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Unformatted text preview: University of Toronto
Department of Materials Science and Engineering
Kinetics Module of RISE21711182
FINAL EXAMINATION Monday April 16'“ 2007, 14:00—16:30 WRITE USING CA PITAL LETTER #ﬁwﬁfj FIRST NAME:
LAST NAME: _
STUDENT NUMBER:
SIGNATURE: l ANSWER ALL THREE PROBLEMS page I of IO pages PROBLEM 1 (MARKS 15) The tollowing elementary reaction A —> B is carried out inn plug ﬂow reactor in which the volumetric flow rate, U , is constant. Derive an equation relating the reactor
volume to the entering and exiting concentrations of A, the rate constant k, and the volumetric flow rate 1). Determine the reactor volume necessary to reduce the exiting
concentration to 5% ofthe entering concentration when the volumetric ﬂow rate is 20 lit
min'l and the speciﬁc reaction rate ,k, is 0.45 min“. HINT: In a plug ﬂow reactor the molar ﬂow rate F obeys the following relationship: dFA
(1V V Volume ofplug ﬂow reactor :rA 1}; Rate of reaction with respect of Reactant A page 2 of IO pages pagc 3 of 10 pages PROBLEM 2 ( MARKS 15) A) During the experimentation ofthe reaction:
A (ﬂuid) + bB (solid) 6 Fluid and Solid Products
11 was found that it follows the shrinking core model. In addition results with different particle sizes have found that the "C is proportional to the particle radii.
Can you deduce the mechanism which controls the conversion of particles 2’ and if not
what additional tests can you suggest ? B) The same homogeneous reaction takes place in two ideal ﬂow reactors. In both
reactors the concentration of a reactant A was measured at different locations shown.
From the graphs shown below can you identify the type ofreaclor( mixed ﬂow or plug ﬂow) ? Justify your answer L'llll‘dllUll (Kinccuzt'a‘duu
(jun i ’ g A _
t.,.__.,___,..__ , . .. ._ .. , l’l~~i1it. Hawma: Reactor .\ Reactor ll page 4 of l“ pages C) The following reaction takes place in a batch reactor:
A ——) products At time t = 0 the concentration of A is [A] = 20 mol "1'3. In this reactor you have
inserted a sensitive probe which measures the concentration of A. You have found the
following data: Time (min) Concentratigg of A in nﬂm" What you can say about the order ofthis reaction ? (Justify your answer) page 5 of If! pages age 6 of IO pages x page 7
of
10 pages PROBLEM 3 ( MARKS 20) Spherical panieles of Zinc Sullide. [118, of size R=l mm are roasted in a gas
. . v . . . . . ‘
stream containing 8 molar % Oxygen at 900 ( and l atm. lhe storcluometry ol the reaction is:
2 7.118 + 3 01 —> 2 ZnO + 2 SO;
A) Calculate the time needed for 75% conversion ofa particle assuming: I The gas stream dilTusion through the ZnO controls and
2. The surface reaction controls B) Estimate the relative resistance of 7.110 product layer assuming complete
conversion ofthe particle. Assumptions l) The above reaction proceeds by the shrinking core model, 2) The gas
lilm resistance can be neglected since the 7.110 growing product layer is present, 3) The
gas stream follows the ideal gas law. DEFINITIONS 1) Ttotal = Tnin‘usion + TChemical Reaction 2) Relative resistance of product layer = (TDmusion) /( 1.0m, )
DATA: 1 mol of oxygen at 273 K and l atm pressure occupies 22,400. cm}. p501“an = 4.13 gr cm'3 , Atomic Weight onn = 65.38. Atomic Weight ofS = 32.06
Reaction rate constant. k; = 2 cm sec"I Gas Dil‘fusivity in the ZnO layer Denatch : 0.08 cm2 sec‘I
From the above data you can estimate the molar density. page 8 of [0 pages \a 1* ‘
I 5; 0 0 I!) pugcs page to of 10 pages ...
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This note was uploaded on 04/28/2008 for the course MSE 217 taught by Professor Erb during the Fall '06 term at University of Toronto Toronto.
 Fall '06
 ERB

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