CONFIDENTIAL 2 EH/JUN 2014/CHE584/594

QUESTION 1

(P01, C01, C02, C2, C3)

a) Chemical reaction can be divided into homogeneous and heterogeneous reaction. Definehomogeneous and heterogeneous reaction, and explain factors that could influence theirrate of reaction.

(8 marks)b) The following decomposition reaction

c) proceeds at temperatures below 100C. The temperature dependence of the first-orderrate constant has been measured. The experimental data are summarized below:

T (K)288298313323338

1.04 x10's3.38 x10's2.47 x 10-47.59 X 10-44.87 X 10.3

d) Using an appropriate approach, determine the activation energy, E and pre-exponentialfactor, A for this decomposition reaction.R is given as 1.9872 cal mol-1 K-1.

(12 marks)

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CONFIDENTIAL 3 EH/JUN 2014/CHE584/594

QUESTION 2

(P01, C01, C2, C3)

An elementary reaction was carried out in a sealed beaker and placed into a constanttemperature bath at 412 K. After various reaction times, the beaker was removed and quicklycooled to room temperature to stop the reaction. The chemical reaction equation can bedescribed as follows:

2A ~ product

From the amount of product collected, the conversion was recorded in table below:

Time (min) Conversion (%)5132534455980100120

4.911.220.425.631.636.745.350.755.2

Given the initial concentration of A was 0.2 M.

a) If these data consistent with second order reaction rate, determine the rate constant, k.

(10 marks)

b) Construct a stoichiometric table for this reaction. Determine the rate of reaction if thereaction achieves 90% conversion.

(6 marks)

c) Suggest time required for this reaction to achieve 90% conversion.(4 marks)

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CONFIDENTIAL 2 EH/DEC 2013/CHE5841594

QUESTION 1

(P01, C01, C1, C2, C, C4)

a) An undergraduate student conducted an experiment in a laboratory, as part of hiscourse requirement, to study the kinetics of a reaction of two unknown reactants, Aand B. The instructor informed him that the reaction was according to thestoichiometric equation of A + B -7 products. The recorded experimental data was asfollows:

Table 1. Reaction rates of a reaction A and B.

Concentration of A, CA(moIlL)

Concentration of B, CB(mollL)

Reaction Rate, -rA(moIlL'min)

3.03.04.5

187.596.096.0

754872

Determine the reaction orders with respect to A and B and hence, determine theoverall order of the reaction.

(8 marks)

b) The stoichiometric reaction of reactants A and B is as follows:

A+B-7C+D

The liquid-phase reaction is first order with respect to A and B. The rate constant, k,of this reaction is equal to 0.0017 m3lkmol'min at 188C with an activation energy, E,of 47,166 kJlkmol. The initial entering concentrations of A and Bare 1.8 and 6.6kmol/m3, respectively. Given the universal gas constant, R, as 8.314 kJ/kmolK.

i) Express the rate law for the rate of disappearance of A, -rA, in terms ofconcentration.

(2 marks)

ii) Set up a stoichiometric table for this reaction and express -rA, in terms ofconversion (XA).

(10 marks)

iii) Calculate the initial rate of reaction (XA = 0) at 188C and 25C.(7 marks)

iv) Determine the rate of reaction at 90% conversion at 25C.(3 marks)

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CONFIDENTIAL 3 EH/DEC 2013/CHE584/594

QUESTION 2

(POS, C02, C3, C4)

Some of the uses of ethylene glycol are for antifreezing and the manufacturing ofpolyesters. A laboratory-scale batch reactor which operates isothermally has producedethylene glycol (MW = 62 kg/kmol) from the mixing of 500 mL of a 2 M solution of ethyleneoxide in water with 500 mL of water (containing a very small amount of catalyst). Thereaction is first-order with respect to ethylene oxide. Assuming the concentration of water isconstant during the course of the reaction, the concentration of ethylene glycol is recordedas a function of time as given in Table 2.

