••

L-2rr-l/CHE Date: 05/0112015

BANGLADESH UNIVERSITY OF ENGlNEERlNG AND TECHNOLOGY, DHAKA
L..2ff-1 B. Sc. Engineering Examinations 2013-2014

Sub: CHE 201 (Material and Energy Balance)

Full Marks: 210 Time: 3 Hours

USE SEPARATE SCRlPTS FOR EACH SECTION
The figures in the margin indicate full marks.
---_._ ..
"'" ._ .._----- -----_ ..
_-- _- -------_ ...._-
-------_ .... ._- ._--------_ ..

SECTION-A
There are FOUR questions in this section. Answer any THREE.
ChE 111/201 Data Booklet is supplied.

1. n-Hexane is used to extract oil from soybcaI15. The solid residue from the extraction
unit, which contains 0.75 kg liquid hexane/kg dry solids, is contacted in a dryer with
nitrogen that enters at 85"C. The solids leave the dryer containing 0.05 kg liquid
hexane/kg dry solids, and the gas leaves the dryer at 80°C and 1.0 atm with a relative
satl.lfation of 72%. The gas is then fed to a condenser in which it is compressed to 5.0
atm and cooled to 28"C, enabling most of the hexane to be recovered as condensate ..
(a) Calculate the fractional recovery of hexane (kg condensedlkg hexane fed in wel

solids). (18)
(b) A proposal has becn made to split the gas stream leaving the condenser, combining
90% of it with fresh make-up nitrogen, heating the combined stream to 85"C, and
recycling the heated stream to the drycr inlet. What fraction of fresh nitrogen

required in part(a) would be saved by introducing the recycle? (11)

2. (a) Powdered milk produced in a spray dryer 6 m in diameter by 6 m High. Air enters at
the bottom of the dryer at 167"C und -40 em HlO glluge pressure, Liquid milk is
sprayed from the top of the dryer cvntains 70% water by mass, all of which evaporates
and leaves the dryer as wet gas. This weI gas contains 12% (mole) water and leaves
[rom the top ofilie dryer at 83"C and 1 atrn (absolute) at a rate of311 m'/min. Calculate
the production rate of dried milk and the volwnemc flow rate of the inlel air. Estimate

the upward velocity ohir (m/s) at the bottom of the dryer. (20)
(b) A mixture of liquid, 60 mole% n-hexane and 40 mole% n-heptane, is in equilibrium
with its associated vapor at 1 atm. Calculate thc value of Tbpand the equilibrium vapor

composition. State assumptions, if any. (15)

3, Methanol is synthesized from carbon monoxide and hydrogen in a catalytic reactor. The
fresh feed to the process contains 32 mole% CO, 64 mole% H2 and the halance N2. This

Conld PI2

I'"
CHE201lCHE
Could ... Q. No.3

stream is mixed with a recycle stream in a ratio 5 mole recyclell mole fresh feed to
produce the feed to the reactor, which contains 13% N2• A low single pass conversion is
attained in the reactor. Th~ reactor effluent goes to a condenser from which two streams
emerge: a liquid product strewn containing essentially all the methanol formed in the

reactor, and a gas stream containing all the CO, H2, and N2 leaving the reactor. The gas
stream is split into two fractions: one is removed as a purge stream and the other is
recycle stream that combines with the fresh feed to the reactor. Calculate the production
rate of methanol (mollh), the molar flow-rate and composition of the purges gas, and the
overall and single pass conversion, What are the reasons for using recycle and purge

streams? (35)

4. (a) Ethane is burned with 3Q% excess air. The percentage conversion of the ethane is
85%. Of the ethane burned 30% reacts to form CO and the balance reacts to form COl.
Calculate thc molar composition of the stack gas on a dry basis, and the mole ratio of

water to dry stack gas. (17)

(b) The air in a building is to bc maintained at 25"C and 55% relative humidity hy
passing outside air through a water spray. The air enters the spray chambcr at 32"C and
75% relative humidity, leaves the chamber cooled and saturated with water vapor, and is
then reheated to 25°C for delivering it into the building. Estimate the temperature of the
air leaving the spray chamber and the water (kg) added to or removed from each kg of

dry air processed. (18)

SECTION -B
There are FOUR questions in this section. Ans'Wer any THREE.

5. (a) An air conditioner cools 226 mJ/min of humid air at 36°C and 98% relative humidity

to 10°C. Calculate the rate of water removal in the unit and the cooling duty in tons

(I ton = ]2,000 Btulh) (20)

(bl Au aqueous ammonia solution cllnlains 30 wt% NHJ. (15)

(i) Use the enthalpy-concentration diagram for the ammonia-water system at I atm
to determine the mMS fraction ofNHJ in the vapor that would be in equilibrium
with this solution in a dosed flask at I arm and the corresponding system
temperature (see Figure for Question 5(b)).
(ii) If the liql.lid in (i) accounts for 90% of (he total system mass, calculate the

overall system composition and specific enthalpy using balances.

