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Multiple choice question for engineering

Set 1

1. Energy out and Energy in of a system are 10 J and 25 J respectively, what is the efficiency of the system?
a) 10%
b) 40%
c) 50%
d) 80%

View Answer

Answer: b [Reason:] Efficiency = 10/25*100 = 40%.

2. Energy out and Energy in of a system are 5 J and 25 J respectively, what is the efficiency of the system?
a) 20%
b) 40%
c) 60%
d) 80%

View Answer

Answer: a [Reason:] Efficiency = 5/25*100 = 20%.

3. Energy out and Energy in of a system are 10 J and 20 J respectively, what is the efficiency of the system?
a) 20%
b) 30%
c) 40%
d) 50%

View Answer

Answer: d [Reason:] Efficiency = 10/20*100 = 50%.

4. Energy out and Energy in of a system are 40 J and 25 J respectively, what is the efficiency of the system?
a) 40%
b) 80%
c) 160%
d) 200%

View Answer

Answer: c [Reason:] Efficiency = 40/25*100 = 160%.

5. Energy out and Energy in of a system are 15 J and 25 J respectively, what is the efficiency of the system?
a) 40%
b) 60%
c) 80%
d) 110%

View Answer

Answer: b [Reason:] Efficiency = 15/25*100 = 60%.

6. What is the efficiency of the system, if the actual work output from the process is 10 J and work output for a reversible process is 40 J?
a) 10%
b) 25%
c) 40%
d) 65%

View Answer

Answer: b [Reason:] Efficiency = 10/40*100 = 25%.

7. What is the efficiency of the system, if the actual work output from the process is 20 J and work output for a reversible process is 25 J?
a) 10%
b) 20%
c) 40%
d) 80%

View Answer

Answer: d [Reason:] Efficiency = 20/25*100 = 80%.

8. What is the efficiency of the system, if the actual work output from the process is 15 J and work output for a reversible process is 20 J?
a) 25%
b) 50%
c) 75%
d) 100%

View Answer

Answer: c [Reason:] Efficiency = 15/20*100 = 75%.

9. What is the efficiency of the system, if the actual work input from the process is 10 J and work input for a reversible process is 20 J?
a) 20%
b) 50%
c) 100%
d) 200%

View Answer

Answer: d [Reason:] Efficiency = 20/10*100 = 200%.

10. What is the efficiency of the system, if the actual work input from the process is 20 J and work input for a reversible process is 25 J?
a) 20%
b) 80%
c) 125%
d) 150%

View Answer

Answer: c [Reason:] Efficiency = 25/20*100 = 125%.

11. What is the efficiency of a heat engine with heat input 10 J and work output 7 J?
a) 30%
b) 70%
c) 100%
d) 140%

View Answer

Answer: b [Reason:] Efficiency = 7/10*100 = 70%.

12. What is the efficiency of a heat engine with heat input 20 J and work output 5 J?
a) 25%
b) 50%
c) 75%
d) 100%

View Answer

Answer: a [Reason:] Efficiency = 5/20*100 = 25%.

13. What is the efficiency of a heat engine with heat input 5 J and work output 8 J?
a) 40%
b) 80%
c) 160%
d) 200%

View Answer

Answer: c [Reason:] Efficiency = 5/8*100 = 160%.

14. What is the coefficient of performance of a system, if its work input is 50 J and heat removed is 35 J?
a) 35%
b) 50%
c) 70%
d) 95%

View Answer

Answer: c [Reason:] Coefficient of performance = 35/50*100 = 70%.

15. What is the coefficient of performance of a system, if its work input is 75 J and heat removed is 45 J?
a) 20%
b) 40%
c) 60%
d) 80%

View Answer

Answer: c [Reason:] Coefficient of performance = 45/75*100 = 60%.

Set 2

1. A reactor supplied with CO2 and H2O, the product contains 10% H2CO3 and 90% H2O, what is the feed rate of CO2, if the rate of product is 50 mole?
a) 5 mole
b) 10 mole
c) 25 mole
d) 50 mole

View Answer

Answer: a [Reason:] The reaction is CO2 + H2O -> H2CO3. Let the rates of CO2 and H2O be F and W respectively. Element balances, C: F(1) = 0.1P(1), => 10F = P, => F = 5 mole.

