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# Multiple choice question for engineering

## Set 1

1. What is the change in internal energy for a process which has final and initial states are exactly similar?
a) Positive
b) Negative
c) Zero
d) Cannot say

Answer: c [Reason:] Since internal energy is a state function, change in internal energy for the process will be zero.

2. What is the change in internal energy of 2 mole of air (Cv = 2.1 X 104 J/moleoC), if its temperature changes from 10oC to 20oC?
a) 420 kJ
b) 540 kJ
c) 840 kJ
d) 1050 kJ

Answer: a [Reason:] Change in internal energy = 2*(2.1 X 104)*(20 – 10) = 420 kJ.

3. What is the change in internal energy of 1 mole of air ((Cv = 2.1 X 104 J/moleoC), if its temperature changes from 10oC to 5oC?
a) 84 kJ
b) 105 kJ
c) – 84 kJ
d) – 105 kJ

Answer: d [Reason:] Change in internal energy = 1*(2.1 X 104)*(5 – 10) = – 105 kJ.

4. Ratio of change in internal energy of a substance from 4oC to T and from T to 10oC is 2, what is T?
a) 5oC
b) 6oC
c) 7oC
d) 8oC

Answer: d [Reason:] 2 = (T – 4)/(10 – T), => T = 8oC.

5. Ratio of change in internal energy of a substance from 15oC to T and from T to 10oC is – 2, what is T?
a) 5oC
b) 15oC
c) 20oC
d) 30oC

Answer: a [Reason:] – 2 = (T – 15)/(10 – T), => T = 5oC.

6. Total energy of the universe is always ______
a) Increasing
b) Decreasing
c) Constant
d) Cannot say

Answer: c [Reason:] According to the law of conservation of energy, total energy of the universe is always constant.

7. A stone has initial potential and kinetic energy as 10 J and 5 J respectively, if the final potential energy of the stone is 15 J what is its final kinetic energy?
a) 0
b) 5 J
c) 10 J
d) 15 J

Answer: a [Reason:] Law of conservation of energy, 10 + 5 = 15 + KE, => KE = 0.

8. A stone has initial potential and kinetic energy as 5 J and 20 J respectively, if the final kinetic energy of the stone is 15 J what is its final potential energy?
a) 0
b) 10 J
c) 15 J
d) 25 J

Answer: b [Reason:] 5 + 20 = 15 + PE, => PE = 10 J.

9. A stone has initial potential, kinetic and internal energy 4 J, 15 J and 20 J respectively, if the final kinetic energy and potential energy of the stone is 5 J and 10 J respectively, what is the final internal energy?
a) 15 J
b) 20 J
c) 24 J
d) 32 J

Answer: c [Reason:] Final internal energy = 4 + 15 + 20 – 5 – 10 = 24 J.

10. A stone has initial potential, kinetic and internal energy 7 J, 10 J and 2x J respectively, if the final kinetic energy, potential energy and internal energy are 5 J, 21 J and x respectively, what is the final internal energy?
a) 2 J
b) 4 J
c) 5 J
d) 9 J

Answer: d [Reason:] 7 + 10 + 2x = 5 + 21 + x, => x = 9 J.

## Set 2

1. Which of the following does the concept of material balance based upon?
a) Conservation of mass
b) Conservation of energy
c) Conservation of momentum
d) Conservation of Volume

Answer: a [Reason:] Material is simply conservation of mass.

2. The equation of material balance, (Final condition + Sum of outputs) is equal to which of the following?
a) Initial condition – Sum of inputs
b) Initial condition + Sum of inputs
c) Sum of inputs – Initial condition
d) None of the mentioned

Answer: b [Reason:] Equation of material balance is Final condition – Initial condition = Sum of inputs – Sum of outputs, => Final condition + Sum of outputs = Initial condition + Sum of inputs.

3. A container has 10 grams of water 5 grams of water is added and 2 grams of water is taken out, what is the final amount of water?
a) 7 grams
b) 10 grams
c) 13 grams
d) 15 grams

Answer: c [Reason:] Final condition = Initial condition + sum of inputs – sum of outputs = 10 + 5 – 2 = 13 grams.

4. 10 moles of O2 is added to 10 moles of H2, how many moles of H2O will it produce?
a) 5
b) 10
c) 15
d) 20

Answer: b [Reason:] Balanced equation is 2H2 + O2 -> 2H2O, => Moles of H2O = Moles of H2 = 10.

5. A combustion reaction has reactants 1 mole of CxHy and 2 moles of O2 and products 1 mole of CO2 and 2 mole of H2O, what is x + y?
a) 1
b) 3
c) 4
d) 5

Answer: d [Reason:] Moles of C, H and O in reactants = Moles of C, H and O in products, => C: 1*x = 1*1 => x = 1, H: 1*y = 2*2 => x + y = 5.

6. In a random reaction 2 mole of CH4 and 1 mole of C2H4 are reacted, and 1 mole of C3H8 and 1 mole of CxHy are produced, what is x*y?
a) 2
b) 4
c) 8
d) 12

Answer: b [Reason:] Material balance for C: 2*1 + 1*2 =1*3 +1*x, => x = 1, for H: 2*4 + 1*4 = 1*8 + 1*y, => y = 4, => x*y = 4.