Conld PI3
 =3=

CHE20llCHE

6. Methane at 25°C is bwned in a boiler furnace with 10% excess air preheated to 100"C.
Ninety percent of the methane fed is consumed, the product gas contains iO mol
C02/mol CO, and the combustion products leave the furnace at 400"C. (35)
(i) Calculate the heat transfcrred from the furnace, -Q(kw), for a basis of 1000
mol Cl-4 fedls.
(ii) Would the following changes increase or decrease the rate of steam
production? (Assume the fuel fecd rate and the fractional conversion of the C}4
remain constant)
-Increasing inlet air temperature.
_ Increasing the stack gas temperature
_ Increasing the mole ratio ofCO~ to CO formation in the furnace.

7. Ethanol is produced commerdaliy by the hydration of ethylene: (35)

Some of the product is convcrted to diethyl ether in the lUtdesirableside reaction

The combined fecd to the reaculr contains 53.7 mol% C~H4,36.7% H20 and the balancc
N2 which enten; the reactor at 310"C. The reactor operates isothermally at 310"C. An
ethylene conversion of 5% is achieved and the yield of ethanol (moles ethanol
produced/mole ethylene consumed) is 0.900.
Data for Diethyl Ether:
~H~ = -272.8 kJ/mol for the liquid

~H, = 26,05 kJ/mol (independent ofT)

Cp [kJ/(mol.°C)] '" 0.08945 + 40.33 x 10-5 TCC) - 2.244 X 10-7 T2

0) Calculate the reactor heating or cooling requirement in kJ/mo! feed
(ii) Why would the reactor be designed to yield such a low conven;ion of ethylene?
What processing steps would probably follow the reaction in a commercial
process?

8. (a) Ethyl alcohol can be bacterially oxidized to a~etic acid in the following two step
fermentation seqiJence: (17)

2C2HsOH + 0, -+ 2CHJCHO+ 2H:>9

2CHJCHO+02 -+2CHJCOOH

ConW P/4
 =4=
CHE201lCHE
Coutd ..• Q. No. 8(a)

If the a1cohol- containing feed stock is derived from malt solution, the resulting solution
is vinegar. An aqueous solution containing ethyl alcohol in water is fermented to
produce dilute acetic acid. The feed mixture (the ethanol solution) and air are led at a
temperature To. The product soiution contains ethanol, acetaldehyde (CH)GIO), acetic
acid and Waler. All liquid and gaseous effluents are at temperature T. Perform a degrees
of freedom analysis for the process and specify the design variables that must be known
to solve the problem completely.
(b) Methanol is added to a storage tank 'at a rate of 1200 kglh and is simultaneously

withdrawn at a rate mw (t) kglh that increases linearly with time. At t = 0 the tank

contains 750 kg of the iiquid and mw =750kglh. Five hours later mw equals 1000

kglh. Calculate an expression for mw (t) and incorporate it into a differential mass

balance equation for the system. Find the expression for mass of water in the tank at any
lime t. Calculate how long it will take for the mass of methanol in the tank to reach ilS
maximum vaIue z and calculate that valllC.When will the tank completely drain oul? (18)

1300

.. _.. ------ --- --.

"'"
ltOO
, " -----
~.Ie,.nce stales'
Water, liquid at 3Z'f
NH3' liqu'd al-~F
IliOO
900 _, _~ _

'"
'"

'"o
-lOO _L"l" d Pha:s~

-2"
0,0 0,1 0,2 0.3 0,4 05 0.6 0.7 o.e O.g 1,0
~ lrnass lra":lOn NH]I
_ Enthalpy-conl;enlration diagra!\1
for the 1lmmonia_water system at 1 arm. (From
G_G, Brown et aL, Unit Opl!fq/ions, 101950, Fig-
ure 551. Reprinted by permission of John Wilev
& Sons.l .
 L-Z/I'-lICHE Date: 13/12/2014
(' BANGLADESH UN1YERSITY OF ENGINEERING AND TECHNOLOGY, DHAKA
..G-- L-2IT-] B. Sc. Engineering Examinations 2013-2014

~ Sub: CHE 203 (Chemical Engineering Thermodynamics-I)

\lj Full Marks: 210 Time: 3 Hours

USE SEPARATE SCRIPTS FOR EACH SECTJON
The figures in the margin indicate full marks_
----_ _ ---_._----- -----------_._-----------_ _---- ---------

SECTJON-A
There are FOUR questions in this section. Answer any THREE.
Notations indicate their usual meanings.

I. (a) Outside temperature of a cold country is -Soc. For comfortable living the inside of a
-~=-- -- .
-
house is to be maintained at 27°C. One kilowatt electric power is available for room
heating. What is the heating potential of this electric power? (12)
(b) With neat sketches describe the working of an ideal vapor-compression refrigeration

cycle. (13)

(c) Discuss the differences between the ideal and the actual vapor-compression cycles. (10)

2. (a) Derive the Maxwell Relations. (9)

••
(b) Show that CP-C•• T[~PJ [av) .
oT"BT p
(16)

(c) Write a short note on Joule-Thomson co-efficient (include inversion temperature and

related terms in your answer). (10)

3. (a) Discuss the different ways of improving the efliciency of a simple steam power

plant. (15)
(b) After using all the ways of improving the efficiency of a simple steam power plant
(as discussed in part (a) of !his question), the efliciency.still remains much below 100%.

