Republic of the Philippines

AUXESIS REVIEW CENTER

Manila

CHEMICAL ENGINEERING PREBOARD EXAMINATION

DAY 2
8:00 am – 5:00 pm search
own knowledge

CHEMICAL ENGINEERING PRINCIPLES SET A

INSTRUCTIONS: Select the correct answer for each of the following

questions. Mark only one answer for each item by shading the box
corresponding to the letter of your choice on the answer sheet
provided. STRICTLY NO ERASURE ALLOWED.

MULTIPLE CHOICE

1. A unit operation is exemplified by the process of

A. Desorption C. Combustion
B. Reduction D. Nitration

2. Zirconia probe is used for the continuous measurement of

__________ flue gases going out of the furnace.
A. carbon dioxide in C. temperature of
B. carbon monoxide in D. oxygen in

3. Typical specifications for design stipulate the gain margin

and phase margin to be respectively
A. < 1.7 and > 30° C. < 1.7 and < 30°
B. > 1.7 and > 30° D. > 1.7 and < 30°

4. Higher efficiency in the combustion of solid fuel cannot be

achieved by
A. proper fuel preparation.
B. keeping the flue gas exhaust temperature very high.
C. adopting efficient-fuel firing technique & equipment.
D. supplying correct quantity of combustion air.

5. In flue gas analysis by Orsat's apparatus, carbon monoxide is

absorbed by
A. alkaline pyrogallol solution
B. cuprous chloride
C. potassium hydroxide
D. none of these

6. The minimum baffle height should be

A. equal to the impeller diameter.
B. twice the impeller diameter.
C. twice the tank diameter.
D. 3/4 of the tank height.

7. Which of the following temperature measuring instruments need

not touch the object whose temperature is being measured?
A. Radiation/infrared pyrometer
B. Filled system thermometer
C. Mercury in glass thermometer
D. Thermo electric pyrometer
8. The normal range of velocity of water in pipes is __________
m/sec.
A. 10-50 C. 15-30
B. 0.1-0.5 D. 1-2

9. Removable connection of tubes to tube sheet is called

A. socket C. saddle
B. nipple D. ferrule

10.What is the slope of the operating line in the rectifying

section of a distillation column?
A. 0 C. <1
B. > 1 D. ∞

11.For a given design of bubble cap, the number of bubble caps

to be used per tray is set by the
A. allowable gas velocity through the slots.
B. plate spacing.
C. diameter of the column.
D. any of these

12.The shell side pressure drop in a shell and tube heat

exchanger is maximum for __________ baffle.
A. orifice C. segmental
B. disk and ring D. independent of the type of

13.The function of manholes provided in the shell of a

distillation column is to
A. keep a check on the liquid gradient over the plate by
direct visual observation.
B. give access to the individual trays for cleaning,
maintenance and installation.
C. guard against foaming & entrainment by dumping antifoaming
agent through it.
D. Any of these

14.__________ closure is the weakest enclosure for cylindrical

vessels.
A. Elliptical C. Conical or flat plate
B. Hemispherical D. Torispherical

15.Log mean temperature difference in case of multi-pass shell

and tube heat exchanger is always
A. less than arithmetic mean value.
B. more than arithmetic mean value.
C. more than geometric mean value.
D. any of these

16.Which of the following reactions occurring during coal

gasification is called the Neumann reversal reaction?
A. CO + H2O = CO2 + H2 C. C + H2O = CO + H2
B. 2CO = C + CO2 D. C + 2H2O = CO2 + 2H2

17.The drug used in contraceptives is It has a role as a flavouring agent, a

A. sulphadizene prevents infection in any
part of the body
C. methyl salicylate metabolite and an insect attractant.

B. mestranol D. pencillin medication used to manage and treat a wide range of

infections

18.Maximum work that could be secured by expanding the gas over

a given pressure range is the __________ work.
A. adiabatic C. isothermal
B. isentropic D. isochoric
19.High __________ is an undesirable property for a good
refrigerant.
A. specific heat
B. latent heat of vaporization
C. viscosity
D. specific vapor volume

