Set No. 1
Code No: RR3208 RR320802 02
III B.Tec B.Tech h II Semest Semester er Supplim Supplimen entar tary y Examin Examinati ations ons,, Aug/S Aug/Sep ep 2007 2007 CHEMICAL REACTION ENGINEERING-I (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
1. (a) Define Define reaction reaction rate constan constant. t. Develop Develop an express expression ion that facilit facilitates ates calcul calculaation of units of rate constant for any order. [6] (b) Determi Determine ne equili equilibri brium um conve conversi rsion on of A at 3730 K for the following aqueous reaction. k1
A⇀ ↽R k2
∆G0 = -3375 K cal/K mole
∆H r0 = -18,000 K cal/K mole Assu Assume me speci specific fic heat heatss of all all solu soluti tion onss are are equa equall to that that of water ater..
[10] [10]
2. (a) The decompo decomposit sition ion of ammo ammonia nia on a tungs tungsten ten wire wire is carrie carried d out at 856 8560 C and the following data are obtained. Total otal Pres Pressu sure re,, atm atm 0.30 0.3000 0.33 0.3300 0.35 0.3599 0.41 0.4188 Time, sec. 200 400 60 0 1 00 0 Check Check whether whether the reaction reaction follow followss zero order kinetics kinetics.. Find Find the reaction reaction velocity constant. (b) For a second second order reaction reaction show that the half life period is t = 1 / K C A0 K- is the rate constant and C A0 - init initia iall conce concent ntrat ratio ion n of reacta reactan nt. [8+8 [8+8]] 1 2
3. Thermal decomposition of hydrocarbon A proceeds to form R1 , R2 , R3 and R4 A
→
R1 + X
A+X Y
→
→
R2 + Y
R3 + X
X+Y
→
R4
Where X and Y are intermediate complexes. Determine the order of the decomposition of A from the ab ove mechanism. [16] 4. Methyl acetoxy propionate decomposes on heating to form methyl acrylate and acetic acid according to following stoichiometry. A=B+C The pyrolysis was found to be first order with k = 7.8 × 109 e−19,100/T (sec.−1 ). Where T in 0K . Calculate the volume of the plug flow reactor required to convert 78% of the reactant A with a flow rate of A being 1500 kg /hr at a pressure of 4 bar and 6000 C . The molecular weight of reactant is 146. [16]
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Set No. 1
Code No: RR3208 RR320802 02
5. At present the elementary liquid-phase reaction A + B → R + S takes place in a plug flow reactor using equimolar quantities of A and B. Conversion is 96%, C AO AO = C BO BO = 1 mol/litre. (a) If a mixed mixed reactor 10 times as large as the plug flow reactor reactor were hooked hooked up in series with the existing unit, which unit should come first and by what fraction could production be increased for that setup? (b) Does the concen concentrat tration ion level level of the feed affect the answe answer, r, and if so, in what way? Note: Conversion is to remain unchanged. [12+4] 6. For the solid catalyzed reaction A+B ← → R derive the expression for the rate of reaction if desorption of R is rate controlling. [16] 7. Deri Deriv ve the the energ energy y bal balan ance ce equ equati ation on for for an adia adiabat batic ical ally ly operat operated ed CS CSTR. TR.
[16] [16]
8. Write short notes on: (a) Order Order and molecul molecular ar (b) Empirical rate equations.
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Set No. 2
Code No: RR3208 RR320802 02
III B.Tec B.Tech h II Semest Semester er Supplim Supplimen entar tary y Examin Examinati ations ons,, Aug/S Aug/Sep ep 2007 2007 CHEMICAL REACTION ENGINEERING-I (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
1. (a) For the reacti reaction on 2A+ 12 B C write the relation between the rate of formation and disappea pearance of the three compo pon nents of the reaction. [6] →
(b) A reactio reaction n has the stoich stoichiom iometri etricc equation equation 2A the reaction.
