## Machine Design MCQ Set 1

1. What is the value of emissivity for polished aluminum?

a) 0.01

b) 0.02

c) 0.03

d) 0.04

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2. Which one is having highest emissivity?

a) Tarnished copper

b) Polished aluminum

c) Aluminum foil

d) Polished copper

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3. What is the value of emissivity for polished copper?

a) 0.02

b) 0.03

c) 0.04

d) 0.05

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4. What is the value of emissivity for tarnished copper?

a) 0.78

b) 0.77

c) 0.76

d) 0.75

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5. Which one is having lowest emissivity?

a) Polished stainless steel

b) White marble

c) Snow

d) Asphalt

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6. What is the value of emissivity for dull stainless steel?

a) 0.24

b) 0.23

c) 0.22

d) 0.21

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7. What is the value of emissivity for white marble?

a) 0.96

b) 0.95

c) 0.94

d) 0.93

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8. Which one is having highest emissivity?

a) Red brick

b) Concrete

c) Black paint

d) Dull stainless steel

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9. What is the value of emissivity for asphalt?

a) 0.90

b) 0.80

c) 0.70

d) 0.60

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10. Which one is having lowest emissivity?

a) Snow

b) White marble

c) Concrete

d) Polished stainless steel

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## Machine Design MCQ Set 2

1. Partial pressure equals vapour pressure if it is___________

a) Saturated

b) Unsaturated

c) Isothermal

d) None of the mentioned

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2. Say True or False

I) Vapour- at superheated temperature

II) Gas – at condensation temperature

a) True

b) False

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3. Guess the saturated molar absolute humidity of the gas(A.- Vapour(B. mixture at 100 degree Celsius. Vapour pressure of A is 300 mmHg and the total pressure is 760 mmHg.

a) 0.39

b) 0.65

c) 0.60

d) Cannot determine

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4. The system is unsaturated if partial pressure _________ equilibrium vapour pressure.

a) Less than

b) Greater than

c) Equals to

d) All the mentioned

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5. Consider a saturated gas(A.-vapour(B. mixture , if the absolute molal humidity is 0.265 and the total pressure= 760 mmHg. Find the vapour pressure of B.

a) 149.21 mmHg

b) 159.21 mmHg

c) 169.21 mmHg

d) 600.8 mmHg

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6. The vapour pressure of the nitrogen gas is 400mmHg and the partial pressure is 300mmHg. Find the relative saturation.

a) 75

b) 133

c) 100

d) 50

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7. Thermometer measurement temperature is

a) Dry bulb temperature

b) Wet bulb temperature

c) Dew point temperature

d) Room temperature

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8. Find the dew point

a) X

b) Y

c) Z

d) None of the mentioned

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9. Temperature at which the partial pressure of the gas-vapour mixture equals vapour pressure _______

a) Dry bulb temperature

b) Wet bulb temperature

c) Dew point temperature

d) None of the mentioned

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10. Check whether we get approximately 80% saturation if the total pressure and the partial pressure of the gas mixture is 760 mmHg and 260 mmHg. Also the vapour pressure is 300 mmHg.

a) True

b) False

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## Machine Design MCQ Set 3

1. __________ is the single stage device in extractor types.

a) Mixer settler

b) Sieve trays

c) Agitator vessel

d) Packed column

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2. Settler in the mixer settler is applicable for rapid agitation.

a) True

b) False

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3. The substance to get mixed enters into the mixer through.

a) Orifice

b) Nozzle

c) Orifice or nozzle

d) None of the mentioned

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4. Line mixers are ________

a) Small

b) Large

c) Very high

d) None of the mentioned

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5. The two liquids while mixing gets dispersed inside the mixer.

a) True

b) False

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6. If the holding time is more in a mixer then _______ will be poor.

a) Mass transfer

b) Heat transfer

c) Momentum transfer

d) Both mass and momentum transfer

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7. More than three stages of mixer settler attached to get _____________

a) Multi-component cascade

b) Mixer settler cascade

c) Extraction multi-stages

d) None of the mentioned

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8. The extractor preferred for getting immediate dispersion after piping is ___________________

a) Don extractor

b) Box extractor

c) Boltzmann extractor

d) Immediate dispersion is not possible

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9. If a system has low interfacial tension _________ extractor is preferred.

a) Packed column

b) Pulse column

c) Sieve plates

d) Agitator column

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10. _____________ mixing is applicable for differential contractors.