20.Fundamental principle of refrigeration is based on the

__________ law of thermodynamics.
A. zeroth C. second
B. first D. third

21.Degrees of freedom at triple point will be

A. 1 C. 2
B. 3 D. 0

22.In distillation, overhead product contains

A. any number of components
B. only one component
C. only saturated liquid
D. two components

23.The ratio of volumes of the mixed reactor to the plug flow

reactor (for identical feed composition, flow rate,
conversion, and for all positive reaction orders) is always
A. < 1
B. equal to the order of reaction
C. 1
D. > 1

24.Pick out the wrong statement.

A. Due to uneven supply and improper distribution of
liquid, problem of channeling, loading and flooding is
generally encountered in packed towers.
B. Diameter of randomly packed tower is normally more
than 1.2 meters.
C. Packed towers are preferred over plate towers for
handling corrosive and foamy liquids.
D. Packed towers are preferred for vacuum operation,
because the pressure drop through the packing is less and
they (packings) also lessen the possibility of tower wall
collapse.

25.In turbulent flow, the

A. fluid particles move in an orderly manner.
B. momentum transfer is on molecular scale only.
C. shear stress is caused more effectively by cohesion than
momentum transfer.
D. shear stresses are generally larger than in a similar
laminar flow.

26.__________ flow means the flow of incompressible fluid with

no shear.
A. potential C. boundary layer
B. streamline D. creep

27.A negative gain margin expressed in decibels means a/an

__________ system.
A. stable C. critically damped
B. unstable D. none of these
28.Power number is the ratio of
A. inertial stress to drag stress.
B. inertial stress to gravitational stress.
C. gravitational stress to drag stress.
D. drag stress to inertial stress.

29.Response of a system to a sinusoidal input is called

__________ response.
A. impulse C. frequency
B. unit step D. none of these

30.Which of the following is used to set the diameter of the

distillation column?
A. Number of theoretical plates.
B. Static submergence.
C. Allowable vapor velocity.
D. Length of straight rectangular weir on cross-flow tray.

31.Pick out the first order system from among the following.
A. Damped vibrator.
B. Interacting system of two tanks in series.
C. Mercury in glass thermometer kept in boiling water.
D. Non-interacting system of two tanks in series.

32.A The function of a transducer is to

A. convert the primary signal into a more useful quantity,
usually an electric impulse.
B. modify the input signal.
C. amplify the input signal.
D. codify/decodify the input signal.

33.Which of the following thermocouples will give the highest

output for the same value of hot and cold junction
temperature?
A. Platinum-platinum + rhodium.
B. Iron-constantan.
C. Chromel-constantan.
D. All will give the same output.

34.Select the correct statement from the following:

A. The frequency response of a pure capacity process is
unbounded.
B. The phase lag of a pure time delay system decreases with
increasing frequency.
C. The amplitude ratio of a pure capacity process is inversely
proportional to frequency.
D. The amplitude ratio of a pure time delay system increases
with frequency.

35.Bakelite is
A. same as poly tetrafluoroethylene (PTFE).
B. an inorganic polymer.
C. same as thermosetting phenol-formaldehyde.
D. not a polymer.

36.__________ paper is used in the manufacture of newsprint

paper.
A. Groundwood C. Tissue
B. Board D. Wrapping
37.Glycerine is a by-product of the __________ industry.
A. oil hydrogenation C. paint
B. soap D. detergent

38.Response of a linear control system for a change in set point

is called
A. servo problem C. regulator problem
B. transient response D. frequency response

39.Hot wire anemometer is used for the measurement of gas velocity

A. very high temperature.

B. flow rates of granular solids.
C. thermal conductivity of gases.
D. flow rates of fluids.

40.Flooding in a vapor-liquid contacting equipment occurs in a

tray, when the pressure drop through a tray is __________ the
liquid head available in the downcomer.
A. less than C. very much less
B. same as D. more than