2. A reactor supplied with CO2 and H2O, the product contains H2O and H2CO3, if the rate of CO2 is 10 mole, what is the percentage of H2CO3 in products?
a) 10
b) 50
c) 75
d) 100

View Answer

Answer: d [Reason:] The reaction is CO2 + H2O -> H2CO3. Let the rate of CO2 and H2O and product be F and W respectively, and the fraction of H2CO3 in products be x. Element balances, C: F(1) = x*10(1), => F = 10x, => x = 1, => percentage of H2CO3 = 100%.

3. A reactor supplied with CO2 and H2O, the product contains H2O and H2CO3, if the rate of H2O is 10 mole, what is the rate of products?
a) 5 mole
b) 10 mole
c) 15 mole
d) 20 mole

View Answer

Answer: b [Reason:] The reaction is CO2 + H2O -> H2CO3. Let the rate of products be P, and the fraction of H2CO3 in products be x, material balances, H: 10(2) = x*P(2) + (1 – x)*P(2), => P = 10 mole.

4. A reactor supplied with CO2 and H2O, the product contains CO2, H2O and H2CO3, if the rate of products is 10 mole and percentage of CO2 in products is 20%, what is the feed rate of H2O?
a) 2 mole
b) 4 mole
c) 8 mole
d) 10 mole

View Answer

Answer: c [Reason:] The reaction is CO2 + H2O -> H2CO3. Let the rate of H2O be W, and percentage of H2O in products be x. Material balances, H: W(2) = x*10(2) + (1 – x – 0.2)*10(2), => W = 8 mole.

5. A reactor supplied with CO2 and H2O, the product contains 40% CO2, 30% H2O and 30% H2CO3, what is the ratio of feed rate of CO2 and rate of products?
a) 0.3
b) 0.4
c) 0.7
d) 0.9

View Answer

Answer: c [Reason:] The reaction is CO2 + H2O -> H2CO3. Let the rate of CO2, H2O and H2CO3 be F, W and P respectively. Element balances, C: F(1) = 0.4P(1) + 0.3P(1), => F/P = 0.7.

6. A reactor is supplied with Hexane and hydrogen to produce 20% methane, 30% propane and 50% butane, what is the ratio of hydrogen consumed and the hexane reacted?
a) 0.21
b) 0.45
c) 0.59
d) 0.73

View Answer

Answer: d [Reason:] The reaction is 2C6H14 + 2H2 -> CH4 + 2C3H8 + C5H12, Let the rate of Hexane, hydrogen and products be F, W and P respectively. Element balances, C: 2F(6) = 0.2P(1) + 2*0.3P(3) + 0.5P(5), => 8F = 3P, H: 2F(14) + 2W(2) = 0.2P(4) + 2*0.3P(8) + 0.5P(12), => 7F + W = 2.9P, => W/F= 2.2/3 = 0.73.

7. A reactor is supplied with 10 mole of Hexane and some hydrogen to produce 20% methane, 30% propane and 50% butane, what is the rate of products?
a) 10 mole
b) 16.6 mole
c) 26.6 mole
d) 40 mole

View Answer

Answer: c [Reason:] The reaction is 2C6H14 + 2H2 -> CH4 + 2C3H8 + C5H12, Let the rate of products be P. Element balance, C: 2*10(6) = 0.2P(1) + 2*0.3P(3) + 0.5P(5), => 120 = 4.5P, => P = 26.6 mole.

8. A reactor is supplied with glucose and oxygen to produce 40% CO2, 60% H2O, what is the ratio of glucose reacted and products?
a) 0.2
b) 0.4
c) 0.6
d) 0.8

View Answer

Answer: b [Reason:] The reaction is C6H12O6 + 6O2 -> 6CO2 + 6H2O, Let the rate of glucose and products be F and P, Element balances, C: F(6) = 6*0.4P(1), => F/P = 0.4.

9. A reactor is supplied with 10 moles glucose and excess oxygen to produce 40% CO2, 60% H2O, what is the rate of products?
a) 25 mole
b) 50 mole
c) 75 mole
d) 100 mole

View Answer

Answer: a [Reason:] The reaction is C6H12O6 + 6O2 -> 6CO2 + 6H2O, Let the rate of products be P. Element balances, C: 10(6) = 6*0.4P(1), => P = 25 mole.