→
R+ S what is the order of [2]
(c) The reaction with the following following stoichiometri stoichiometricc equation A+ 12 B R has the rate expression ?rA =kC AC B 0.5 . What is the rate expression for the reaction written as 2A + B 2R [2] →
→
(d) A certain reaction has a rate given by ?rA =0.005C A 2, mol/cm3 .min .min.. If the the concentration is to be expressed in mol/lit and time in hours, what would be the value and units of the reaction rate constant? [6] 2. Pure gaseous A decomposes decomposes to completion completion according according to the reaction A R + S in a then walled capillary tube which acts as a batch reactor. The required temperature is maintained in the tube by placing it into a bath of boiling water. The following data are obtained. Time (min.) 0.5 1 1.5 2 3 4 6 10 Length of Capillary o ccupied by 6.1 6.8 7.2 7.5 7.85 8.1 8.4 8.7 9.4 reactions reactions mixture(mm), mixture(mm), →
Find a rate equation in units of moles, liters and minutes for the decomposition. Pressure in the capillary measures 1000mm Hg guage. [16] 3. Experiment shows that the homogeneous decomposition of ozone proceed with a rate r03 = K [O3 ]2 [O2]−1 . Suggest a two step mechanism to explain this rate and explain how would you further test this mechanism? [16] −
4. (a) Assum Assumin ingg a stoich stoichio iome metry try A R, for a first order gas reaction, the size of plug flow reactor to get 99% conversion is 32 liters. If the stoichiometry is A 3 R. What is the required reactor volume? →
→
(b) The first order reaction A B is carried out in a tubular reactor in which volum volumetri etricc flow rate is constant. constant. Develo Develop p an equation equation relating relating the reactor reactor volume to the entering and existing concentration A, the rate constant k, and the volumetric flow rate υ . Determine the reactor volume necessary to reduce the existing concentration to 10% of the entering concentration, when the volumetric flow rate is 10 liters/min. and specific reaction rate k is 0.23/ min. [8+8] →
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Set No. 2
Code No: RR3208 RR320802 02
5. Substance A reacts according to second order kinetics and conversion is 95% from a single single flow reactor. reactor. We buy a second second unit identi identical cal to the first. For the same conversion, by how much is the capacity increased if we operate these two units in parallel or in series? (a) The reactors reactors are both plug flow. flow. (b) The reactors are both mixed flow.
[8+8]
6. (a) Describe Describe the the differen differentt types of cataly catalysts sts with with example examples. s. (b) Explain Explain the three mechanisms mechanisms by which which a reactant reactant adsorbed onto the catalyst catalyst surface is capable of reacting to form the pro duct. [10+6] 7. Deri Deriv ve the the energ energy y bal balan ance ce equ equati ation on for for an adia adiabat batic ical ally ly operat operated ed CS CSTR. TR.
[16] [16]
8. Write brief notes on (a) Isothermal Isothermal and non isothermal isothermal reactions (b) Semi batch reactors.
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Set No. 3
Code No: RR3208 RR320802 02
III B.Tec B.Tech h II Semest Semester er Supplim Supplimen entar tary y Examin Examinati ations ons,, Aug/S Aug/Sep ep 2007 2007 CHEMICAL REACTION ENGINEERING-I (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
1. (a) Define Define reaction reaction rate constan constant. t. Develop Develop an express expression ion that facilit facilitates ates calcul calculaation of units of rate constant for any order. [6] (b) Determi Determine ne equili equilibri brium um conve conversi rsion on of A at 3730 K for the following aqueous reaction. A
k1
⇀ ↽ k2
R
∆G0 = -3375 K cal/K mole
∆H r0 = -18,000 K cal/K mole Assu Assume me speci specific fic heat heatss of all all solu soluti tion onss are are equa equall to that that of water ater..