41.Estimate the diffusivity of acetone in water at 30oC. The

molar volume of acetone at its normal boiling point is 7.4 x
10-5 m3/mol.
A. 1.19 x 10-5 cm2/s C. 1.97 x 10-5 cm2/s
B. 1.33 x 10-5 cm2/s D. 1.68 x 10-5 cm2/s
wilke and chang 54.08 m^2/s

42.A fuel has the following constituents: Carbon 85%, hydrogen

13%, Oxygen 2%, When burning this fuel in a boiler furnace
the air supply is 50% in excess of the theoretical minimum
required for complete combustion, the inlet temperature of
the air being 31°C and funnel temperature is 280°C. Compute
its calorific value.
A. 47.2 MJ/kg C. 35.9 MJ/kg
B. 21.3 MJ/kg D. 12.5 MJ/kg

43.A liquid mixture containing 65 mol % methanol (CH3OH) and 35

mol % water is fed to a distillation unit composed of two
columns. The bottoms product of the 1st column (B1) contains
31.7% methanol while that of the 2nd column (B2) contains pure
water. The overhead product of the 1st column (D1) is fed into
the 2nd column. The final overhead product (D2) contains 94.5
mol % methanol which makes up 80% of the methanol in the feed.
Determine the mole fraction of methanol in D1.
A. 0.76 C. 0.88
B. 0.95 D. 0.60

44.Drying of a sample from 20% moisture to 15% moisture takes 2

hours. If the critical moisture content is 16%, and the
equilibrium moisture content is 4%, how long will it take to
dry the sample to a free moisture content of 5%?
A. 5.8 hrs C. 6.6 hrs
B. 7.1 hrs D. 4.9 hrs

45.Oxygen is diffusing through carbon monoxide under steady-

state conditions, with carbon monoxide non-diffusing. The
total pressure is 1 atm and the temperature is 25oC. The
partial pressure of oxygen at two planes 2 mm apart are 0.128
atm and 0.0642 atm, respectively. Calculate the rate of
diffusion of oxygen in kgmol/m2-h. Do2co = 1.87x10^-5
A. 6.87 x 10-5 C. 2.91 x 10-5
B. 3.41 x 10-5 D. 4.25 x 10-5
46. 500 kg/hr of milk containing 8.5% solids is fed to a double-
effect forward feed evaporator to produce a product
containing 40% solids. The evaporation from the second effect
is 2/3 of that from the first effect. What is the evaporation
from the second effect?
A. 169 kg/hr C. 158 kg/hr
B. 122 kg/hr D. 140 kg/hr

47.An unlagged horizontal steam pipe with an outside diameter of

30 mm at 380 K is exposed to air at 298 K. The emissivity of
the pipe is 0.9. Assume ℎ𝑐 = 1.18(∆𝑇/𝑑)0.25(W/m-K). What is the
heat loss by radiation and convection?
A. 65.3 W/m C. 127.5 W/m
B. 135.8 W/m D. 115.2 W/m

48.A plant produces phenol. The variable cost I pesos per tonne
of phenol is related to the plant capacity P (in tons/d) as
45000 + 5P. The fixed charges are P100000 per day. The selling
price of phenol is P50000 per ton. The optimal plant capacity
(in tons/day) for minimum cost per ton of phenol, is
A. 101 C. 283
B. 141 D. 422

49.The solubility of NaNO3 at 40oC and 10oC are 51.4% by weight

and 44.5% by weight, respectively. How many grams of NaNO3
may be crystallized from a 10 kg solution initially saturated
at 40oC if the temperature of the solution is lowered to 10oC?
A. 1243 C. 3897
B. 2550 D. 4089

50.A furnace has an area of 1000 ft2 exposed to the surrounding.

