sathyabama university

Register Number
(Established under section 3 of UGC Act,1956)
Course & Branch :B.Tech - BTE
Title of the Paper :Chemical Reaction Engineering
Sub. Code :SCHX1012 (2010-11)
Date :19/11/2012
Max. Marks:80
Time : 3 Hours
Session :FN
Answer ALL the Questions
State the law of mass action.
(10 x 2 = 20)
Write the Vant Hoff equation showing the temperature
dependency of equilibrium constant.
Define space and space velocity.
Determine the fractional change in the volume of the reaction
system A → 3R (Input condition: 60 mole % A and 40 mole %
Give the classifications of multiple reactions with suitable
Show graphically how CSTR’s in series approximate a PFR.
What are the reasons for non-ideality in real reactors?
Define vessel dispersion number and give its significance.
Explain shrinking core model.
10. Define rate limiting step in the chemical process?
(5 x 12 = 60)
Answer All the Questions
11. Explain the temperature dependency of rate equation by
Arrhenius, Collision and Transition state theories.
12. (a) The pyrolysis of ethane proceeds with an activation energy of
about 75000 cal/mol. How much faster is the decomposition at
650 oC than at 500 oC.
(b) At 500 K the rate of a bimolecular reaction is ten times the
rate at 400 K. Find the activation energy for this reaction
(i) From Arrhenius law
(ii) From Collision theory
(iii) What is the % difference in rate of reaction at 600 K
predicted by these two methods?
13. Derive the performance equations for Batch reactor, PFR and
14. The decomposition of NH3 on tungsten wire at 856 oC yielded the
following results
Time, sec
200 400 600 1000
Total pressure, (torr)
228 250 273 318
Find the order of the reaction and the rate constant.
15. A homogeneous liquid phase reaction with the stoichiometry and
the kinetics A → S, -rA = kCA2 takes place with 50% conversion
in a MFR.
(i). Find the conversion if this reactor is replaced by another MFR
having volume 6 times that of the original reactor – all else
remains unchanged.
(ii). Find the conversion if the original reactor is replaced by a
PFR of the same size – all else remains unchanged.
16. The elementary liquid phase reaction A+B → R+S is carried out
in a PFR. For equimolar amounts of A and B (CAo= CBo = 0.9
mol/l), 94% conversion is achieved in it. If a CSTR, 10 times as
large as the PFR, were arranged in series with the existing unit,
which unit needs to be arranged first (in series) to enhance the
production rate?
17. (a) Derive the equation to find out the conversion using
dispersion model.
(b) Explain the method of conducting stimulus response
18. The concentration readings in table represent a continuous
response to a pulse input into a closed vessel which is to be used
as a chemical reactor. This reactor is used for a liquid
decomposing with rate -rA = k CA, k = 0.1 min-1
Time, min
0 1 2 3 4 5 6 7 8 9 10 12 14
Tracer conc., g/m3 0 1
8 10 8 6 4 3 2.2 1.5 0.6
Calculate (a) the conversion using
(i) Real reactor
(ii) Ideal PFR,
(iii) Ideal MFR and
(iv) The tanks in series model.
(b) Assume dispersed plug flow in a closed vessel, find out vessel
dispersion number.
19. Explain the determination of surface area and pore volume of the
20. Derive the rate equation for non-catalytic chemical reaction when
diffusion through ash layer is controlling the rate of reaction.