a) Axial

b) Radial

c) Both axial and radial

d) Not the above mentioned

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11. Packed tower with ________ packing preferable for liquid extraction.

a) Uniform

b) Random

c) Complete

d) None of the mentioned

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12. Motivational force in differential contractor is

a) Centrifugal force

b) Gravitational force

c) Electromagnetic forces

d) All the mentioned

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13. The high density difference among the liquid in the extractor cause ________

a) Flooding

b) Loading

c) Agitation

d) None of the mentioned

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14. Differential contractors are continuous extractor.

a) True

b) False

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15. Find the process.

a) Batch process

b) Continuous process

c) Batch+ continuous process

d) None of the mentioned

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## Machine Design MCQ Set 4

1. Fick’s law is given by the formula

a) N _{b }= – D _{b c }d C _{b}/d x

b) N _{b }= – 2 D _{b c }d C _{b}/d x

c) N _{b }= – 3 D _{b c }d C _{b}/d x

d) N _{b }= – 4 D _{b c }d C _{b}/d x

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2. Figure shows equimolal diffusion between species B and C. Identify the correct molar diffusion rate

a) N _{b }= m _{c}/M _{b}

b) N _{b }= m _{b}/M _{b}

c) N _{c }= m _{b}/M _{b}

d) N _{c }= m _{b}/M _{c}

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3. What is the unit of diffusion coefficient?

a) m^{2}

b) s

c) m^{2 }s

d) m^{2}/s

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4. What is the molecular weight of ammonia?

a) 31

b) 53

c) 29

d) 39

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_{3}.

5. What is the molecular volume of air at normal boiling point?

a) 29.89 cm^{3}/gm mole

b) 39.89 cm^{3}/gm mole

c) 49.89 cm^{3}/gm mole

d) 59.89 cm^{3}/gm mole

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6. What is the value of Schmidt number for hydrogen?

a) 0.23

b) 0.22

c) 0.21

d) 0.21

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7. Estimate the diffusion coefficient for ammonia in air t 25 degree Celsius temperature and one atmospheric pressure.

For ammonia,

Molecular weight = 17

Molecular volume = 25.81 cm^{3}/gm mole

For air,

Molecular weight = 29

a) 0.4880 cm^{2}/s

b) 0.3880 cm^{2}/s

c) 0.2880 cm^{2}/s

d) 0.1880 cm^{2}/s

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^{3/2}/p

_{t}(V

_{b}

^{1/3}

_{ }+ V

_{c}

^{1/3})

^{2 }[1/M

_{b }+ M

_{c}]

^{ ½}.

8. Estimate the diffusion coefficient of carbon monoxide through air in which the mole fractions of each constituents are

O _{2} = 0.18

N _{2} = 0.72

CO = 0.10

The gas mixture is at 300 K and 2 atmosphere total pressure. The diffusivity values are

D _{CO }= 18.5 * 10 ^{-6 }m^{2}/s at 273 K, 1 atm

D _{CN }= 19.2 * 10 ^{-6 }m^{2}/s at 288 K, 1 atm

The subscripts C is carbon monoxide, O is oxygen and N is nitrogen

a) 10.29 * 10 ^{-6 }m^{2}/s

b) 18.5 * 10 ^{-6} m^{2}/s

c) 17.5 * 10 ^{-6 }m^{2}/s

d) 13.5 * 10 ^{-6 }m^{2}/s

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_{1}/T

_{2})

^{ 3/2 }(p

_{2}/p

_{1}) = D

_{1}/D

_{2}.

9. What is the molecular weight of Sulphur-dioxide?

a) 84

b) 74

c) 64

d) 54

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_{2}.

10. The dimension of diffusion coefficient is given by

a) M L T ^{-2}

b) L ^{2 }T ^{-1}

c) L T ^{-1}

d) M L ^{-2 }T

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^{2}/s.

## Machine Design MCQ Set 5

1. For what kind of mixtures D_{AB}=D_{BA} holds?

a) Ideal

b) Real

c) For both real and ideal

d) This relation is never true.