Discus:; the underlying factors responsible for this. (8)

(c) Describe the operillion of a dual-cycle power plant. Properly explain why the dual-

cycle efficiency is higher than the simple cycle ones. (12)

4. (a) Derive the expression lor thennal efficiency of air-standard diesel cycle. (20)

(b) Derive the expression for thermal efficiency of a simple gas-turbine cycle. (15)

Conld P/2
 =2=

CHE203/CHE

SECTION-B
There are FOUR questions in this section, Answer any THREE.
Property tables are provided,

5. (a) Write short notes on (3X4=12)

(i) control mass and control volume
(ii) extensive and intensive properties
(iii) zeroth law of thermodynamics
(b) Draw and explain P-V and P-T diagrams for a typical pure substance. (12)
(cl What do you nnderstand by the quality of a vapour-liquid mixture? (3)
(d) A 20.0-m] tank contains nitrogen at 2)uC and 600 kPa. Some nilrogcn is allowed to
escape '~I th~ pressure in the tank -;;;p;to 400 kPa. If the temperature at this
--
temperature at this point is 20oC~determine the amount of nitrogen that has escaped. (8)

6. (a) Derive the energy equation for a steady-now system. (15)

(b) An adiabatic air compressor is to be powered by a direct-coupled adiabatic stearn
u
turbine that is also driving a generator. Stearn enters Uteturbine at 1~Pa- and 500 C

-
98 kPa and 295 K at a rate of I0 kgls and exits at ,-
-
at a rate of25 kgls and exits at 10 kPa and a quality of 0.92. Air enters the compressor at
- I MPa and 620 K. Determine the net
power delivered to the genenllor by the turbine. [Property tables are provided] (20)

7. (a) Write down the "Kelvin-Planck" and "Clausius" statements of the second law of
thermodynamics. Show that both the statements are equivalent. (2+2+6=10)
(b) An inventor clailll.'lto have developed a resistance heater that supplies 1.2 kWh of
energy to a room for kWh of eleelricity it consumes, [s this a reasonable claim? (5)
(c) Define reversible and irreversible processes? What are the irreversibilities we
experience in an irreversible process? (4+6=10)
(d) An inventor claims to have developed a heat engine that receives 700 kJ of heat from
a source at 500 K and produces 300 kJ of net work while rejecting the waste heat to a
sink at 290 K. is this a reasonable claim'! (10)

8. (a) How can you save work by using multistage compression with Intcrcooling? Explain
graphically. (10)
(b) Draw and explain typical T-S and h-S diagram for a pore substance. (10)
(c) A 50-kg iron biock (ep = 0.45 kJlkg. 0c) and a 20-kg copper block (C~ ~ 0.386
kJlkg. UC), both initially at 80°C, are dropped Into a large lake at 15°C. Thermal
equilibrium Is established after a while as a result of heat transfer between the blocks
and the lake water. Determine the total entropy change for this process. (15)
/
.. ,. . .
"

.,~.•
" -." -
.
..., """
-,"
•
",,
m•• ted water 'Contmued!
, , ,
"m'lkil -
"kJlkiI "", "'" m'/kg "
'q kJl1'11 """ - ~,- • ~'"
.•. . "
,
~,':n -,
•
",m
,~
,00
p ~

O,0497B 2601.7
4.0Mr,

0,05461 2668,9 2881"

005881 2726,1 296Ll
«00.35'<:)

"~.
6.0696
62312

,~
6.3639~,
0,05842
0.04733
0,05138
p ~ '.5 MP, {Z57."OCI
.'599,7
26\U
2113,0
2815,6
2J98.0
2804.4
601911
614Z!l
6.za~.
,,0 'MP. !~"3 94'<:1
0,03945 2597.0 '2704 2 5.9731
0,0414. 2632.3 2889 5 0.0571
Q.[l45~5 2699.0 2925.76,2111
:KlB1.5 6,5153- 0.05197 2809.5 '3069.3 64516
0,066.7 2827,4 3093.3
6,nU 0,00477 291.l ,205.7 6.70ll 0.05784 2907.5 3196-7 6,6.88
.00 O,~,,.2920,8 ,~.5

"
~
O. 1'30110" ~- 69,861 lflD1076
0.08644 3100,3 ~446_0 7.0912 -'(1016,2 ~'"
3096,0
3324.. 6.BnO
3440.4 7.03".
O,0633211~~317_i:D'
006858, _ ,"3434.1 '6.
~
'00 0.11098 ,~,
0.09886 3279.4 3(;74.9 7,3700' ".08766
3\Kl6.3 ) 6214 009850
0.1001G
,~,
021&.4

