PROBLEMS TO MEMORIZE

Question 1

The distance of the Earth to the most remote
normal galaxy is calculated to be:

Answer 1

2x10^22 m

Question 2

Determine the oxidation number of
Chromium in CrF6 3+
.
A. 2 C. 5
B. 3 D. 6

Answer 2

B. 3

Question 3

In order to describe the intensive state of a system at
equilibrium, specify the degrees of freedom for a onephase, two-phase and three-phase system.

A. F=2, F=1, and F=0
B. F=1, F=2, and F=3
C. F=0, F=1, and F=2
D. F=3, F=2, and F=1

Answer 3

A. F=2, F=1, and F=0

Question 4

(Oct. 2021 PBE) A certain volume of a
solution of KMnO4 will oxidize sufficient
potassium tetraoxalate that requires half of
that volume using 0.201N of KOH solution
for neutralization. Determine the quantity
of KMnO4 in a liter of its solution.

a. 4.213g
b. 2.01g
c. 8.621g
d. 5.02g

Answer 4

b. 2.01g

Question 5

Determine the number of days it will take for one
milligram of rubidium to decay to 0.6 mg.

A. 132
B. 98
C. 63
D. 211

Answer 5

C. 63

Question 6

A waste is being discharged into a river that
has a temperature of 100C. What fraction of
the maximum oxygen consumption has
occurred in 4 days if the BOD rate constant
k, determined in the laboratory under
standard conditions is 0.115/d?

Answer 6

0.12

Question 7

Compute the theoretical NBOD of a
wastewater containing 30 mg/L of ammonia
as nitrogen. If the wastewater analysis was
reported as 30 mg/L of ammonia (NH3
), what would the theoretical NBOD be?

Answer 7

137 mg/L and 113 mg/L

Question 8

Given the following data for Marikina River and Pasig
River, determine the best combination of plant and
location to conserve the environment.

Answer 8

Plant B in Marikina River (HIGHEST DO)

Question 9

A power plant in a college town is burning coal on
a cold, clear winter morning at 8:00 A.M. with a
wind speed of 2.6 m · s
−1 measured at 30 m elevation and an inversion layer with its base at a
height of 697 m. The effective stack height is 30 m. Calculate the distance downwind XL at which the plume released will reach the inversion layer and begin to mix downward.

Answer 9

5.8 km

Question 10

A town of 20,000 in Laguna generates 0.96 kg/(capita)-day of MSW.
A town of the same size in the Makati City in Metro Manila
generates 1.9 kg/(capita)-day of MSW.
How much MSW is generated in each town?
How many trucks would be needed to collect the waste twice
weekly? The trucks each have a capacity of 4.5 MT and operate 5
days per week. Assume that the trucks average two loads per day
at 75% capacity. Calculate the number and volume of MSW in tons
that enter the landfill

Answer 10

4 AND 8 TRUCKS

Question 11

The Nairyosangha landfill located in Peshdadians
serves a population of 562,400 people generating
MSW at a rate of 1.89 kg · capita−1
· day. The
volume of the landfill is 11,240,000 m3
. At the
present time, 63% of the landfill is used. The ratio
of cover to compacted fill is 1.9. Determine
projected life remaining for the landfill. Assume the
density of the compacted waste to be 490 kg · m−3
.

Answer 11

2.76 years

Question 12

A landfill with a gas collection system is in operation and serves a
population of 200,000. MSW is generated at a rate of 1.95 kg ·
(capita)−1
· day−1
. Gas is produced at an annual rate of 6.2 L · kg−1 of
MSW delivered to the landfill. The gas contains 55% methane. Gas
recovery is 15% of that generated. The heat content of the landfill gas
is approximately 17,000 kJ · m−3
(a value lower than the theoretical
value because of dilution of the methane with air during recovery). The
landfill company and a developer have proposed to build a subdivision
in the vicinity of the landfill and pipe the methane generated to the
homes to be used for heating. The homes are estimated to use an
average of 110 × 106 kJ of heat energy each year. Peak usage during
winter is 1.5 times the average usage. How many homes can be built in
the subdivision?