C2H40ethylene oxide

(A)

H20~ C2H602

ethylene glycol(C)

Table 2. Concentration-time data of ethylene glycol.

Time (min) Concentration of ethylene glycol(mol/L)0.00.51.01.52.03.04.06.010.0

0.0000.1450.2700.3760.4670.6100.7150.8480.995

Use an appropriate method to determine the rate constant, k, of the reaction.(20 marks)

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CONFIDENTIAL 2 EH/JUN 2013/CHE584/594

QUESTION 1

(P01, C01, C3, C4, C1)

Gas phase reaction was carried out in an isothermal batch system to form nitrogenmonoxide and water according to the reaction equation:

4NH3 + 502 -+ 4NO + 6H20

An equal molar of NH3 and O2 are fed to the reactor with total pressure 4.7 atm and 300Cas reaction temperature. With respect to NH3 as the limiting reactant, the followingexperimental data were recorded from constant batch reactor volume

I 1 E h b hTabe xoenmenta data in an isot ermal atc systemT (min) 0 50 100 150 200 250 300

PNH3 2.35 1.78 1.44 1.20 1.04 0.916 0.817

Rate law of the above reaction respond to -rA= kCAOCSi3, in which 13 is zero order withrespect to oxygen. Given R (gas universal constant) as 0.082 atrn-drn-mol+K",

a) Construct a stoichiometric table for this gas phase reaction in constant batch reactorvolume.

(4 marks)

b) Determine the reaction order, a and the rate constant, k using numerical(differentiation) method.

(13 marks)

c) Write the rate of law by taking into account the stoichiometric of this reaction.(3 marks)

QUESTION 2

(POS, C02, C3)

The dimerization of propylene into isohexane in which the reaction is 2A ~ P. The gasreaction was conducted in a variable-volume batch reactor at constant pressure. Thereaction was first order and initially consists of 70 mol% of A and the balance inert. Theamount decreased by 20% in 4 min. Based on the given information, determine thefollowing:

a) The fractional change in volume, SA for complete conversion.

b) Conversion of propylene.(3 marks)

(5 marks)c) Rate constant, k of the reaction.

(12 marks)

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CONFIDENTIAL 2 EH/JAN 2013/CHE584/594

QUESTION 1

(POi, COi, C2, C3)

a) Explain with examples the terms 'elementary' and 'non-elementary' reactions.(5 marks)

b) Naphthalene, which is the most abundant component of coal tar is the liquid residueformed during the distillation of coal into coke. Naphthalene is commonly used as araw material in the production of phthalic anhydride. Naphthalene vapours are easilyburn when mixed with air and its gas phase reaction is elementary and reversible asfollows,

An equal molar of ClOHs and O2 are fed to the reactor at a pressure of 10 atm and200C

i) By taking C10Hs as a basis, construct a complete stoichiometric table for thisreaction if the reaction occurred in a flow system.

(5 marks)

ii) If the conversion of C10Hs is 75%, determine the final concentration of CO2 anddetermine the rate of reaction as a function of conversion

(7 marks)

iii) Express the rate of reaction as a function of conversion if this reaction is carried outin a constant volume system.

(3 marks)Given:

QUESTION 2

(P05, C02, C3, C4)

a) The following reactions occur in parallel to produce Y and Z with respective rateequations:

The reactions take place in two mixed flow reactors arranged in series. The feed to thefirst reactor contains A and Z with initial concentrations of 1 mollL and 0.3 mollLrespectively. From experimental results, it is found that the space time for first reactor is3 minutes with concentrations of CA1 to be 0.3 mol/L, CY1 of 0.2 mollL and CZ1 of

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0.7 mollL. If the space time for second reactor is 12 minutes, determine the exitconcentration of A from the second reactor.

(8 marks)

b) In a continuous stirred tank reactor (CSTR), an irreversible liquid phase reaction is to becarried out according to the reaction:

A--,>B+C

Pure A enters the reactor at a concentration of 2.5 mol/dm". The experimental dataare measured which relates the variations in r and CA.