3008.8
3670.9 7.3121
3903.3 7,G')
4"00
0,07870 3273.'1" %66.9 7.2605
O,0B8~l 34~7,7 39Q1}.37.5136
1.'9G2 00'l61G 36469 '137.7 7.7_
~ 012292 3650,6 4142.3 7 B623
Q.1l972 3843.3 ~361,1 B01l6 0,1016g 364J.6 ~3602 7.9619
'00 0,10'16 3844.6 ~3B3,9 60675
40U9 46/9$ 6/144 0.1\715 4042.6 46163 6,1648
'00' 0,14653 4045.1 46312 6,2698 013010
0.\2655 424~.3 4882 1 8,3566
UOO 0,15824 4261.4 4884A 6.46\2
o 16992 4463.5 5\432 R6430 01510) "'- 42504
4462.6
4883.2
5142,2 ,=,
84060
0.\3592 446l.6 5141,3 6,536a
,=
"00
O.J61~1 466O,9 5407.1 8 816~ 016140 4680,1 640G.5 8,761G 0.14527 4679.3 5405.7 $.7\24
,
,. 6,0 "'P, (275,S'l"CI P ~ 1 0 M~, Ic85 s3'C1
-
8,0 MP, (~90 Ql'el
27~8 7 5.7450
0.03145 2589,9 17$4.6 5,8'l{l2 0.027378 15810 27/2.6 5.8148 0,02352& 2570,5
",.
'00 0.00619 266$.4 28!!5.6 6,070J
0,04225 2/9J.4 3043.9 6,3l57
o ~2~492 20>.'1.5 28399
0.03;262 ,770.1 3016.9 6.2305
0.933/ 00242/9.5923
0,029975 27~8 3
~786.5 5.7937
,98S.1 6.1321
0,Ol995S 2S)9.5 31592 6.4502 0034344 2a64 6 3139.4 6.3658
'00 004742 2893.7 31JS.3 6,54)2 '1273,3 6.5519
004418/29/90 3288.3 6.6303 0,0).8194 2961,8

=
';0 0,00211 2gS9.Q no2.9 67119
,= 3399.5 6.7266
,~ 0,0(;667 3OB).1 3423,1 68!!26
. 0,06102 3\1'.2 35413 7,0,08
0.04610/ l070 3411.~
0.051%6 3167.9 35:316 6,9007
0,0~1161 3065,4
0.045172 3160.6 3521.8 6,8aoo

=, ,-,
360(1.6 7,0010 0.046463 32S4.7 3642,47,0221
~ 0,0.,27, 32.7 .• 3658.6 7,]693 0.05~5 3261.0 3882,27,18 ••
• '00 0,07355 :3-453.0 3894,3 7.4207 0,062650 3448.3
>'llOO'" 0,08165.+3043.2 '41H3 l, 7,658:2 a 069ll'i6 3639.~ 4128,5 7,SOU' ,=, 0.05<829 3"3.6
o 061O11 3635.7
0.067002 3932.7
01,3$ 7,,185
4369 3' 1 7312
~ 008964 3838.8 4376,6 7.8751 "0161;0 3935.7 ~3no .
,~ 009756 40401 462,' 8.0766 0083571 ~0".5
noo 0,10543 ~247,1 4879,7 8.2709 0,090341 4245,0 ,877.4 6,1982
4622,5 $ DO'5 0,073079'4035.0,
0079025 4242.a
46196 7'>410'
4875.06,ll50
,=
,=
0.11326 ~459 8 5139"
54(>\,1
8.4534 00970754457.9
8.62/3 o 1037S1 46/61
5137,4 ~ JalO
5402.6 S.5551
0,0a4934 4455,1
0,0908174674,
5135.5 8,3181
5-401.0 8.4925
0.1210/ 4677 7
I' egO MP.ll03 30"-') p_mOMI'o13l1O'fGI , 12.5 MP, (327.81"CI
5.615g 0013496250,,6 2674.3 5,~53a
~. 0.0204l19265115 2742.9 5.Glgl 0,01802A 25451 272;.'

,.
'"
0.023.~ 2647.6
002581627250
2B57.1
'2957.3
5.873S
6.0060
62$16
O,0]~817 2611.6
o 022440 ~699 c
O.DlG~36~6lU
2810.3
2924,0
30915
,.W
5./596

