MECE Flashcards by ayel cross

Particle diameter representation which is defined as the width of the minimum
square aperture through which the particle will pass.
a. Feret’s diameter
b. Martin’s diameter
c. Sieve diameter
d. Projected area diameter

c. Sieve diameter

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Equivalent diameter of a particle which is referred to the average distance between
pairs of parallel tangents to the projected outline of the particle.
a. Feret’s diameter
b. Martin’s diameter
c. Sieve diameter
d. Projected area diameter

a. Feret’s diameter

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Which of the following is not a standard in a particle size distribution using sieves?
a. Tyler series
b. API
c. US series ATM
d. all are standards

b. API

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In Moh’s scale, which is the hardest among the materials given?
a. Apatite
b. Quartz
c. Feldspar
d. Topaz

d. Topaz

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A crushed material of certain ore has 3’’ – diameter particle and has density of 170lb/ft. If the specific surface area ratio is 10, what is the specific surface in cm² per g of ore?

2.89

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The energy required to reduce the size of a certain ore from 1cm to 0.3cm is 11kJ/kg. What is the power requirement to reduce the same set of material from 0.1cm to 0.01cm assuming Kick’s law apply?

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What is the sphericity of cylinder assuming that the equivalent length is equivalent
to its height?

0.874

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In an analysis of a certain crushed material, the total surface area of a certain
fraction of a 5kg sample that passed through a 7 mesh sieve but was caught on a 9 mesh sieve is 7.88m². If the density of the material is 1050 kg/m³ and the shape factor is 1.75, find the fraction.

38%

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What is the sphericity of a cylinder with L/D ratio of 1?

0.874

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What is the sphericity of a cube?

0.806

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Find the width of an apron conveyor without skirts whose capacity is 56tons/hr at a speed of 50rpm handling solids with density of 50lb/cuft.

36 inches

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A type of a gas-solid separator employing centrifugal force.
a. elutriator
b. cyclones
c. centrifuge
d. none of these

Cyclones

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The energy required per unit mass to grind limestone particles of very large size to
100mm is 12kWh/ton. An estimate (using Bond’s law) of the energy to grind the particles from a very large size to 50mm is

18 kwh/ton

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A material is crush in a Blake Jaw Crusher and the average size of particle reduces
from 50mm to 10mm with the consumption of energy at the rate of 13kW(kg/s). The consumption of energy needed to crush the same material of an material of an average size 75mm to an average size 25mm assuming Kick’s Law applies is

8.88kW (kg/s)

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Saturated steam at 110⁰C is available and the temperature in the condenser is 43⁰C.
Specific heat of the solutions may be taken is constant at 4 J/g ⁰C. The overall-heat transfer coefficient is 2840W/m² ⁰C. Determine the steam consumption, in kg/hr.

3400

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Determine the boiling point rise for the following solutions
of biological solutions in water. A 30 wt% solution of citric acid in water boiling at 220⁰F

2.2⁰F

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Determine the boiling point rise for the following solutions of biological solutions in water. A 40 wt% solution of sucrose in water boiling at 220⁰F

2.1⁰F

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The rate of increase of the number of bacteria under certain condition is proportional to the number of bacteria. If the number doubles in four hours, how much increase in number of bacteria can be expelled after 12 hours?

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A second order reaction involving reactants initially present at 0.10moles/L is
found to be 20% complete in 40minutes, when the reaction is 25⁰C, and 40% complete in 35 minutes, when the reaction is 50⁰C. What is the activation energy for this reaction in cal/mol?

8500 cal/mol

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In a first order reaction the time required to reduce the concentration of reactant
from 1mol/L to 0.5mol/L will be _____________ that required to reduce it from 10mol/L to 5mol/L in the same volume.
a. more than
b. less than
c. same
d. data sufficient

c. same

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If a first order reversible liquid reaction A ↔ B is conducted in a batch reactor. The initial concentrations are 𝐶𝐴0= 0.5gmol/L and 𝐶𝐵0 = 0. After 8 minutes, the fractional conversion of A is 1/3 and at equilibrium, the fractional conversion of 2/3. Find the equilibrium constant.

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A gaseous reaction, A → 2B + C takes place isothermally in a constant pressure reactor. Starting with gaseous mixture containing 50% A, the ratio of final to initial volume is found to be 1.6. Calculate the percentage conversion of A.