T bl 1 Ea e xoerirnenta ata or CSTRRun 1 2 3 4 5,(min) 15 38 100 300 1200CA.mol/drn") 1.5 1.25 1.0 0.75 0.5

Id f

i) Identify the relationship between the space time, , and concentration of A, CA bystating the necessary assumption(s).

(2 marks)

ii) Determine the rate of reaction and the volume of CSTR required if desiredconversion of A is 0.80. Given that the feed flow rate is 150 mol/min.

(9 marks)

QUESTION 3

(P05, C03, C3, C4)

In a constant batch reactor, an irreversible gas-phase non-elementary reaction of:

A+ 2B ~ C

is to be carried out isothermally and the changes in pressure is considered negligible. Thegas mixtures enters the reactor at temperature of 260C and pressure of 1013 kPa, withmolar composition of 30% A and balance B. Data taken from laboratory experiments are asfollows:

T bl 2 E t Id t f h t t b t h ta e xoenrnen a aa or gas-pi ase cons an ac reac or-rA' x 10''>

0.01 0.085 0.005 0.0035 0.002 0.0015 0.001(moVka.min)

Conversion, XA 0.0 0.1 0.2 0.3 0.4 0.5 0.6

The volumetric flow rate of the feed is 10 m3/min and assuming the density of feed to be1 kg/m3, Using numerical method,

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CONFIDENTIAL 2 EH/JUN 20121CHE584/594

QUeSTION 1

(P01, C01, C2, C3)

Ethyl benzene is an important intermediate mainly used for the production of styrene. Ethylbenzene can be produced by reacting ethylene and toluene as follows:

2 Ethylene + Toluene -+ Ethyl benzene + Propylene

The above reaction takes place isothermally without a pressure drop with entering pressureand temperature of 8.1 atm and 225C, respectively. The feed gas consists of 30% tolueneand 70% ethylene. By assuming that the reaction is elementary,

a) Construct a stoichiometric table to determine the concentrations of each of thereacting species.

(12 marks)

b) Detennine the rate of reaction as a function of conversion, X and the rate constant,k.

(4 marks)

c) State three ways of how reacting substances could lose their chemical identity andsuggest which from these ways ethylene and toluene could lose their chemicalidentity to produce ethyl benzene and propylene.

(4 marks)

QUESTION 2

(POS, C02, C3, C4)

The below equation represents a liquid phase reactionA+B--tC

A and B streams ~5 dm3/min and concentration of 2M each) are mixed before entering areactor. A 800 dm PFR is operated at 300K (cannot be heated or cooled) and a 200 drrr'CSTR (can be heated to 7rC) is planned to be used to react A and B isothermally in liquidphase to produce product C. Note that k=0.07 dm3/mol.min at 300K and E=20 kcaLlmol.

a) Suggest which reactor and under what conditions do you recommend? Explain thereason of your choice.

(12 marks)

b) Determine the time it takes to achieve 90% conversion in a 200 dm3 batch reactor(BR) with CAo==Cso ~ 1M after mixing at temperature of 7rC?

(4 marks)

c) Evaluate your answer to part (b) be if the reactor were cooled to OC

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(4 marks)CONFIDENTIAL

1-

CONFIDENTIAL 2 EH/APR 2011/CHE5841594

QUESTION 1

(P01, C01, C3, C4)

Industrial butadiene which has been used to produce synthetic rubber can be obtained bythe dehydrogenation of butenes through Chromium (Ill) Oxide (Cr203). A process engineerwas asked to study the specific dehydrogenation of butenes. The reaction was carried out ina continuous stirred tank reactor (CSTR) and in first order. The laboratory data taken showsin Table 1.

0.00180 0.00355 0.00717323.0 328.0 333.0

i) Calculate the activation energy and specific rate of reaction.ii) Determine the reaction rate if the reaction was carried out at 500 K.