6,2\'1
0,016136 2';2~,9
D020(-.10 2]89"
~8.6 6 5.7130
3040,0 5,04J'
,~
'00 0,029900 2649,~
0,OJJ52429,6.3
3118.8
3258,0
33S14
6~872
6,660,
o 0.~782 2944.5
o.os.all 3047.0
""4
3375,]
6,4/1~
65995
D.023019 29H.7
0,025&30 3023,2
3201.5 6,2"9
33H 6 6.4651
~ 00)679, 3056.3
0.028033 31~6.1 3476,56,6,17
0.039886315,,0 3;120 c.a164 0,03(;655 3145.4 35020 6.758'
'W
,. 3634,1 6960, 0,038'1JS 3242,0 )625.8 6.004; 0.Cl.JO'1063~25.8 3604 5 6.182A
'00 0,042S61324a,4
7.0954 0,041018 3338,0 3J4A.l 7 0408 0032491 l324.1 37'10.2 6,9227
0.0457553,43,4 3755,2
7.n29 0,04'1597 34340 3870.0 71693 0,034612 34Z2,0 385( 6 7,0540
'00 0.048'500 3438,6 387£')
41192 7.4"06 Q,04B6~9 3628,2 4114.; 7.4065 0,008724 3618,a 4102A 72967
~ 0.054132 3632,0
436l.9 7,519,
,~
~
"00
o OS95623829 6
0.0649194032.4
0.0702244240.7
4365.7
.616.1
4812.7
7.66O~
7.11855
6,07~1
005l5473826,5
0.0583~1 4O~.~
0.063183 ~nB.6
4362.0
4613,6
4870,'1
7.6290
1.a349
B0289
0~2720 38189
0,046641 4023,5
0,060;10 4233,1
4606., 7.7269
48(0) " 7 9220
51336 8 26~5 0.067936 445~,4 5131,) 8,21~6 0.054342 •• ~1.7 5127,06,1065
1200 0,075<924'1>4.2
,,99.5 S4l11 0.0/2667 4671.0 ;3980 a3874 0.068147 4667.> 5394,1 8,26]9
1300 0.08073-34612.9
 Il. "l~)
'"
"
/
Ide"'.g..
,, "
'"
'W
""
199.97
209.97
,CO 219.97
230,02
~pertl.,of .ir

" ""
0.3363
0,3987
0,4690
0,5477
"
142.56
149.69
156.82
164,00
",
1701.0 1.29559
1512.0 1.34444
13460 1.39105
,1205,0 1.43557
<
1<JII<~ • K ,, "
,~
;0'
;00
,W
kJlki
586.04
596.52
607.02
617.53
"
14,38
15,31
16.28
17.30
- -,
"
419.55
427.15
434.76
442.42
115.7
llO,S
105.8
101.2
",
<
2,37348
2.39140
2.40902
2.42644
'"
'" 250 05
240,02 0,6355 171.13 1084,0 1.47824 ,CO 628.07 18.36
19.84
450.09
457.78
96.92
92,84
2.44356
2.46048

'"'" 260,09
0.732'1
0.8405
178.28
185.45
979.0 1.51917

~.,
887.8 1.55848 ""'" 638.63
649,22
65984
20.64
21.86
46550 88,99
473,25 86.34
2.47716
2,49364
,~
'" 270,11
280,13
0.9590
1.0889
192.60
199,76
1.59634
738.0 1.63279
';0
'"
67047
&81.14
23,13
24.46
481.01
486.81
81.89
78,61
2.50985
2,52589

'" 285.14
290.16
1.1584
1.2311
203.33
206.91
706.1 1.66055
676.1 1.66802 ''"
~ 691.82 26.85 496.62 75,50 254176
'"
'"'" 296.17 1.3068 210.49 647,9 1,68515
'" 702.52
713.27
27.29
28,80
50445
512,33
72.56
69.76
2,55731
2.57277

'"
29818
300,19
1 3643
1.3860
1.4686
212.64
214.07
217.67
631 9 1.69528
621,2 1.70203
596,0 1.71865
'"
no
no
724,04
73482
30,38
32,02
52023
528 14
67.07
64.53
2.58810
2.60319
'0; 305.22

Spoclflc !'alUm<!, Int"".1 "'''411', f:mll./py, f:olropy.

s.!. ~"
•• ••• "" ,. ••
kjlkg
Sat, s.t.
kJiIIol • K

.~,
S,t.
"' "~
'.
E"p , "po,. liqUid, E•• ~"
P••••.. wnp .• liq"id, "PO'. I,ouid. E"p" liQ"id.

"" ",
r~1"C ", ". ".
2355.•
",
2384,5
"
29,OJ
hll

24a-(,O
",
25u'7
'"
01059 8,8690 8,9749
"-~
",.,
6.97 O.OGlOOO1.9.19 29,.3-02
5~,6B6 2338.1 2,928 54,6<18 24'0,1 2524.1 0.195G 8,6314 88270
13,02 o 0010m 87.964
06._ 13431 l320., 2391l,~ 73.'33 2459.5 2';.12.9 0,2606 8,%21 81227
"" 2~OB
17,50 0001001
2l.(l8 0.001002 04,"'2
0001003 46,684
88.022
100.98
23154
2306,9
2400,8 88424
2~01 9 100,98
2451.0
24-43.9 ,~, .m'
2539.4 0,3118
0.3543
8.&421
8,2222 85J05
"
'.' 28.96 0.001004
0.001005
34191
28,la5
121.3g
137.75
2293,1
2282.1
2414.5
2419.a
121.39
131.75
2~32.3
24230
2553.1
2560.7
Q~224
0,416'
8.0510
1.9176-
84734
8.3938
CO 32.87
19233 I£a 7~ 2261.J 24298 168.75 2405,3 2574.0 05763 1.67JB 6.2501
40.29 oOOl00a