10. A reactor is supplied with 10 moles glucose and excess oxygen to produce CO2 and H2O, if the rate of products is 25 moles, what is the percentage of CO2 in the products?
a) 0.1
b) 0.2
c) 0.3
d) 0.4

View Answer

Answer: d [Reason:] The reaction is C6H12O6 + 6O2 -> 6CO2 + 6H2O. Let the fraction of CO2 be x, Element balances, C: 10(6) = 6*x*5(1), => x = 0.4.

11. Ethane is supplied at the rate F with oxygen at the rate W and leaves the following products CO2, H2O, O2, C2H6 and H2 at the rate P. How many independent element balances are possible?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: c [Reason:] The reaction is C2H6 + 3.5O2 -> 2CO2 + 3H2O, since there are three elements C, H and O, we can write 3 independent material balances.

12. Ethane is supplied with chlorine in a reactor, how many independent element balances can you write?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: c [Reason:] The reaction is C2H6 + Cl2 -> C2H5Cl + HCl, Element balance C: 2F = 2xP, H: 6F = 5xP + (1 – x)P, Cl: 2W = xP + (1 – x)P, => The equations are F = xP, 6F = 4xP + P, and 2W = P, which are independent.

13. A reactor is supplied with 2 streams both at same rates, one has pure Cl2, and another has pure C2H6, if the product has 20% C2H5Cl and 80% HCl, what is the ratio of rate of feed and rate of product?
a) 0.2
b) 0.5
c) 2
d) 5

View Answer

Answer: a [Reason:] The reaction is C2H6 + Cl2 -> C2H5Cl + HCl, Let the rate of feed and products be F and P respectively. Element balances, C: F(2) = 0.2P(2), => F/P = 0.2.

14. A reactor is supplied with 2 streams both at same rates, one has pure Cl2, and another has pure C2H6, if the product has 20% C2H5Cl and 50% HCl and 30% C2H6, what is the ratio of rate of feed and rate of product?
a) 0.2
b) 0.5
c) 2
d) 5

View Answer

Answer: b [Reason:] The reaction is C2H6 + Cl2 -> C2H5Cl + HCl, Let the rate of feed and products be F and P respectively. Element balances, C: F(2) – 0.3P(2) = 0.2P(2), => F/P = 0.5.

15. A reactor is supplied with 2 streams both at the rate 5 mole, one has 40% Cl2 and 60% N2, and another has pure C2H6, if the product has C2H5Cl, HCl and N2 at the rate 20 mole, what is the percentage of HCl in products?
a) 10%
b) 15%
c) 25%
d) 30%

View Answer

Answer: b [Reason:] The reaction is C2H6 + Cl2 -> C2H5Cl + HCl, Let the fraction of C2H5Cl, HCl and N2 be x, y and (1 – x – y) respectively. Element balances, Cl: 0.4*5(2) = x*10(1) + y*10(1), => x + y = 0.4, C: 5(2) = x*20(2), => x = 0.25, => y = 0.4 – 0.25 = 0.15, => percentage of HCl = 15%.

Set 3

1. What separates system and surroundings?
a) Boundary
b) Temperature
c) Pressure
d) None of the mentioned

View Answer

Answer: a [Reason:] Boundary separates system and surroundings.

2. Which of the following is true for open system?
a) Flow system
b) Non flow system
c) Cannot say
d) None of the mentioned

View Answer

Answer: a [Reason:] Since matter can come in or out in an open system, it is a flow system.

3. Which of the following is true about closed system?
a) Flow system
b) Non flow system
c) Cannot say
d) None of the mentioned

View Answer

Answer: b [Reason:] Since matter cannot come in or out in a closed system, it is a non-flow system.

4. Which of the following does not change in steady state system?
a) Flow in rate
b) Flow out rate
c) Accumulation
d) None of the mentioned

View Answer

Answer: c [Reason:] In a steady state system accumulation is zero.

5. Which of the following is correct about an isothermal process?
a) ∆T = 0
b) dT = 0
c) ∆T /= 0
d) None of the mentioned

View Answer

Answer: b [Reason:] In an isothermal process, temperature does not changes throughout the process, => dT = 0.

6. Which of the following is a state function?
a) Work
b) Entropy
c) Heat
d) None of the mentioned

View Answer

Answer: b [Reason:] Entropy is a state function as it does not depend on the path of the process.

7. Which of the following is a path function?
a) Work
b) Internal Energy
c) Entropy
d) None of the mentioned

View Answer

Answer: a [Reason:] Since work depends on the path of a process, it is a path function.

