranges). weight range # of students mean weight number fraction weight fraction N i M i x i w i 81-120 2 110 0.2 0.117 121-160 2 142 0.2 0.150 161-200 3 184 0.3 0.294 201-240 2 223 0.2 0.237 241-280 0 - 0 0.000 281-320 0 - 0 0.000 321-360 0 - 0 0.000 361-400 1 380 0.1 0.202 1881 = i i M N 10 = i N = i i i N N x = i i i i i M N M N w

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12 MSE 2090: Introduction to Materials Science Chapter 14, Polymer Structures Molecular weight: Example illustrating the difference between number-average and weight-average weight range # of students mean weight number fraction weight fraction N i M i x i w i 81-120 2 110 0.2 0.117 121-160 2 142 0.2 0.150
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## This note was uploaded on 02/14/2012 for the course MSE 2090 taught by Professor Leoindzhiglei during the Fall '10 term at UVA.

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Chapter 14.3 - Molecular weight: Example illustrating the...

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