"""
1~,670 191.79 2437.2 191.81 2392,1 25839 0.6492 7.4g96 8.1488
4Ml 0.001010 "'45-4
10.020 225,93 2222.1 244a,0 225,94 237?.3 2598,3 0.75~9 7.2521 80071
53.97 0.001014
W ".~ 0.001017 7.6431 251.40 22046 2456,0 25142 23,7.5 2508,9 O.I3JZO 7 0152 7,9071

" ,,~ 6.2034 27193 2190.4 271.96 2~~5.5 2617.5 0.8932 69370 7,830l
64,96 0001020 M'
5.2287 289,Z4 2178, 2461,7 28927 2,35.3 2624,6 0,!I441 68234 7.7675
0,001022
"•• 75 SO 0001026 3,9933 31158 215B8 2476.3 317,62 2318.4 2636.1 10261
1.0(1)2
6.6430
65Qlg
7.66g1
7.5931
• 8132 0,001030 .1,2403 340,49 21411 24B12 3~O.54 1304.1 2645.2
 L-Z!T-l/CIIE Date: 10/0l/2015
BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY, DHAKA
L-2iT-1 B. Sc. Engineering Examinations 2013-2014 \<.~
Sub: CHEM 235 (Physical Chemistry II) t';t~t-~r"
,(,
Full Marks: 210 Time: 3 Hours ,~.
USE SEPARATE SCRIPTS FOR EACH SECTION ~
The figures in the margin indicate full marks.

SECfION-A
There are FOUR question:; in thi:; section. Answer any THREE.

1, (a) What are reversible and Irreversible cells1 Explain ,,vith suitable examples. (6)
,
(b) Derive an,expression for the variation of emf of a cell with temperature,
~,' (14)
(c) Shdw the'half cell reactions and overall reactions for the fol1{ming cells: (6)
(i) Pb, PbCl:!(s): KC1(aq) I AgC1(:;), Ag
(ii) Pt I c~t,
Cu2+ II Cu+ I Cu
(d) Formulate a cell for which the fullowing reaction Could occur: (9)

Fe1+ +.!- Br1 "" f"cJ+ + Br-

2
Dcterminc EO, I'iG~ and K lor the reaction at 25"C (Given: E;'IF"',F," "" ~O.77 volt and

E;"B,,(11B; = 1,065 VOll).

2, (a) \Vhat do you mean by the term "concentration ccll'''l Explain with a suitable
example. .(8)
(b) Discuss how you ean determine the activity coefficient of an electrolyte from emf
measurement ofa cell. (17)
(c) Calculate the mean activity coefficient of 0.1 m hydrocWoric acid at 25°C. Given
thattheemfofthecell. (10)
H1{l atm) I HCI (aq) I AgCl (s) I Ag
is 0.3524 volt at 25"C and the standard electrode potential of Ag-AgCl is 0.2224 volt at
25"C.

3. (a) State and explain the Ostwald dilution law. How can you determine the value8 "fX
and Ac for weak electrolytes with the help uf thi~ law. (The symbols hear u~ual
meaning.) (16)
(b) What is mC<lntby salting-in effect? Show lhal the solubility of a sparingly soluble
salt mcmases with lh~ in{,:reasing concentration of an electrolyte having no common ion. (12)
l
(e) The solubIlity of silver iodate in pure water at 25"C is 1.77 x 10--.4mol L- . Calculate
the solubility in the presence of 0.3252 x 10-1 mol L-1 of potassium nitrate. (7)

4. (a) State the phase rule, Explain the terms pre"~nl in it and derive it. (12)
(b) Draw the phase diagram of a ~ystem of water and a salt which gives two or more •
hydrates. Briefly discuss the Important inlimnatiun that can be obtained from the
diagram. (15)
(c) Define the following tenns: (i) Tripplc point (ii) Eutectic point, (iii) Congruent
melting point and (iv) Peritectic change. (8)
Contd P/2
 =2=
CHEM 235/CHE

SECTJON-B
There are "'OUR questions in this ~eetlOn,Answer any TUREK

5. (a) 'What is a zero order reaction? Show that for a zero order reaction the conecntration
varies linearly with time. (2+6=8)
(b) For the following reaction the forward reaction is third order and the reverse reaction
is second order. Derive the fate expression ilIld show how the rate e~pression ean he
used to determine the value (lfrate constants k2 and k)
')
2:"0+02 ( ) 2NOl
"
(c) M"z, In produ~ed in the reaction of potassium pennanganate with oxalic acid In

presence of sulphuric acid acts as a catalyst. Show the mechanism of the catalysIs. (7)
(d) Show the steps in the hcterogeneous eatalysi~ ;;~cording to adsorptIOn theory of
catalysis. (8)

(a) 'What are the ongms of adsorpllon spectra of inorganic compounds during the
analysis m lTV-Visible spectrophotometer. (12)
(b) What is an auxochrome? 'What are the main functions of auxochrome? (3+6=9)
(c) What is the rigid rotor model of a yibrating diatomic molOl.'ule?What happen~ wh,,'U
the mokcnk do not obey the ideal rigid rotor model? (8+6=14)