8. Internal energy is which of the following function?
a) Path function
b) State function
c) Cannot say
d) None of the mentioned

View Answer

Answer: b [Reason:] Since internal energy does not depend on path, it is a state function.

9. Which of the following has steepest P-V curve?
a) Adiabatic
b) Isothermal
c) Isobaric
d) None of the mentioned

View Answer

Answer: a [Reason:] Slope of adiabatic curve is greater than that of isothermal and isobaric, so it has the steepest P-V curve.

10. What we call a process having constant volume throughout?
a) Isobaric
b) Isochoric
c) Isothermal
d) Adiabatic

View Answer

Answer: b [Reason:] Isochoric process has constant volume throughout.

11. Which of the following is an extensive variable?
a) Pressure
b) Temperature
c) Volume
d) None of the mentioned

View Answer

Answer: c [Reason:] Volume is dependent on mass, it is extensive variable.

12. Which of the following is an extensive variable?
a) Energy
b) Volume
c) Moles
d) All of the mentioned

View Answer

Answer: d [Reason:] Energy, Volume and Moles all are dependent on mass, all are extensive variable.

13. Which of the following is an intensive variable?
a) Moles
b) Enthalpy per mole
c) Enthalpy
d) All of the mentioned

View Answer

Answer: b [Reason:] Enthalpy and mole both are extensive properties, since the ratio of two extensive properties is an intensive property, Enthalpy per mole is an extensive property.

14. Which of the following is an intensive property?
a) Mole
b) Gibbs Free energy
c) Enthalpy
d) None of the mentioned

View Answer

Answer: d [Reason:] Since all depends on mass, all are extensive properties.

15. Which of the following is an intensive property?
a) Refractive index
b) Hardness
c) Density
d) All of the mentioned

View Answer

Answer: d [Reason:] Since none of the properties depends on mass, all are intensive properties.

Set 4

1. Which of the following is not the type of energy?
a) Enthalpy
b) Heat
c) Entropy
d) Work

View Answer

Answer: c [Reason:] Entropy in not a type of energy.

2. Which of the following process P-V work in highest?
a) Second derivative is negative
b) Second derivative is positive
c) Second derivative is zero
d) All of the mentioned

View Answer

Answer: a [Reason:] Work in highest when area under the P-V curve is highest, which is when second derivative of the curve is negative.

3. An object is moved from one position to another with a specific force, what type of work is it?
a) Shaft Work
b) Flow Work
c) Mechanical Work
d) None of the mentioned

View Answer

Answer: c [Reason:] Since work is caused by mechanical force it is a mechanical work.

4. An object is moved at a distance of 10 m with the force of 5 N, what is the work done by the force?
a) 5 Joule
b) 50 Joule
c) 500 Joule
d) 5000 Joule

View Answer

Answer: b [Reason:] Work = 10*5 = 50 N-m = 50 Joule.

5. An object moved forward 10 meters and then comes back 5 meter all with a constant force of 5 N, what is the work done by the force?
a) 5 Joule
b) 25 Joule
c) 50 Joule
d) 75 Joule

View Answer

Answer: b [Reason:] Work = (10 – 5)* 5 = 25 Joule.

6. A piston cylinder is compressed with some pressure, what is the work done on the system?
a) Positive
b) Negative
c) Zero
d) Cannot say

View Answer

Answer: a [Reason:] Since pressure and displacement are positive their products are also positive, => work done on the system is positive.

7. A piston cylinder expands with some pressure, what is the work done by the system?
a) Positive
b) Negative
c) Zero
d) Cannot Say

View Answer

Answer: a [Reason:] Since direction of displacement and force are same, work done will be positive.

8. A piston cylinder contracts from 10 Liter to 5 Liter with and external pressure of 10 Pa, what is the work done on the system?
a) 0.5 mJ
b) 5 mJ
c) 10 mJ
d) 50 mJ

View Answer

Answer: d [Reason:] Work = 10*(10 – 5) = 50 mJ.

9. A piston cylinder expands from 7 liter to 15 liter with external pressure of 500 Pa, what is the work done by the system?
a) – 1.5 Joule
b) – 4 Joule
c) 1.5 Joule
d) 4 Joule

View Answer

Answer: b [Reason:] Work = 500*(15 – 7) = 4000 mJ = 4 Joule.

