111111011 2 3 B.E. / B.Tech. (Chemical Engineering)

Seventh Semester (CGS)

Chemical Reaction Engineering - I

P. Pages : 7 7 CH 02 / 7 CT 02 Time : Three Hours Max Marks : 80

Note : 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. Diagrams and chemicals equations should be given wherever necessary.

4. Illustrate your answer necessary with the help of neat sketches.

5. Discuss the reaction, mechanism wherever necessary.

6. Use of pen Blue/Black ink/refill only for writing the answer book.

SECTION - A

1. a) What is the Rate of chemical reaction ? Give the factors affecting rate of chemical reaction. 5

b) For a gas phase reaction at 400k, the rate is reported as 8

t

dPAit

_ 3.66 PA au" h

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a) What are the units of rate constant ?

b) What is the value of rate const. for this reacn if the rate equation is written as

-1 dNA 2 rA = =

k CA. mol/(f.h)

ii) -TA = k CA, mo143 .4

OR

2. a) Differentiate between molecularity & order of reaction with example. 6

12. a) Prove that,

_ CPAT )C A -AHR for an adiabatic reacn condition.

b) What reacn schemes and conditions would you use to have maximum concentration of R for the following parallel reactions ? 6

A + B -*R(desired)r B = 15.e273/1- CA5 -CB

A + B -> S(undesired)r s = 200. e2"/T CA CB

b) Concentration V/S time data for the reaction is given below. 7

A --+ R

B -*S

Time (h) Concentration Concentration ofAmol/I ofRmo1/1

0 0.00 0.100 0.050 0.050

10. A Gas mixture consisting of 50 mol% A and

50 mole % inerts at 10 atm enters the reactor

with flow rate of 6( is at 144C. 13

The laboratory measurements of the rate as

a function of conversion at 144 C and 10 atm

are :

0.1 02 [ 0.3 1 0.4 rX1 0

rA 0.0053 0.0052 0:005 0.0045 0.004

-- 0.5 0.6 0.7 0.8 0.85

0.0033 0.0025 0.0018 0.00125 0.001

If the reaction is carried out in two reactors in

series with 40% conversion in the first reactor

and 85% overall conversion, estimate the total

volume of the two reactor when (i) the reactors

are both mixed flow (ii) the reactors are both

plug flow.

11. a) Discuss the optimum temperature progression in detail. 7

b) Obtain the expression for equilibrium conversion at adiabatic condition. 7

OR

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Time Concentration Concentration (h) of 8 mol i I of R moll I

0

0.10

0.00 2 0.075

0.025

i) Which reaction proceed at the greatest rate?

ii) What are the rates of formation of R and 5?

3. a) Derive expression for temperature dependency of reaction rate constant from Collision Thew 8

b) The rate const. of certain reaction are

1.6 x10-3 and 1.625x 10-2 S -1 at 10C &

30C. Calculate the activation energy. 5

OR

4. a) Compare the Collosion Theory and Transition State Theory with Arrehenius Law. 4

b) At 500 k the rate of bimolecular reacn is ten times the rate at 400k. Find the activation energy for this reaction. (a) From Arrhenius Law (b) from collision theory (c) What the percentage difference in rate of reaction at 600k predicated by these two methods ? 9

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3 P.T.O.

5. Derive the desired integrated rate equation for

second order reacn with CA0 7 CB in terms

of concn & conversion. 14

OR

6. An aqueous soln of ethyl acetate is to be saponified with NaOH. The initial concn of

ethyl acetate is 59/i and that of caustic is

0.1 normal. The values of second order rate const. at 0C and 20C are k = 0.235 & 0.924

mol)(min) -l resP. The reaction is

irreversible. Calculate the time required to saponify 95% ester at 40C. 14

SECTION - B

7. a) Design a performance equation for steady state plug-flow reactor for

i) constant density system (E A = 0)

ii) variable density system (E A x 0) 8

b) In an isothermal batch reactor the conversion of liquid reactant A is 70% in 13 min. Find the space time and space velocity necessary to effect this conversion in a plug flow reactor and in a mixed flow reactor. Consider first order kinetics. 5

OR

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i) We are planning to operate a mixed reactor to convert A into R. This is a liquid reacn

with the stoichiometry A R . The rate of reaction is given below. What size of mixed flow reactor is needed to achieve 75% conversion of feed stream of 1000 mol Alb

with CA 0 =1.2mol/f ?

ii) Repeat part (i) with the modification that the feed rate is doubled, hence 2000 mol

Ath with CA0 = 1.20mol/ e are to be treated.

iii) Repeat part (i) with the modification that 1000 mol A/h are still to be treated, but

with CA0 = 2.4 mol / f down to

CA/ = 0.30 molt( . 13

9. a) Derive the equation for N-equal size GSTRS connected in series in terms of concentration and conversion. 8

b) Discuss the size comparison of CSTR with PFR for nth order reaction.

OR

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5 P.T.O.