The furnace is made of six-inch thick insulating bricks with
a thermal conductivity of 0.15 Btu/hr-ft-oF. Th change in
temperature across the brick is 150oF. How much fuel is
required in lb/day to heat the furnace if the fuel has a
heating value of 15,000 Btu/lb?
A. 342 C. 72
B. 26 D. 610

51.An ideal gas Cp = (7/2)R and Cv = (5/2)R, undergoes a cycle

consisting of the following mechanically reversible steps:
An adiabatic compression P1, V1, T1 to P2, V2, T2.
An isobaric expansion from P2, V2, T2 to P3 = P2, V3, T3.
An adiabatic expansion from P3, V3, T3 to P4, V4, T4.
A constant-volume process from P4, V4, T4 to P1, V1 = V4, T1.
Determine its thermal efficiency if T1 = 2000C, T2 = 10000C,
and T3 = 17000C.
A. 63% C. 59%
B. 78% D. 42%

52.A circular tube of outer diameter 5 cm and inner diameter 4

cm is used to convey hot fluid. The inner surface of the wall
of the tube is at a temperature of 80°C while the outer
surface of the wall of the tube is at 25°C. What is the rate
of heat transport across the tube wall per meter length of
the tube at steady-state, if the thermal conductivity of the
tube wall is 10 W/m-K?
A. 27,646 W/m C. 17,279 W/m
B. 15,487 W/m D. 13,823 W/m
53.Acetone is to be removed from air in an isothermal dilute
absorber using pure water as solvent. The incoming air
contains 5 mole% of acetone (yin = 0.05). The design equation
to be used for obtaining the number of trays (N) of the
absorber is, N+2 = 6 log (yin/yout).For 98% recovery of acetone,
the number of trays required is/are
A. 1 C. 10
B. 8 D. 9

54.Two liquids P and Q having same viscosity are flowing through

a double pipe heat exchanger as shown in the schematic below.
Densities of P and Q are 1000 kg/m3 and 800 kg/m3,
respectively. The average velocities of the liquids P and Q
are 1m/s and 2.5 m/s, respectively. The inner diameter of the
pipes are 0.31 m and 0.1 m. Both pipes are 5 mm thick. What
is the ratio of the Reynolds numbers ReP to ReQ?
A. 1 C. 2.5
B. 4 D. 1.5

55.A kilogram of saturated steam at 10 MPa expands in a

throttling process to 20 kPa where its temperature is 100OC.
How much heat is needed to turn this saturated steam at
constant pressure into a superheated vapor with 600OC
temperature?
A. 889 kJ C. 712 kJ
B. 605 kJ D. 936 kJ

56.The feed plate of a continuous fractionating column handling

a binary system is the 5th plate from the top. A total
condenser setup collects a distillate with 90 mole% more
volatile component (MVC). The vapor streams entering and
leaving the 3rd plate from the top has 60 mole% MVC and 75
mole% MVC respectively. Assume constant molal overflow for
all plates and a constant relative volatility of 4.0. What
molar ratio of the reflux rate to the distillate rate is
maintained in the column at steady state?
A. 2.50 C. 3.00
B. 1.75 D. 3.50

57.It takes 6 hours to dry a wet solid from 50% moisture content
to the critical moisture content of 15%. How much longer it
will take to dry the solid to 10% moisture content, under the
same drying conditions? (The equilibrium moisture content of
the solid is 5%).
A. 15 min C. 51 min
B. 71 min D. 94 min

58.A composite wall of an oven consists of three materials A, B

and C. Under steady state operating conditions, the outer
surface temperature TSo is 20oC. The inner surface temperature
TSi is 600oC and the oven temperature is Too is 800oC. For the
following data: thermal conductivities, KA = 20 W/m-K, Kc =
50 W/m-K; thickness tA = 0.3 m, tB = 0.15 m and tC = 0.15 m;
inner wall heat transfer coefficient, h = 25 W/m2-K. What is
the thermal conductivity KB in W/m-K of material B?
A. 0.03 C. 1.53
B. 0.66 D. 35
59.A diesel power plant uses fuel with heating value of 43,000
kJ/kg. What is the density of the fuel at 25°C?
A. 840 kg/m3 C. 970 kg/m3
B. 873 kg/m 3 D. 940 kg/m3