Answer 12

7 homes

Question 13

A solution of HOCl is prepared in water by
adding 15 mg HOCl to a volumetric flask,
and adding water to the 1-L mark. The final
pH is measured to be 7.0. What are the
concentrations of HOCl and OCl? What
percent of the HOCl is dissociated? Assume
the temperature is 250C

Answer 13

[OCl-] = 6.39x10-5 M, [HOCl] =2.22x10-4 M, 22.4%

Question 14

One mole of A at one bar and one mole of B
at 2 bar are separated by a partition and
surrounded by a heart reservoir. Determine
the change in entropy when partition is
withdrawn.
A. 15.24 J/K/mol C. 8.61 J/K/mol
B. 12.50 J/K/mol D. 18.51 J/K/mol

Answer 14

B. 12.50 J/K/mol

Question 15

An inverted T object composed of two identical rectangles with 2” width
and 6” length. What is the moment of inertia about its central axis?
a. 460 in4 c. 320 in4
b. 290 in4 d. 170 in4

Answer 15

b. 290 in4

Question 16

There is a radial clearance of 0.05 mm when a steel tube with
inside diameter of 125.1 mm is placed over an aluminum tube. The
inside diameter of the aluminum tube is 120 mm, and the wall
thickness is 2.5 mm. The aluminum tube is subjected to an internal
pressure of 5 MPa. Use E = 70 GPa for aluminum and E = 200 Gpa
for steel.

80. What is the internal pressure of the aluminum tube to cause
    contact with the steel?

A. 3.003 MPa C. 2.224 MPa
B. 2.381 MPa D. 4.762 MPa

81. What is the contact pressure between steel and aluminum tubes
    when the aluminum tube is subjected to an internal pressure of 5
    MPa?

A. 2.50 MPa C. 2.38 MPa
B. 3.56 MPa D. 5.00 MPa

Answer 16

B. 2.381 MPa
B. 3.56 MPa

Question 17

Block A supports a load W = 100 kN and is to be raised by forcing the
200-wedge B under it. The angle of friction for all surfaces in contact
is f = 15°. If the wedge had a weight of 40 kN, what value of P would
be required

32. To start the wedge under the block and
    a. 110 kN c. 130 kN
    b. 140 kN d. 150 kN
33. To pull the wedge out from under the block?
    a. 49 kN c. 15 kN
    b. 28 kN d. 33 kN

Answer 17

c. 130 kN
b. 28 kN

Question 18

It is desired to separate 1 kg/s of an ammonia solution containing 30
per cent NH3 by mass into 99.5 per cent liquid NH3 and a residual weak
solution containing 10 per cent NH3. Assuming the feed to be at its
boiling point, a column pressure of 1013 kN/m2, a plate efficiency of 60
per cent and that an 8 per cent excess over the minimum reflux
requirements is used.

80. How many plates must be used in the column?
    a. 10 c. 9
    b. 7 d. 12
81. How much heat is removed in the condenser?
    a. 372 kW c. 826 kW
    b. 509 kW d. 617 kW
82. How much heat is added in the boiler?
    a. 372 kW c. 826 kW
    b. 509 kW d. 617 kW

Answer 18

b. 7
a. 372 kW
d. 617 kW

Question 19

A dry pharmaceutical product is prepared at 15% aqueous solution, evaporated
and dried in a vacuum drier. The capacity of the drier varies with the water content
fed from the evaporator discharge. The annual fixed cost for the evaporator and
drum drier related to the solid content S fed to the drier for 300 days per year
operation as follows:
Cf = 6000 (S-0.15)0.5 + 2965 (1-S) $/yr
The direct costs for the evaporator are $0.001 per pound of water evaporated and
$0.003 per pound of water removed in the drum drier. Determine the optimum
concentration of slurry from the evaporator for a production of 3 tons/d solution
fed to the evaporator.
A. 0.42 C. 0.65
B. 0.58 D. 0.77

Answer 19

C. 0.65

Question 20

Naphthenic material is to be removed from lubricating oil by solvent extraction with phenol in a perforated plate using gravity flow. The fixed cost for solvent to charge ratio R has been found to vary according to the equation Cf =9300 (R-32+ 25000 dollars/year, where R = bbl solvent per bbl of feed. The direct cost varies with the amount of solvent redistilled at a rate of $0.20 per bbl of solvent which includes solvent make-up.