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2. In the expression for molar flux N_{A}=(N_{A}+N_{B})C_{A}/C – D_{AB}dC_{A}/dz, the terms representing bulk flow and molecular diffusion are, respectively

a) (N_{A}+N_{B})C_{A}/C, D_{AB}dC_{A}/dz

b) (N_{A}+N_{B})C_{A}/C, D_{AB}dC_{A}/dz

c) (N_{A}+N_{B})C_{A}/C, (N_{A}+N_{B})C_{A}/C

d) (D_{AB}dC_{A}/dz, D_{AB}dC_{A}/dz)

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3. Consider loss of ethanol vapor by diffusion from a half-filled open test tube. At what point in the diffusion path will the contribution of the bulk flow term to the molar flux be maximum?

a) At the liquid-gas interface

b) In the bulk liquid

c) In the bulk gas

d) None of the mentioned

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4. A reaction 3A+2B+C=1.5D+E occurs in a reactor at steady state. What will be the value of the flux ratio N_{A}/N_{D}

(a)-2

(b)-0.5

(c) 2

(d)-0.5

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_{A}/N

_{D}= (rate of disappearance of A)/(rate of appearance of D) = -3/1.5 = -2.

5. For a component A of a mixture, concentration as a function of x is given:

C_{A}=5e^{-10x} (x is in cm and C_{A} in mol/liter)

Calculate the value of diffusion velocity (m/s)of the component A at the point x=0, if diffusivity of A in the mixture is 2.567*10^{-5}m^{2}/s.

a) 0.2567

b) 2.567

c) 0.0025

d) 3.541

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_{A}=(-)D

_{AB}*dC/dx C

_{A}(u

_{A}-U)= (-)D

_{AB}dC/dx…………1 Diffusion velocity= (u

_{A}-U)=(-D

_{AB}dC/dx)/C

_{A}dC/dx = -50e

^{-10x}C

_{A}= 5 mol/lit Put all the values in equation 1.

6. A sheet of Fe 1.0 mm thick is exposed to a oxidizing gas on one side and a deoxidizing gas on the other at 725°C. After reaching steady state, the Fe membrane is exposed to room temperature, and the C concentrations at each side of the membrane are 0.012 and 0.075 wt%. Calculate the diffusion coefficient (m^{2}/sec) if the diffusion flux is 1.4×10^{-8}kg/m^{2}-sec.

a) 9.87*10^{-12}

b) 9.87*10^{-13}

c) 9.87*10^{-11}

d) 9.87*10^{-10}

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^{3}. Concentration in kg/m

^{3}=[C

_{1}/(C

_{1}/ρ

_{1}+C2/ρ

_{2})]*1000 0.012% and 0.075% in kg/m

^{3}are 0.270 and 1.688 respectively. Putting all the values in the equation J

_{A}=(-)D

_{AB}dC/dx.

7. At which condition molar flux with respect to a stationary observer and with respect to a observer moving with molar average velocity?

a) In a very dilute solution

b) In a highly concentrated solution

c) At moderate concentration

d) Never

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_{A}= (N

_{A}+N

_{B})C

_{A}/C – D

_{AB}dC

_{A}/dz (general equation) (N

_{A}+N

_{B})C

_{A}/C =0 (in dilute solution) N

_{A}= -D

_{AB}dC

_{A}/dz = J

_{A}.

8. Which among the following is the statement of the ‘Fick’s Law’?

a) The molar flux of species relative to an observer moving with the molar average velocity is proportional to the concentration gradient of the species.

b) The mass flux of species relative to an observer moving with the molar average velocity is proportional to the concentration gradient of the species.

c) The molar flux of species relative to an observer moving with the mass average velocity is proportional to the concentration gradient of the species.

d) The molar flux of species relative to a stationary observer is proportional to the concentration gradient of the species.

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9. The gas A diffuses through non-diffusing B from point 1 to point 2. The total pressure is 2atm and y_{A1}=0.1 and y_{A2}=0.Then the ratio (dP_{A}/dz)1/(dP_{A}/dz)2 is

a) 10

b) 1.11

c) 0.9

d) 2.3

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10. In industries titanium is hardened through diffusion of carbon. The concentration of carbon at 1mm into the surface of the titanium slab is 0.25kg/m^{3} and at 3mm the concentration is 0.68kg/m^{3}. The rate at which the carbon is entering into its surface is 1.27*10-9kg/m^{2}.s. calculate the value of diffusion coefficient of carbon.

a) 5.91*10^{-12}

b) 5.91*10^{-10}

c) 5.91*10^{-11}

d) 5.91*10^{-13}

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^{4}1.27*10

^{-19}kg/m

^{2}.s= -D*(-215kg/m

^{4}) D=5.91*10

^{-12}m

^{2}/s.