Download SGBAU B-Tech 7th Sem Chemical Engineering Chemical Reaction Engineering I Question Paper

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B.Tech. Seventh Semester Examination
11658 : Chemical Reaction Engineering -1 : 7 CH 02
AW - 3377

Time : Three Hours Max. Marks : 80

Notes:

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1. Answer three questions from Section A and three questions from Section B.
2. Due credit will be given to neatness and adequate dimensions.
3. Assume suitable data wherever necessary.
4. Diagrams and chemical equations should be given wherever necessary.

SECTION - A

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1. For irreversible reactions in series A -> R -> S
   Obtain the expression for
   t_max = ln(k₁/k₂) / (k₁ - k₂)
   and also for the maximum concentration of R.
   OR
   

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   Aqueous A at a concentration C_A0 =1 mol/liter is introduced into a batch reactor where it reacts away to form product R according to stoichiometry A -> R . The concentration of A in the reactor is monitored at various times, as shown below:
   t, min 0 100 200 300 400
   C_A mol/m³ | 1000 500 333 250 200
   For C_A0 =500mol/ m³ find the conversion of reactant after 5 hours in the batch reactor.
2. Obtain the relation between concentration, time and rate constant for the Autocatalytic reactions. Plot conversion - time and rate- concentration curves for autocatalytic reaction.
   

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   OR
   The following data are obtained at 0° C in a constant - volume batch reactor using pure gaseous A:
   Time, min 0 2 4 6 8 10 12 14 ∞
   Partial pressure of A, mm | 760 600 475 390 320 275 240 215 150
   The stoichiometry of the decomposition is A -> 2.5R. Find a rate equation which satisfactorily represents this decomposition.

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3. Find the first-order rate constant for the disappearance of A in the gas reaction 2A -> R if, on holding the pressure constant, the volume of the reaction mixture, starting with 80% A, decreases by 20% in 3 min.
   OR
   Find the first-order rate constant for the disappearance of A in the gas reaction A -> 1.6R if the volume of the reaction mixture, starting with pure A increases by 50% in 4 min. The total pressure within the system stays constant at 1.2 atm, and the temperature is 25° C.

SECTION - B

1. Derive performance equations for plug flow reactor. Explain graphically the representation of the performance equation for plug flow reactor.
   

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   OR
   A gaseous feed of pure A(1 mol/liter) enters a mixed flow reactor (2 liters) and reacts as follows:
   2A -> R, -r_A =0.05C_A² mol/liter - sec
   Find what feed rate (liter/min) will give an outlet concentration C_A = 0.5 mol/liter.
2. Liter/s of a 20% ozone - 80% air mixture at 1.5 atm and 93°C passes through a plug flow reactor. Under these conditions ozone decomposes by homogeneous reaction.
   

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   2O₃ -> 3O₂, -r_ozone =kC²_ozone
   k =0.05 liter/mol-s
   What size reactor is needed for 50% decomposition of ozone?
3. We plan to replace our present mixed flow reactor with one having double the volume. For the same aqueous feed (10 mol A/liter) and the same feed rate find the new conversion. The reaction kinetics are represented by
   A -> R, -r_A =kC_A³
   

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   and present conversion is 70%
   OR
   Explain the size comparison of single reactors, mixed versus plug flow reactors, for first and second order reactions.
4. The kinetics of the aqueous-phase decomposition of A is investigated in two mixed flow reactors in series, the second having twice the volume of the first reactor. At steady state with a feed concentration of 1 mol A/liter and mean residence time of 96 sec in the first reactor, the concentration in the first reactor is 0.5 mol A/liter and in the second is 0.25 mol A/liter. Find the kinetic equation for the decomposition.
   OR
   

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   Consider the autocatalytic reaction A -> R, with -r_A =0.001 C_AC_R mol/liter-s. We wish to process 1.5 liters/s of a C_A0 =10mol/liter feed to the highest conversion possible in the reactor system consisting of four 100-liter mixed flow reactors connected as you wish and any feed arrangement. Sketch your recommended design and feed arrangement and determine C_A from this system.

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