(15 marks)

QUESTION 2

(P01, C01, C3, C4, C5)

Naphthalene is a white solid that evaporates easily. It is also called mothballs, moth flakes,white tar, and tar camphor. When mixed with air, naphthalene vapors easily burn. The gasphase irreversible reaction is elementary, following: .

C10He + 1202 ~ 10C02 +4H20An equal molar of C10HS and O2 are fed to the reactor at a pressure of 15 atm and 250C.

Additional information:

k = 20 dm3

CfoHa mol. s

a) Set up a complete stoichiometric table for this reaction if the reaction occurred in a flowsystem by taking C10Heas a basis. .

(10 marks)

b) If the conversion of C10Hs is 70%, find the final concentration of CO2 Determine the rateof reaction as a function of conversion

(10 marks)

c) Suggest the rate of reaction as a function of conversion if this reaction is carried out in aconstant volume system.

(3 marks)

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CONFIDENTIAL 2 EHlOCT 2010/CHE5841594

QUESTION 1

For the following reactions, derive the outlet concentrations of reactant A.

a) A constant temperature and pressure gas phase reversible reaction of 2A 2C, whichpure A is fed to the reactor.

b) For an isothermal gas phase irreversible reaction 3A ~ C, which pure A is fed to thereactor.

c) A constant temperature and pressure gas phase reversible reaction A ~ 3D, which pureA is fed to the reactor.

d) An isothermal gas phase reversible reaction 2A + 28 ~ 2C, with 2 moles of A and amole of B fed to the reactor.

e) For an isothermal gas phase reversible reaction 3A ~ 2C, which pure A is fed to thereactor.

(10 marks)

QUESTION 2

Heating of nitrosyl chloride above 1OO"C will decompose It to the following reaction.

2 NOCI ~ 2 NO + CI2

In order to study the rate of this reaction, relevant data was collected and studied at 200"C.The concentration initially consisting of NOCI only changes as given in Table 1.

Table 1 Concentration of NOCI- time datat (s) 0 200 300 500Concentration of

0.0200 0.0159 0.0144 0.0121NOCI (mole/l)

Determine the order of the reaction and the rate constant, k, in Lfmol.s.(20 marks)

QUESTION 3

For the gas phase reaction C2H4 + C~H6 ~ C6H10 which is carried out isothermally inconstant volume batch reactor. The rate law of the reaction is

7 [-115,000J- rc H = 3.0x 10 exp Cc H Cc H1 RT 1 4 6

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CONFIDENTIAL 3 EH/OCT 2010/CHE5841594

With,R = 8.314 J K''mor", Arrhenius parameters A and EA in L mol' S1 and J mar" respectively.Given the rate disappearance of ethylene, C1H4 is 8x10';' mol L1Sl.

a) Find the temperature, T in Kelvin would be to achieve 57.6% conversion of reactants.Please note that the reactants initially are in equimolar ratio, time required to achieve57.6% conversion is 4 min.

(10 marks)

b) Using the same temperature as in part (a), find the time required for 75.4% conversion of1,3~butadiene, C4Hs, if the reaction is carried out isothermally.

(5 marks)

c) Find the total initial pressure for this gas reaction using the same temperature as in (a),with R = 8.314 L kPa K'lmol,l.

(5 marks)

QUESTION 4

a) List three assumptions in arriving at the following expression (1) for a CSTR with heattransfer.

... (1)

Given that expression (1) is derived from the General Energy Balance over a continuousreactor which can be written as expression (2) below.

...(2)

(3 marks)

b) A first-order, liquid-phase endothermic reaction A 78 + C, is conducted in a CSTR of15 m3 volume operating at steady-state. The feed temperature is 310 K. But, the reactoris heated in order to increase the rate and achieve a conversion of 75%.

i) Determine the rate of reaction needed to achieve this conversion.(5 marks)

ii) Determine the temperature needed to achieve this conversion.(5 marks)

iii) Determine the heat transfer requirement of the reactor to achieve this conversion.(7 marks)

Given:Arrhenius constant, A = 3.5>