7. (a) What i, multilayer adsorption? Why solid surface follow multilayer adsorption rather
than monolayer? (3+5=8)
(b) Derive an expression WhlCh tollow Langmuir "dsurption isothenn for" dynamic
adsorptioll-desorptioll process. How the equation can be applied for the detelmination of
surfaec area? (10)
(c) Write the mathematical cxpre>sion of phase rule for condensed system with brief
justificaTIon. (4)
(d) Discuss the thermal analysis method for the detennination of equilihrium conditions
between solid ,llld liquid phases with suitable diagram" (13)

II. (a) Di~cu.<,sthe chronological development of the theories of cJectrolytl~ conduction.

Whieh jaw supports the modern theory of electrolytic conduction'! Briefly dcs"Tibe it. (14)
(b) Desenbc a method hy which you can determme thc conductance of an ckdrol)tie
s"olution.What \8 cell constant'! (8+2=10)
(c) Describe in details the applieatlOn~ 01' conductilllee measurement 01" electrolytic
solution. (11)
L-2ff-liCHE Date: 15/01/2015
BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY, DHAKA
L-2iT-I B. Sc. Engineering Examinations 2013-2014

Sub: EEE 267 (Electrical and EI""tronicTcchnology)

Full Marh: 210 Timc : 3 Hours

USE SEPARATE SCRIPTS FOR EACH SECTION

The figures in the margin indicate full marks_

SECflON-A
There are FOUR questions in this section, Answer allY THREE.

I. (a) Evaluate the voltage VA and current IA in th~ circuit shown in Fig. l(a) (15)

,
~.

\O\UL f-)

. ~
:i.~~;1
~ ~ C~~

~
, ...-- -'- -
.~

_ - -~

(b) Determinc the voltage gain and I/O impedance of the circuit shown in Fig, 1(h), (20)

Contd. _.. P/2

 "'2'"

EEE 267/CHE

2. (a) De.'>lgnan analog computer to solve the follO\\iing differential equation, (20)
d2v o dv
----r-+3-+vo"'O, t>O
dt dl
Suhjectto vo(O)=4 and v;,(O)•• O.
(h) The triangular wave limn of fig. 2(a) is applied to the i')put of the op-Amp
differentiator m Fig. 2(b). Plot the output. (15)

O.OI.J..lF lOOK,,)).

3, (a) Desib'll a diode circuit within the "Black Box" in Fig. 3(a). (17)

t +S
Bla~~ . /' '1.~
V,, " vOv-t '
BoX

(b) Design a diode drcuit to implement the followmg LlO relation: (18)

4. (a) Define "Transducer"- Discuss the working principle of capacitive transducer. (HI)
(b) Define "Piezoc1ectricity", Show how it can be employed to measure temperature and
force. (15)
(c) Draw V"u' for the circuit m Fig 4(c). (10)

Contd . " ..... , Pl3

 =3=

EEE 267/CHE

SECTION -8
There are FOUR questions in this section. Answer any THREK

5. (a)A three phase, balanced Y-eonneeted motor takes 10 kVA at 0.7 power-factor
lagging from a source of220 voils. It is paraileled with a balanced three phase delta load
having impedance of (15-j 10)0 in each phase. Find (i) the totai kVA (ii) line current

(iii) power-factor of the combination. (20)

(b) Prove that, single pha:.e system uses 33 percent more material than three phase
system to uehver the same amount of power with fixed line loss for the same line

voltage. (15)

6. (a) What is annature reactiun? How docs it affect the operation of DC machines?

Explain with apprupnate diagrams. (12)

(b) What are compensating windings? Briefly explain how they can solve the probkm
of commutation in DC machines. (11)
(l:)A 200-kVA, 480-V, 50 Hz, Y-eonnected synchronous generator with rated field

current of 5 A wa:; tested. The following data were taken: (12)

(i) Open circuit terminal voltage, VT.OC= 540 V at If ~ 5 A.
(11) Short circuit current, 11.,sc = 300 A at If = 5 A.
(iii) When a DC voltage of 10 V was applied to two of the terminals, a ~urrenl of
20 A was measured.
Find the values of armature resIstance and synchronou.' readance.

7. (a) 'Open circuit test minimizes copper loss' - explain. (5)

(b) Draw phasor diagrams of a transformer operating at different PU"'ef factor uf loau.
Huw docs the power factor ofload affect the voltage regulation of a transformer? (10)
(c) A 75-kVA, 4600-230 V, 60 Hz single phase transformer has heen tested to determll1e
its equivaknt circuit. Test results are: (2U)
Open Circuit Test Short Circuit Test
Voc=230V Vsc = 160.8 V
loc=13.04A he = 16.3 A
Poc = 521 Wall Psc- = 1200 Watt

(i) Find the impedance of the approximate equivalent circuit referred to the high
side, and sketch the circuit.
(il) Find the voltage regulation of the transfonner at rated conditions at 0.75 power
faclor lagging.
(iii) Fmd tlle efficiency of the transfonner at rated eonditlOns at 0.75 power factor
lagging.
Contd P/4
 =4=

EEE 267/CHE

~. (a) D~'Tivethe torque"~peed characteristic ofa series DC motor. (12)