10. A piston cylinder expands from 8 liter to 12 liter with external pressure of 900 Pa, what is the work done on the system?
a) 3.6 Joule
b) – 3.6 Joule
c) 7.2 Joule
d) – 7.2 Joule

View Answer

Answer: b [Reason:] Work done on the system = 900(8 – 12) = – 3600 mJ = – 3.6 J.

11. You shake a thermos so that the temperature of tea inside increases by 2oC, if you transferred Q amount of heat to the thermos, which of the following satisfies Q?
a) Q > 0
b) Q < 0
c) Q = 0
d) Cannot say

View Answer

Answer: c [Reason:] If you are shaking a thermos, you are doing work on it not transferring any heat.

12. Q amount of heat is transferred in an adiabatic process, which of the following is correct?
a) Q > 0
b) Q = 0
c) Q < 0
d) Cannot say

View Answer

Answer: b [Reason:] In an adiabatic process Q = 0.

13. Q amount of heat is transferred to a system, which of the following is correct?
a) Q > 0
b) Q < 0
c) Q = 0
d) Cannot say

View Answer

Answer: a [Reason:] Since heat is transferred to a system, => Q > 0.

14. Temperature of a system is increased with no change in internal energy, if the work done by the system is 10 Joule, what amount of heat is taken out from the system?
a) 10 J
b) – 10 J
c) 0
d) 5 J

View Answer

Answer: b [Reason:] W = – 10, => 0 = Q + W, => Q = 10 J, => amount of heat taken out = – 10 J.

15. Ratio heat transferred from 37oC to a colder body and from that body to – 11oC is 2, what is the temperature of colder body if surface areas are same for all bodies?
a) – 5oC
b) – 3oC
c) 5oC
d) 9oC

View Answer

Answer: c [Reason:] 2 = (37 – T)/(T + 11), => T = 5oC.

Set 5

1. For an open unsteady state system, 5 J of heat was supplied and 10 J of work was done on the system, what is the value of change in enthalpy?
a) 5 J
b) 10 J
c) 15 J
d) 20 J

View Answer

Answer: c [Reason:] ∆H = 5 + 10 = 15 J.

2. For an open unsteady state system, 10 J of heat was supplied and 10 J of work was done by the system, what is the value of change in enthalpy?
a) 0
b) 10 J
c) 20 J
d) – 20 J

View Answer

Answer: a [Reason:] ∆H = 10 – 10 = 0.

3. For an open unsteady state system, 5 J of heat was supplied and 10 J of work was done by the system, what is the value of change in enthalpy?
a) – 5 J
b) 5 J
c) 10 J
d) 15 J

View Answer

Answer: a [Reason:] ∆H = 5 – 10 = – 5 J.

4. For an open unsteady state system, 15 J of heat was taken off and 10 J of work was done by the system, what is the value of change in enthalpy?
a) – 5 J
b) 5 J
c) 25 J
d) – 25 J

View Answer

Answer: a [Reason:] ∆H = 10 – 15 = – 5 J.

5. For an open unsteady state system, 15 J of heat was supplied and -5 J of work was done on the system, what is the value of change in enthalpy?
a) 10 J
b) – 15 J
c) 20 J
d) – 25 J

View Answer

Answer: a [Reason:] ∆H = 15 – 5 = 10 J.

6. Which of the following represents vaporization?
a) Change of vapor to liquid
b) Change of vapor to solid
c) Change of solid to vapor
d) Change of liquid to vapor

View Answer

Answer: d [Reason:] Vaporization is the reverse of condensation which is change of liquid to vapor.

7. Which of the following can definitely cause vaporization?
a) Heating a liquid
b) Heating a liquid at constant pressure
c) Cooling a liquid
d) Cooling a liquid at constant volume

View Answer

Answer: b [Reason:] Vaporization is caused by heating a liquid at constant pressure.

8. Vaporization starts at which point?
a) Dew point
b) Bubble point
c) Triple point
d) None of the mentioned

View Answer

Answer: b [Reason:] Bubble point is the point at which liquid starts evaporating which is the point at which vaporization starts.

9. What is the vaporization temperature of water at standard conditions?
a) 100oF
b) 212oF
c) 345oF
d) 432oF

View Answer

Answer: b [Reason:] Vaporization temperature of water at standard conditions is 100oC = 212oF.

10. What is the point of saturation of a condensable vapor?
a) Bubble point
b) Boiling point
c) Triple point
d) Dew point

View Answer

Answer: d [Reason:] Condensation of gas starts at its dew point.