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Pick the wrong statement pertaining to space velocity of flow reactors.
a. The unit space velocity is (𝑡𝑖𝑚𝑒)−1.
b. The space velocity of 3 ℎ𝑟−1 means that the three reactor volumes of feed at
specified conditions are being fed into the reactor every hour.
c. The space velocity of 3 ℎ𝑟−1 means that the one third reactor volume of feed at
specified conditions are being fed into the reactor.
d. None of these.

c. The space velocity of 3 ℎ𝑟−1 means that the one third reactor volume of feed at
specified conditions are being fed into the reactor.

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For liquid phase zero order irreversible reaction A → B, the conversion of A in a CSTR is found to be 0.3 at space velocity of 0.1𝑚𝑖𝑛−1. What will be the conversion for PFR with a space velocity of 0.2𝑚𝑖𝑛−1? Assume that all the other operating conditions are the same for CSTR and PFR.

0.15

A homogenous liquid phase, A → R, −𝑟𝐴 = 𝑘𝐶𝐴² takes place with 50% conversion in a mixed reactor. The value of space time a. 1/(2k𝐶𝐴0) b. 2/(𝑘𝐶𝐴0) c. 1/(k𝐶𝐴0) d. 3/(k𝐶𝐴0)

b. 2/(𝑘𝐶𝐴0)

A homogenous liquid phase, A → R, −𝑟𝐴 = 𝑘𝐶𝐴² takes place with 50% conversion in a mixed reactor. What is the conversion if the reactor is replaced by one 6 times as large – all else remaining unchanged?

0.75

A homogenous liquid phase, A → R, −𝑟𝐴 = 𝑘𝐶𝐴² takes place with 50% conversion in a mixed reactor. Calculate the conversion if the original reactor is replaced by a plug flow reactor of equal size – all else remaining unchanged?

0.67

The separation of solid particles into several size fractions based upon the settling velocities in a medium is called a. settling b. filtration c. flotation d. classification

d. classification

An apparatus in which particles settle in a liquid by gravitational or centrifugal force and are removed as a concentrated slurry. a. classifier b. thickener c. elutriator d. agitator

b. thickener

Which of the following sets of reversible processes describes an ideal Otto cycle? I. Adiabatic compression, constant volume heat addition, adiabatic expansion, constant volume heat rejection II. Isothermal compression, isobaric heat addition, isothermal expansion, isobaric heat rejection a. I only b. II only c. I and II in succession d. II and I in succession

a. I only

What is the absolute velocity of a real fluid at a surface? a. the same as the bulk fluid velocity b. the velocity of the surface c. zero. d. proportional to the smoothness of the surface

b. the velocity of the surface

Which of the following statements regarding Rankine cycles is false? a. Use of condensable vapor in the cycle increases the efficiency of the cycle b. The temperatures at which energy is transferred to and from the working liquid are less separated than in a Carnot cycle c. Superheating increases the efficiency of a Rankine cycle d. In practical terms, the susceptibility of the engine materials to corrosion is not a key limitation on the operating efficiency.

d. In practical terms, the susceptibility of the engine materials to corrosion is not a key limitation on the operating efficiency.

Which of the following is/are representation of a carnot cycle? a. I and II b. I and III c. II and III d. all of these

c. II and III

For which type of process is the equation dQ = TdS valid? a. Irreversible b. Reversible c. Isothermal d. Isobaric

b. Reversible

The general energy equation for an open system involves the following terms: I. Accumulation of energy II. Net energy transfer by work III. Net energy transfer by heat IV. Transfer of energy in by mass flow V. Transfer of energy out by mass flow a. I = -II + III + IV – V b. I = II + III + IV + V c. I = II + III + IV – V d. I = II – III – IV + V

a. I = -II + III + IV – V

Which of the following flow meters measure/s the average fluid velocity rather than a point or local velocity in a pipe? I. Venturi meter II. Pitot tube III. Impact tube IV. Orifice meter V. Hot-wire anemometer a. I and III b. III and V c. I and IV d. II and V

c. I and IV

Consider the following two flows of water in the figure shown. What is the relation between the velocity at point 2 in I and II? a. V2(I) =V2(II) b. V2(I) =1/2 V2(II) c. V2(I) =2 V2(II) d. V2(I) =4 V2(II)

a. V2(I) =V2(II)

Which of the following describes a streamline? I. It is a mathematical concept II. It cannot be crossed by the flow III. It is a line of constant entropy a. I and II b. I and III c. II and III d. all of these

a. I and II

Calculate the terminal velocity of a steel ball, 2mm diameter and of density 7870kg/m³ in an oil of density of 900kg/m³ and viscosity 50mN-s/m².