50. If the charge stock of 300 bbl per day is to be processed 320 days per year, what is the economical solvent to charge ratio?
    A. 1.65 C. 2.58
    B. 1.97 D. 2.66
51. If the allowable velocity is 50 ft/hr based on the combined flow of pure solvent and charge, what is the tower diameter?
    A. 2.3 ft C. 1.9 ft
    B. 3.0 ft D. 4.5 ft

Answer 20

B. 1.97
A. 2.3 ft

Question 21

A dilute salt solution containing 6% salt is fed to an evaporator at a rate
of 10000 kg/h for a trial run. Crystals formed along with the saturated solution adhering with them are sent to a centrifuge for the recovery of the solution. 60% of the adhering solution is recovered. It is found that the saturated solution that is withdrawn from the evaporator is 850 kg and that is recovered by centrifuging is 200 kg. The crystals are dried to drive off the remaining water. The dry crystals obtained weighed 360 kg. Determine the amount of water removed in the drier.
A. 116 kg C. 103 kg
B. 128 kg D. 135 kg

Answer 21

C. 103 kg

Question 22

A petroleum product of viscosity 0.5 mNs/m2 and density 700 kg/m3 is
pumped through a pipe of 0.15 m diameter to a storage tanks situated 100 m away. The pressure drop along the pipeline is 70 kN/m2. The pipeline has to be repaired and it necessary to pump the liquid by an alternative route consisting of 70 m of 200 mm pipe followed by 50 m of 100 mm pipe.

62. Calculate the velocity in the 0.1 m diameter pipe.
    a. 9.4 m/s c. 1.5 m/s
    b. 3.6 m/s d. 7.2 m/s
63. What is the pressure drop through alternative pipe system?
    a. 390 kPa c. 250 kPa
    b. 180 kPa d. 440 kPa
64. If the existing pump is capable of developing a pressure of 300 kN/m2,
    will it suitable for use during the period required for the repairs?
    Take the roughness of the pipe surface as 0.05 mm.
    a. Yes c. Either (a) or (b)
    b. No d. Cannot be determined

Answer 22

a. 9.4 m/s
c. 250 kPa
a. Yes

Question 23

A sewage lagoon that has a surface area of 10 ha and a depth
of 1 m is receiving 8640 m^3 d^- of sewage containing 100 mg
· L^- of biodegradable contaminant. At steady state, the
effluent from the lagoon must not exceed 20mg· L^- of
biodegradable contaminant. Assuming the lagoon is well mixed
and that there are no losses or gains of water in the lagoon
other than the sewage input, what biodegradation reaction
rate coefficient (d^-) must be achieved for a first-order
reaction?

A. 0.35 C. 0.50
B. 0.22 D. 0.49

Answer 23

A. 0.35

Question 24

The Alangilan Barangay Council in Batangas City has asked
you to determine whether the discharge of the barangay’s
wastewater into the Calumpang River will reduce the DO below
the standard of 5.00 mg/L at Poblacion 5.79 km downstream,
or at any other point downstream. The pertinent data are as
follows:

Given table:

At 28 deg C, DOs = 7.92 mg/L. Calculate the following:

The dissolved oxygen at Poblacion.
A. 5.12 mg/L C. 6.06 mg/L
B. 3.25 mg/L D. 4.75 mg/L

Answer 24

D. 4.75 mg/L

Question 25

In a solution supersaturated with CO3-2 and Ca2, what is the
final concentration of Ca+2 per liter of solution at
equilibrium Ksp CaCO3 (s) = 8.30 (use the quadratic formula)?
A. 16.7 mg/L C. 15.6 mg/L
B. 14.4 mg/L D. 17.0 mg/L

Answer 25

A. 16.7 mg/L

Question 26

A flowing stream has an oxygen deficiency of 6 mg/L. However,
miles downstream the deficiency was reduced to 4 mg/L through
atmospheric absorption. If the stream has a velocity of 2
mph and contains no BOD and other stream conditions are
uniform through its length, estimate the oxygen deficit some
35 miles downstream from the original point.
A. 3.22 mg/L C. 1.46 mg/L
B. 4.14 mg/L D. 2.11 mg/L

Answer 26

C. 1.46 mg/L