60.A water main is to be laid from the present pumping station

in a small community to a new subdivision. The estimated
future population of the subdivision is 1500 persons, each of
whom will use an average of 40 gal of water per day, with the
maximum rate of 4 gph. The pipe is to be cast iron. The
subdivision lies on the crest of a low hill whose summit is
75 ft above the pumping station, and the route of the pipe is
13500 ft long to the summit. The pump delivers the maximum
capacity at a head of 145 ft. If the pressure at the summit
must be 25 psig under the maximum flowrate, what pipe size
(inches) is required?
A. 5 in C. 4 in
B. 6 in D. 3 in

61.A sample of natural gas containing 80% Methane (CH4) and the
rest Nitrogen (N2) is burnt with 20% excess air. With 80% of
the combustibles producing CO2 and the remainder going to CO,
the volume percent of N2 in the Orsat analysis is
A. 86% C. 95%
B. 77% D. 62%

62.Calculate the terminal settling velocity in ft/s in water at

700F of a particle with a specific gravity of 2.0 and diameter
of 100 microns is __ ft/s.
A. 0.05 ft/s C. 0.09 ft/s
B. 0.02 ft/s D. 0.07 ft/s

63.It is desired to supply steam in sauna bath 35 meters above

sea level initially at a temperature and pressure are 3000C
and 500 kPa. The outlet steam supplied to the bath house is
at 2000C and 100 kPa to compensate heat losses along the pipe
line. As such, the outlet velocity of steam must be three
time as fast as the inlet steam velocity to neglect heat
losses. If 16 kW pump is available, calculate the mass flow
rate of steam to be supplied from a 6 cm pipe diameter in
kg/s.
A. 2.5 kg/s C. 1.3 kg/s
B. 1.8 kg/s D. 2.9 kg/s

64.A centrifugal pump is used to pump water through a horizontal

distance of 150 m and then raised to an overhead tank 10 m
above. The pipe is smooth with an I.D. of 50 mm. What head
(m of water) must the pump generate at its exit (E) to deliver
water at a flow rate of 0.001 m3 /s? The Fanning friction
factor, f is 0.0062.
A. 15 C. 26
B. 11 D. 20

65.A relatively pure saturated hydrocarbon gas is being burnt

with air in a small furnace. A sample of the flue gas is
taken, and a portion is subjected to analysis in a standard
Orsat apparatus. The date obtained are as follows (in mL):
initial volume of sample – 100.0; after caustic absorption –
92.6; after pyrogallol absorption – 87.1; after cuprous
chloride absorption – 83.4. On the basis of this analysis,
what is the hydrocarbon being burnt?
A. methane C. propane
B. ethane D. butane
66.A reversible non-flow expansion process occurs from which the
work 9.4 BTU. If the pressure varies as P = -V2 + 100/V, where
P is in psia and V is in ft3 and P1 = 46 psia. Find P2 in psia.
A. 28 psia C. 8.7 psia
B. 12.1 psia D. none of these

67.A horizontal tubular type of boiler uses crude oil consisting

substantially of hydrocarbons. Th oil is available at 700F
and has a specific gravity of 8.90 and viscosity of 58 cP. In
actual operation, water is fed to the boiler at a temperature
600F and vaporized to form steam at a gauge pressure of 100
psi and 98% quality of steam at a steam generation rate of 10
lb of steam per lb of oil fired. The average analysis of the
flue gases is as follows: CO2 = 11%; CO = 0.5%; O2 = 6%; and
N2 = 82.5%. At normal running rate the boiler generates 3450
lb of steam per hour. If the boiler water is available from
a well 30 ft below the feed line and the water line consists
of 200 ft (total and equivalent) of 1-in standard steel pipe,
what horsepower pump should be used if the efficiency of the
pump is only 50%? The oil feed comes from a reservoir under
a suitable head. The feed line consists of standard 3/4 in
steel pipe.
A. 6.9 hp C. 7.7 hp
B. 5.2 hp D. 4.8 hp