0.189 m/s

The thermodynamic equilibrium constant is unaffected by the following except: a. Pressure of the system b. Presence or absence of inerts c. velocity of the flow d. kinetics of the reaction

c. velocity of the flow

He pioneered the work of the first commercial steam turbine (5hp). a. George Herman Babcock b. Stephen Wilcox c. Gustaf de Laval d. John Barber

c. Gustaf de Laval

Power plants should operate on the following conditions: a. below 100,000kPa and below 600⁰C b. below 100,000kPa and above 600⁰C c. above 100,000kPa and above 600⁰C d. above 100,000kPa and below 600⁰C

a. below 100,000kPa and below 600⁰C

The Diesel engine differs from the Otto engine because a. higher compression ratio b. lower compression ratio c. low cut-off ratio d. high cut-off ratio

a. higher compression ratio

Air is flowing at a steady rate of 0.0232 lb/sec through a straight tube having an inside diameter of 0.2 inch. At the first section, the air has a temperature of 70⁰F and is under an absolute pressure of 0.2atm. The tube is heated and the net input power, between the first and second section, is 174 watts. The air at the second section is under an absolute pressure of 0.1atm. The average specific heat of the air is 0.24BTU/lb ⁰F. Calculate the temperature of the air leaving the second section.

73⁰F

A tank of relatively non-volatile oil is to be cooled from 200⁰ to 100⁰C by blowing cold air at 1 atm and 20⁰C through it. How long will this process take if the air leaving the tank is always in thermal equilibrium with the oil? Assume that the air bubbles keep the oil well agitated. Data: Heat capacity of oil = 0.81 cal/(g ⁰C) Air rate (1 atm and 20⁰C) = 100cfm Capacity of the oil tank = 1,000 gal Sp. Gr of oil = 0.88

4550 min

A very dilute gas mixture of sulfur dioxide in air is contacted with water in a 25 mm ID wetted wall column at 20⁰C and 1 atm. The velocity of gas mixture is 2.2m/s. Determine the friction factor.

0.08

The rotational speed in RPM that you could recommend for a ball mill, 1200 mm in diameter charged with 75 mm balls is

In countercurrent liquid-liquid extraction, the maximum concentration of solute in extract layer a. Is that corresponding to equilibrium with the incoming feed b. Is less that the concentration corresponding to equilibrium with the incoming feed c. Can be increased than the obtained in (a) above by using raffinate reflux d. none of the above

a. Is that corresponding to equilibrium with the incoming feed

An isobaric steam generating process starts with saturated liquid at 143kPa. The change in entropy is equal to the initial entropy. Not all of the liquid is vaporized. What is mostly nearly the change in enthalpy during the process?

540 kJ/kg

A current of 200A is passed through a stainless steel wire ( k =22.5, SI units) with a diameter of 5mm and length of 1 m. The electrical resistance of the wire is 0.1ohm. Estimate the temperature at the center of the wire if the outer surface temperature is held at 114⁰C

128.4deg C

What is the BPR of a 30% NaOH solution at an evaporator pressure of 3.722psia?

25 deg F

A system consists of moist air and water inside a closed container. What is this system’s degree of freedom?

A newly designed air-conditioning unit has a capacity of 3140 watts and an input rating of 735 watts. If this machine is operated as heat pump, its COP is

5.27

The evidence that the solute does not freeze with the solvent is that: a. the first crystals formed are precipitates of the solute b. the crystals formed could clearly be seen as that of the solution c. the freezing point of the solution that remains a liquid is getting lower and lower as freezing proceeds d. the freezing point asymptotically a constant value.

c. the freezing point of the solution that remains a liquid is getting lower and lower as freezing proceeds

What does the dashed curve in the figure represent? a. the solidus line b. an isotherm c. the saturated liquid line d. the saturated vapor line

d. the saturated vapor line

For the Carnot cycle shown, helium is the gas used with a specific heat ratio, k, of 5/3. Given that 𝑉𝐵 /𝑉𝐴=2 and 𝑇𝐴 /𝑇𝐷=1.9, calculate 𝑃𝐶/𝑃𝐴 .

