mse217s_2009_exam - University of Toronto Department...

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Unformatted text preview: University of Toronto Department ofMaterials Science and Engineering Kinetics Section of MSE-217H182 “FINAL EXAMINATION Friday April 17th 2009, 14:00—16:30 WRITE USING CAPITAL LETTERS FIRST NAME: LAST NAME: l STUDENT NUMBER: ' SIGNATURE: ANSWER ALL FOUR PROBLEMS Examiner : Professor Stavros A. Argyropoulos l Marks Problem 1 Problem 2 Problem 3 Problem 4 Total page 1 of 13 pages PROBLEM I ( MARKS 25 ) Aqueous A reacts to form B according to the following reaction ( A —> B ) and in the first minute in a batch reactor its concentration from the original concentration Of CAO : t0 CAf: AA) Find the rate constant for the reaction if the kinetics is first order with respect to A. B) How long it will take the reactant A to reach XA = 0.95 . page 2 of 13 pages, page 3 of 13 pages, page 4 of 13 pages PROBLEM 2 ( MARKS 30 ) The liquid phase irreversible reaction A —> B + C is carried out in a mixed flow reactor. To learn the rate law the volumetric flow rate Do, (hence r=—) is varied U0 and the effluent concentrations of species A recorded as a function of the space time T . Pure A enters the reactor at a concentration of CA0 = 2 mol/lit. Steady state conditions exist when the measurements are recorded. Run Number 1 2 3 I 14.8 100 1200 CA(mol/1it) 1.5 1.0 0.5 Determine the reaction order _, n , and the specific reaction rate kA. page 5 of 13 pages page 6 of 13 pages PROBLEM 3 ( MARKS 30 ) Spherical particles of Zinc Sulfide, ZnS, of size R=l mm are roasted in a gas stream containing 8 molar % Oxygen at 900 0C and 1 atm. The stoichiometry of the reaction is: 2ZnS+302—>2Zn0+2802 A) Calculate the time needed for 75% conversion of a particle assuming: 1. The gas stream diffusion through the ZnO controls and 2. The surface reaction controls B) Estimate the relative resistance of ZnO product layer assuming complete conversion of the particle. Assumptions 1) The above reaction proceeds by the shrinking core model, 2) The gas film resistance can be neglected since the ZnO growing product layer is present, 3) The gas stream follows the ideal gas law. W Ttotal : TDiffusion + TChemical Reaction 2) Relative resistance of product layer = (TDiffusion) /( ‘Etotal ) DATA: 1 mol of oxygen at 273 K and 1 atm pressure occupies 22,400. cm3. psolid Zns = 4.13 gr cm‘3 , Atomic Weight onn = 65.38, Atomic Weight of S = 32.06 Reaction rate constant, kS = 2 cm sec‘1 Gas Diffusivity in the ZnO layer Deffective = 0.08 cm2 sec". page 7 of 13 pages page 8 of 13 pages page 9 of 13 pages page 10 of 13 pages PROBLEM 4 ( MARKS 15 ) A spherical particle undergoes the following reaction: Mg) + b 13(8) —> R(g) + 3(8) This particle has radius R=1 cm. Previous visual examinations suggested the above reaction follows the Shrinking Core Model (SCM). In addition it was also found that reaction resistance of gas at the unreacted core controls. The experimentation has shown that the radius of the unreacted core was 0.5 cm after 15 min from the starting time of reaction. Estimate the time needed to complete the reaction under the above mentioned conditions. page 11 of 13 pages page 12 of 13 pages page 13 0f 13 pages ...
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This note was uploaded on 01/28/2010 for the course MSE 217 taught by Professor Erb during the Spring '06 term at University of Toronto- Toronto.

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mse217s_2009_exam - University of Toronto Department...

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