(b) Briefly expbin how speed of a shunt DC motor can be varied by changing the

armature voltage. (6)

(c) A IOO-hp, 250 V, 1200 rpm shunt DC motor with compensating windings ha~ an
armature R",istance of 0.03 0 and field resistance of 41.67 n. The motor IS assumed to
be driving a load with a line current of 126 A and an initial speed of 1103 rpm. Assume
that change in field resistance does not affect the armature current. Thc magnetizing

curve for this motor, taken at a speed of 1200 rpm is given in tabular form below: (17)

EA, V 83 125 180 220 250 270 280 284

If, A 1 2 3 4 5 6 7 8

(i) Find the armature current and intemal genL'J"atcdvoltage of the motor.
(ii) What will be the value of motor speed if the field resistance IS mereased to
500~
(iii) Determine the value of field resistance for the motor to nm at its rated speed.
 L-Zff.lICHE Date: 07/1212014
BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY, DHAKA
L-2fT-I B. Sc. Engineering Examinations 2013-2014

Sub: MATH 221 (Vector Analysis, Matrices and Laplace Transfonns)

Full Marks: 280 Time: 3 Hours
USE SEPARATE SCRIPTS FOR EACH SECTION

The figures in the margin indicate full marks.

-- -------- ----_. __ ..• _--
SECTlON-A
There are FOUR questions in this section. Answer any THREE.

1. (a) The line that joins one vertex of a parallelogram to the middle of an opposite side
trisects the diagonal- Prove vectorially. (20)
(b) A force of 6 units acts through the point P(3, -2, 5) in the. direction of the vector
(7,6, -I). Find its moment about the point A(I, :...], 1)~dthe ~o~ent about axes
~
through that point parallel to the coordinate axes. (16Y,)

(c) Give the geometrical interpretation of the scalar triple product. (10)

2. (a) State and prove Frenet-Serret fonnuiae.

(b) If P = Acoskt + Bsinkt, where A and B are constant vectors and k, a constant scalar,

show that !!....(p, dPJ = O. (10)

dt dt

(c) Find V" (r"r) where r is the position vector. (15)

3. (a) Find the angle ofintersection at the point (-3,0,-5) of the spheres
x2 + y" + z" + 6x-5y+ 2z + 27=0 and x2 + y' +Z2 -29=0. (lS)

(b) Show that the gradient of a scalar function/is a vector along the normal to the level

surface whose magnitude is the greatest rate of change off (16Y,)

(c) Find curl ofF where F = (x2

- / + 2xz) i + «(xz-xy+ yz) j + (Z2 + x2) k. Also
show that the veclors given by curl F at the points P(I, 2, -3) and QI(2, 3, 12) are
orthogonal. (IS)

4. (a) State and verify Green's theorem in the plane for f(2x- i).u -xy<tY where C is the
c

boundary of the region enclosed by x2 '" / =I and x2 + y2 = 4. (26jD

(b) Evaluate JJJ(2x+ y)dV where V is the closed region bounded by the cylinder
,
z=4_x2 and the planes x=O,y=0,y=2 and z=O. (20)
Contd PI2
-
 =2=

MATH 2211CHE

SECTION-D
There arc FOUR questions in this section. Answer any THREE.

5. (a) Reduce A=[~ ~~ ~ ~] (20)

2 3 3 2

to the normal fonn B and compute the matrices P and Q such the PAQ = e, where A

and e are equivalent matrices.

(b)Give A",
1 2 3]
0 3 2 , (16)
[ 154

find K1 by algebraic method.

(c) Find the matrix A satisfYing the following matrix equation

[23 21]A[-3 5 -3
2].[-2 4].3-)
(lOX)

6. (a) For what values on and fl, the following system of equations (15)
2x+3y+5z",9
7x+3y-2z",g
2x+3y+k=p

will have (i) unique solution (ii) no solution.

(b) Show that the quadratic form q = x? + 5xj + 6x; + 4x[x2 -8X2X) -6X3X1 is indefinite

and find two sets of values of Xl> X2, x) for which the form assUmes positive and

negative values. (15)

(cl State and prove Cayley's Hamilton theorem and also verify the above theorem for the

matrix A=[~ ~] and hence find A-I. (16X)

7. (a) Evaluate (8+8+8=24)

(1) L\[fW,j
(iil LV~))
(iii) L{Jo(at)}
Conld .......... PI3
 ~3=

MATH 2211CHE
Contd •••Q. NO.7

(b) Using laplace transformation, show that Jo i(11+/

" -"
)dt = lre'erJi:(JI). (16,%)

(OIFi'dC'(( sl +2s+S
1 ri. (6)

8.
,.
(a) Using laplace transform, evaluate - Jcos(tcosO)dB. (16)
'0
(b) Solve (using laplace transform) (20.% )

1"(')- Y(')- y'V) 4('-,-')

0

l"v)+ y(')o ,(, +3'-")

,(o)o'{OH
(c) Solve: ty"(t)+ y'(t)+ 4ty(I)= 0; y(O)= 3, y'(O)= 0 using laplace transformation. (10)