Fall2011_Exam 3&4 Soln

Fall2011_Exam 3&4 Soln - ChE 350 Fall 2011 (of 200...

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Unformatted text preview: ChE 350 Fall 2011 (of 200 points) Exam 3 and SHOW YOUR WORK!!! I. (70 pts) Molecular weight data for a sample of polystyrene are tabulated below. ~ ~ (i]) fjiI!' ./(a) Write the chemical formula for the repeat unit of polystyrene:- ~ - ~ - U@ (2 S )/f1if~) Fill in the blanks in the table, calculating mole fraction, weight fraction, XI M and w, M,. (,) ~~) Compute the number average molecular weight: 'L::t, ODD r/l-l.o I (<) f;:fi!f~) Compute the weight average molecular weight: 7- b', Y cr I ?/J'ltP I (I t t! . ., ~ ") rO C-J~~kclCoter5 (e) Determine the average degree of polymerization: ~ ~ A 0 - (I 0) v{f) Compute the polydispersity index: _-Z=-.=--8 '=---=-?~2,-- _ (10) V (g ) Would this polymer be considered monodisperse? No Po 1:'/ '/1 ) Number of Mass of each Mole Weight Molecules Molecule (Mi, Fraction (Xi) Fraction (w.) xjMj w. M, z/mol) 500 5000 0.311 o.() c 2 Ji~67- 10r 400 12000 0, 7. 6 =t 0.11 ? 1700 I J 4 Z Z o. J :r~ , l.{, zt? 300 24000 O,20 4, g--o 200 55000 0.153' o. 27-7 ?1?J 1'I,CfJf' 100 150000 o.oe+ (J,17Q (O, 000 <;)}) t o e~ e ru./ fo rl"'H 'f. I'd: 1/' . tv. :P;/1,- fa) Xi :: '* NT-=- ~~ . :;: )00..,. '10(}+,..-liot>:= 1,00 1 L M-r I {) Fin = Xi 1 '1, ={O:nl)('i()IJO)"'.~ M r = t. (/.Ii11J~((ODJ(~bOO )+... .,( loo)(lrq J , 11 =2 ~ 0 0 0 :/}'kl/ t'T J-o. I M ...- z: ~.ot; )(/0 J)) n:::~ w- f1~ = : (dO/:'2){fQOt;)t . 1 (0,~ 1- VI l _' fi:,:: '7 6 , 'If{ I '1 / ~ ( ) ~;'Z#~r3 f) i+I" (~)}.g) 1- (-)( I) = /0'1 0/;"0 J . 2-=lO ()O 60 f)OP ~~ :: ~= 2-t'- I 'i I F) tOl ~~~.1i:f!f-= 2J(?3 l'f.t z ~ Q()O I ehE 350 Fan 2011 (of 200 points) Exam 3 and SHOW YOUR WORK!!!...
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Fall2011_Exam 3&4 Soln - ChE 350 Fall 2011 (of 200...

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