0.100

Pick out the wrong statement. a. entering velocity of the liquid in the tubes of natural circulation evaporators is in the range of 0.3 to 0.9m/s. b. duhring’s plot is used for calculating the concentration of solution c. the value of hydrostatic head increases with increase in vacuum in the effect in a multiple effect evaporator system d. In a multiple effect evaporator system, the number of effects is limited by the total boiling point rise.

b. duhring’s plot is used for calculating the concentration of solution

Which of the following has the minimum absorptivity? a. Refractory bricks b. Aluminum foil c. Iron plates d. Coal dust

b. Aluminum foil

To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is a. 1-1 heat exchanger b. 1-2, heat exchanger c. 2-4, heat exchanger d. 3-2 heat exchanger

a. 1-1 heat exchanger

Drying operation under vacuum is carried out to a. reduce drying temperature b. dry those materials which have very high unbound moisture content c. dry materials having high bound moisture content d. increase drying temperature

a. reduce drying temperature

Pick out the wrong statement. a. 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. b. Packed towers are preferred over plate towers for handling corrosive and foamy liquids. c. due to uneven supply and improper distribution of liquid, problem of channeling, loading & flooding is generally encountered in packed towers. d. diameter of randomly packed towers is normally more than 1.2m.

D. diameter of randomly packed towers is normally more than 1.2m

For zero order reaction, the concentration of product increases with the a. increase of reaction time b. total pressure c. increase in initial concentration d. decrease in total pressure

a. increase of reaction time

Which of the following curves shows the effect of temperature on the gas-solid adsorption at a given pressure? a. Freundlich adsorption isotherm b. Adsorption isobar c. Langmuir adsorption isotherm d. None of these

b. Adsorption isobar

Pick out the wrong statement. a. In a continuous flow reactor, uniform concentration can not be maintained throughout the vessel even in a well agitated system b. In a continuous flow reactor, both the reactants and products flow out continuously. c. In a semi-batch reactor, one reactant is charged otherwise, while the other reactant is fed continuously. d. In a batch reactor, which is exclusively used for liquid phase reactions; temperature pressure and composition may vary with time.

A. In a continuous flow reactor, uniform concentration can not be maintained throughout the vessel even in a well agitated system

Which of the following denotes the effect of compressibility in fluid flow? a. Weber number b. Euler number c. Reynolds number d. Mach number

d. Mach number

Pick out the wrong statement pertaining to the design of the bubble cap tray of a distillation column to give stable operation and even vapor distribution. a. the dimensionless ratio of liquid gradient to pressure drop head caused by the bubble cap assembly should be less than 0.4. b. the pressure drop due to the caps and slots and the static submergence should be as high as practicable for reasonable operation c. Tendency towards stable operation is increased by increasing the skirt clearance of the caps, lowering the rate of liquid flow per unit plate width or increasing the spacing between the caps. d. none of these

D. None of these

It is the procedure in which a fraction of the fees to a process unit is diverted around the unit and combined with the output stream from the unit. a. Recycle b. Bypass c. Purge d. Reflux

b. Bypass

A storage tank of demineralized water has a holding capacity of 1800m3 up to an overflow point. The DM water having silica content of 0.005mg/L is flowing into a tank at a rate of 25L/s. The outflow from a tank to the high pressure boiler is 25L/s. With time, the quantity of DM water deteriorates and the silica content rose up to 0.02mg/L. Assuming that the inflow and the outflow remains constant, determine the time in hrs required for the silica content in the storage tank to increase to 0.01mg/L.

8.11

One gram of a magnesium-aluminum alloy was reacted with excess muriatic acid to form magnesium chloride, aluminum chloride and hydrogen gas. Hydrogen gas collected over mercury at 0⁰C occupied at 2.835L at 39.26kPa. Find the %Al in the alloy.