68.A counter-current leaching system is to treat 10 kg/h of

crushed sugar stalks with impurity-free water as solvent.
Analysis of the stalks is as follows: 38% by mass water, 10%
sugar, 52% pulp. If 95% of sugar is to be recovered and the
extract phase leaving the system is to contain 12% sugar,
determine the number of actual stages required if each
kilogram of the dry pulp retains 2.5 kg of the solution.
Assume an over-all stage efficiency of 85%.
A. 10 C. 14
B. 12 D. 16

69.In an Otto cycle, state 1 at the beginning of compression is

13.8 psia, 100°F, 1 cu. ft. After compression to 250 psia, 80
Btu/cycle are added. Using an average Cp/Cv = 1.31 for the
hot air standard, find the mean effective pressure.
A. 180 psia C. 350 psia
B. 92 psia D. 240 psia

70.A spherical, thin-walled metallic container is used to store

nitrogen at 77 K. The container has a diameter of 0.5 m and
is covered with an evacuated, reflective insulation composed
of silica powder. The insulation is 25 mm thick, and its outer
surface is exposed to ambient air at 300 K. The convection
coefficient is known to be 20 W/m2·K. The latent heat of
vaporization and the density of liquid nitrogen are 2x105 J/kg
and 804 kg/cu m, respectively. What is the daily rate of
liquid boil-off in liters?
A. 7 L/d C. 2 L/d
B. 9 L/d D. 5 L/d

71.During a polytropic compression, 3 lb of nitrogen are

compressed from 14 psia and 600F while 75 BTU of heat are
rejected. For PV1.32 is constant, calculate the entropy change
in BTU/R.
A. -0.086 BTU/R C. -0.098 BTU/R
B. -0.077 BTU/R D. -0.060 BTU/R
72.Around airports jet aircrafts can become major contributors
to pollution, and as aircraft activity increases and public
concern brings other sources under control, the relative
contribution of aircraft to pollution could go up. Recently,
federal-, state-, and local government pressure has speeded
the introduction of new combustors in aircraft. In a test for
an aircraft fuel with the average composition C1.20H4.40, the
fuel is completely burned with the exact stochiometric amount
of air required. The air is supplied at 24°C and 100 kPa,
with a humidity of 80 percent. For the entering air, compute
the dew point.
A. 180C C. 200C
B. 22 C
0 D. 150C

73.A simple vacuum crystallizer is to produce 10000 lb copperas

crystals per hour. The feed is a solution containing 38.9
parts solute per 100 parts total water, and it enters the
crystallizer at 158 0F. The crystallizer vacuum is such as to
produce a crystallizer temperature of 80 0F. Saturated
solution at 80 0F contains 30.2 parts of solute per 100 parts
total water. The enthalpies of saturated solution, the
crystals leaving the crystallizer, the feed and vapor are: HL
= -2.4 BTU / lb, HC = -91 BTU / lb, HF = 48.6 BTU / lb and HV
= 1096 BTU / lb. Determine the feed needed in lbs.
A. 50000 lb C. 36000 lb
B. 48000 lb D. none of these

74.Dry air at 295 K and 100 kPa is bubbled through benzene. If

the saturated air leaves at 300 K and 100 kPa, how many
kilograms of benzene are evaporated per 100 m3 of entering
air? The vapor pressure of benzene (kPa) is given by ln P =
13.8858 – 2788.51/(T -52.36)
A. 40 kg C. 51 kg
B. 68 kg D. 77 kg

75.A solution is to be concentrated from 10% to 65% solids in a

vertical long tube evaporator. The solution has a negligible
elevation of boiling point and its specific heat can be taken
to be the same as that of water. Steam is available at 203.6
kPa, and the condenser operates at 13.33 kPa. The feed enters
the evaporator at 295 K. The total evaporation is to be 25,000
kg/h of water. The overall heat transfer coefficient is 2800
W/m2-K. Calculate the heat-transfer surface area of the
evaporator.
A. 35.1 m2 C. 65.5 m2
B. 45.2 m2 D. 90.7 m2