[10] [10]
2. For the reaction in in series A → R → S with k1 = k 2 , find the maximum concentration of R and when when it is reach reached ed in a batch batch reacto reactor? r? k1 and k2 are the rate constants for the first and second reactions. Show what happens if K1 = K2. [16] 3. Experiment shows that the homogeneous decomposition of ozone proceed with a rate −r03 = K [O3 ]2 [O2]−1 . Suggest a two step mechanism to explain this rate and explain how would you further test this mechanism? [16] 4. The decomposition of gaseous A proceeds as follows A → R (−rA) =
kC A 2
A tubular reactor of 2 liters volume is fed at 2 m3 /hr of pure A at 3000C and 20 atm. atm. Con Conve versi rsion on of reactan reactantt is 65%. In a commerc commercial ial plant, plant, it is desired desired to treat treat 100m3 /hr of feed gases at 40 atm and 3000 C containing 60%A and 40% diluents to obta obtain in 85% 85% con conversi ersion on of A. Find Find the the volum olumee of reac reacto torr requ requir ired ed.. [16] [16] 5. In a chemical factory factory five 10 liter tanks (CSTR) (CSTR) were found lying lying idle. The management decides to make use of these tanks for carrying out a first order liquid-phase reaction whose reaction rate constant is 2.0min−1 . The initial reactant concentration tion is 20.0 20.0 g mol/li mol/liter, ter, and the flow rate is 20 lit/min. lit/min. If they decide decide to operate operate the tanks in series and to obtain a fractional conversion of not less than 95% from the arrangement, will the tanks available in the factory be sufficient or will they have to order more such tanks? If so how many? [16] 6. For the solid catalyzed reaction A+B ← → R+S derive the expression for the rate of reaction if adsorption of B is rate controlling. [16] 7. Deri Deriv ve the the energ energy y bal balan ance ce equ equati ation on for for an adia adiabat batic ical ally ly operat operated ed CS CSTR. TR. 8. Write short notes on:
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[16] [16]
Set No. 3
Code No: RR3208 RR320802 02 (a) Homogeneous Homogeneous catalytic catalytic reactions. (b) Auto calahytic reactions.
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Set No. 4
Code No: RR3208 RR320802 02
III B.Tec B.Tech h II Semest Semester er Supplim Supplimen entar tary y Examin Examinati ations ons,, Aug/S Aug/Sep ep 2007 2007 CHEMICAL REACTION ENGINEERING-I (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) (a)
i. For For the reac reacti tion on 1/2 O +2N +2N O2 N 2O5 Write the relation between the rates of formation and disappearance of all the components involved in the reaction. [4] ii. Write the units of specific reaction rate constant in the eqn: rA =0. =0.08C 08C A 0.5 [2] iii. Define the molecularity of a reaction with an example [2] iv. Define elementary reaction with example [2] v. Define multiple reactions with example [2] →
−
(b) Sketch Sketch the energies involv involved ed in the transformation transformation of reactants reactants to products for exothermic and endothermic reaction. [4] 2. The reaction A+B R takes place in a constant volume batch reactor and first order with respect to component A and second order with reference to component B. Starting with C A = 0.6 mol/lit and C B = 1.8 mol/lit the following data are obtained obtained.. Derive Derive the integr integrated ated rate equatio equation n for the above above reaction reaction and find the reaction rate constant from the following data. [16] →
t, min C A mole/lit.
3.9 0.5
9.2 0.4
17.5 0.3
30.4 56 0.2 0.1
3. (a) Distinguish Distinguish between between elementary elementary and non elementary elementary reactions. reactions. (b) Show that the following following scheme scheme N 2 O5 ⇀ ↽ N O2 + N O3 N O2 + N O3 N O + O2 + N O2 N O + N O3 2N O2 is consistent with and can explain the observed first order decomposition of N 2 O5 . [4+12] ∗
∗
∗
∗
→
∗
→
4. Pure gaseous reactant A with C Ao millimole/litre is fed at steady rate Ao = 100 millimole/ into a mixed reactor, where it dimerizes, 2 A R with rate equation, rA = 2 (liter/m.m.hr) C A 2 . 60 % conversion takes place in this reactor, all else remaining unchang unchanged. ed. What will be the conversi conversion on if this reactor reactor is change changed d with,( with,(i) i) mixed mixed reactor, 5 times as large (ii) plug flow reactor of equal size. [16] →
−
5. Substance A reacts according to second order kinetics and conversion is 95% from a single single flow reactor. reactor. We buy a second second unit identi identical cal to the first. For the same conversion, by how much is the capacity increased if we operate these two units in parallel or in series? 1 of 2
Set No. 4
Code No: RR3208 RR320802 02 (a) The reactors reactors are both plug flow. flow. (b) The reactors are both mixed flow.
[8+8]
6. For the solid catalyzed catalyzed reaction A R derive the expression for the rate of reaction if desorption of R is rate controlling. [16] ← →
7. Deri Deriv ve the the energ energy y bal balan ance ce equ equati ation on for for an adia adiabat batic ical ally ly operat operated ed CS CSTR. TR.
[16] [16]
8. Write detailed notes on: (a) Temperature dependency of rate constant constant (b) Homogeneous reactions.
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