The fresh feed to the process was 0.5kmol/hr of O2 and an excess methanol. All of the O2 reacts in the reactor. Formaldehyde and water are removed from the product stream first, after which H2 is removed from the recycled methanol. The recycle flow rate of methanol was 1kmol/hr. The ratio of methanol reacting by decomposition to that by oxidation was 3. Calculate the per pass conversion in % of methanol in the reactor

Natural gas containing 80% CH4, 15% C2H6, and 5% C3H8 is burnt with 50% excess air. Assuming that 90% of the carbon in the hydrocarbons are converted to CO2 and the rest to CO, determine the %mol of H2O produced in stack gas.

2.25

A solid fuel consisting of 90.04% C, 0.79% S, 1.2%N with no ash and moisture undergoes combustion with excess air. Analysis of stack gas shows 10.83% CO2, 1.08% CO, 0.22%H2, 79.9%N2 and 7.97%O2. Calculate the ultimate H in the solid fuel.

5.39

The most matured coal out of the following is a. Bituminous b. Semi-anthracite c. Sub-bituminous d. Lignite

b. Semi-anthracite

Gross calorific value will be equal to the net calorific value for a. H2 b. C2H2 c. CO d. C2H6

c. CO

A fluid flow (Cp = 4.0kJ/kg-K) flowing at 0.5kg/s is to be heated from 18⁰C to 30⁰C in a medium sized 2-3 STHE using another fluid (Cp = 1.20kJ/kg-K), which enters on the shell side of the exchanger at 71⁰C and to leave at 62⁰C. The overall heat transfer coefficient is 50W/m²-K. What is the flow rate of the other fluid?

2.2

11.55

Because of fouling due to prolonged use, the exit temperature of the cold fluid becomes 28⁰ a. 0.00669 b. 0.00103 c. 0.000931 d. 0.00483

c. 0.000931

What is the simplest type of heat exchanger? a. Double-pipe HE b. Shell-and-tube HE c. Cross-flow HE d. Finned-type HE

a. Double-pipe HE

In a distillation column, the bottom section has the following characteristics, a. highest temperature b. highest pressure c. both a and b d. neither a nor b

c. both a and b

Minimum reflux of stagrs can be achieved through a. total reflux b. maximum reboiling c. alternate use of tray and packings d. oversized condenser

A. Total reflux

The overall separation efficiency can be dictated by a. relative volatilies b. number of trays c. intimate contact on each tray/stage d. all of the above

D. all of the above

As the temperature of the liquid increases, its vapor pressure tends to a. decrease b. increase c. remain the same d. fluctuate relative to the liquid’s density

B. increase

What is the boiling point of a benzene-toluene mixture under atmospheric pressure if the mixture contains 0.682 mole fraction toluene?

98degC

What is the boiling point of a benzene-toluene mixture under atmospheric pressure if the mixture contains 0.682 mole fraction toluene? When the resulting vapor is condensed, the liquid composition contains how much benzene (mole fraction)?

0.532

What are the advantages of extraction processes compared with other separation processes? a. Extraction is a separation process which involves no evaporation; carried out mostly at ambient temperature and can be used as a separation process for high temperature sensitive products. b. All streams are in liquid phase, therefore the system pressures are lower, resulting in thinner walls needed for the equipments. c. There are no specific advantages. d. The treatment of the process products is easier, since all are in liquid phase. There is no cooling energy needed.

A. Extraction is a separation process which involves no evaporation; carried out mostly at ambient temperature and can be used as a separation process for high temperature sensitive products.

In liquid-liquid extraction 10 kg of a solution containing 2 kg of solute C and 8 kg of solvent A is brought into contact with 10 kg of solvent B. Solvents A and B are completely immiscible in each other whereas solute C is soluble in both the solvents. The extraction process attains equilibrium. The equilibrium relationship between the two phases is Y* = 0.9X where Y* is kg of C/kg of B and X is kg of C/kg of A. Choose the correct answer. a. the entire amount of C is transferred to solvent b. less than 2 kg but more than 1 kg of C is transferred to solvent B c. less than 1 kg of C is transferred to B d. no amount of C is transferred to B

B. less than 2 kg but more than 1 kg of C is transferred to solvent B

Determine the state of water according to the following condition of at 440⁰F with density of 842.3679kg/m³. a. saturated liquid b. saturated vapor c. sub-saturated d. superheated

C. Sub-saturated

A utility runs a Rankine Cycle with a water boiler at 3.5MPa and the cycle has the highest and lowest temperature of 450⁰C and 45⁰C respectively. What is the cycle efficiency?

0.36

MECE Flashcards

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