7. A reaction has reactants 2 moles of NaOH and 1 mole of H2SO4, and products Na2SO4 and H2O, what are the total moles of products?
a) 1
b) 2
c) 3
d) 4

Answer: c [Reason:] Material Balance for Na: 2*1 = n1*2 => n1 = 1, for H: 2*1 + 1*2 = n2*2 => n2 = 2, => total moles of products = 1 + 2 = 3.

8. A reaction is A + 2B -> 3C, if 2 moles of A and 4 moles of B entered the system, what are the number of moles of C formed?
a) 2
b) 4
c) 6
d) 8

Answer: c [Reason:] Moles of C = 3*2 = 6.

9. 10 moles of A were present in a system initially, and 10 moles are added to it, it follows the reaction 4A -> B, what are number of moles of B produced?
a) 5
b) 10
c) 15
d) 20

Answer: a [Reason:] Moles of B = (10 + 10)/4 = 5.

10. 10 moles of A were present in a system initially, and 10 moles of C are added to it, it follows the reaction 2A + C -> 5B, what are number of moles of B produced?
a) 5
b) 10
c) 25
d) 50

Answer: c [Reason:] Mole of B = 5*5 = 25.

11. There were 10 moles of a substance present initially in a system, 5 moles were added to it and a reaction occurred so that its moles are reduced by 20%, what are the final moles of substance in the system?
a) 10
b) 12
c) 15
d) 18

Answer: b [Reason:] Final moles of substance = (10 + 5)*80/100 = 12.

12. There were 15 moles of a substance present initially in a system, 25 moles were added to it and a reaction occurred so that its moles are reduced by 50%, what are the final moles of substance in the system?
a) 10
b) 15
c) 20
d) 40

Answer: c [Reason:] Final moles of substance = (15 + 25)*50/100 = 20.

13. 10 moles of A were present in a system initially, and 12 moles of C are added to it, it undergoes the reaction 2A + 3C -> 2B, what are number of moles of B produced?
a) 4
b) 5
c) 8
d) 12

Answer: c [Reason:] Moles of B = 2*4 = 8.

14. 10 moles of A were present in a system initially, and 8 moles of C are added to it, it undergoes the reaction 5A + 3C -> 4B, what are number of moles of B produced?
a) 4
b) 6
c) 8
d) 10

Answer: c [Reason:] Moles of B = 4*2 = 8.

15. 8 moles of A were present in a system initially, and 24 moles of B are added to it, it undergoes the reaction 2A + 3B -> 4C + 5D, what are number of moles of D produced?
a) 10
b) 20
c) 30
d) 40

Answer: c [Reason:] Moles of D = 5*4 = 20.

## Set 3

1. What is the percentage of excess air, if 10 moles of air entered the process and only 5 moles of that are required?
a) 10%
b) 50%
c) 75%
d) 100%

Answer: d [Reason:] Percentage of excess air = 100*(10 – 5)/5 = 100%.

2. What is the percentage of excess air if 50 grams of air is in excess and 150 grams of air enters the process?
a) 10%
b) 25%
c) 50%
d) 100%

Answer: c [Reason:] Percentage of excess air = 100*50/(150 – 50) = 50%.

3. 10 moles of ethane is supplied with 49 moles of oxygen, what is the percentage of excess oxygen?
a) 20%
b) 40%
c) 50%
d) 70%

Answer: b [Reason:] The balanced reaction is C2H6 + 3.5O2 -> 2CO2 + 3H2O, => O2 required = 3.5*10 = 35 moles, => percentage of excess oxygen = 100*(49 – 35)/35 = 40%.

4. The extent of a reaction is 10, and the stoichiometric coefficient of O2 is 2.5, if the moles of O2 entering the process is 45, what is the percentage of excess air?
a) 20%
b) 40%
c) 60%
d) 80%

Answer: d [Reason:] Moles of O2 required = 10*2.5 = 25, => Percentage of excess air = 100*(45 – 25)/25 = 80%.

5. 144 grams of C5H12 is burnt with 64 grams O2, and 44 grams of CO2 is formed, what is the percentage of excess O2?
a) 25%
b) 50%
c) 75%
d) 100%

Answer: a [Reason:] The balanced chemical reaction is C5H12 + 2 -> 5CO2 + 6H2O, => Extent of reaction = (44/44 – 0)/5 = 0.2. Moles of O2 entered the process = 64/32 = 2, Moles of O2 required = 0.2*8 = 1.6, => Percentage of excess oxygen = 100*(2 – 1.6)/1.6 = 25%.

6. Ethene is burnt with 50% of excess air, what is the percentage of CO2 in the products?
a) 11.11%
b) 36.36%
c) 66.66%
d) 72.72%

Answer: b [Reason:] The reaction is C2H4 + 3O2 -> 2CO2 + 2H2O. Basis: 10 moles of C2H4, => moles of O2 reacted = 30, => moles of O2 entered the process = 45, => moles of CO2, H2O and O2 in products are 20, 20 and 15 respectively, => percentage of CO2 = 20/55*100 = 36.36%.

7. Ethene is burnt with 150% of excess air, what is the percentage of O2 in the products?
a) 12.5%
b) 33.3%
c) 45.4%
d) 52.9%

Answer: d [Reason:] The reaction is C2H4 + 3O2 -> 2CO2 + 2H2O. Basis: 10 moles of C2H4, => moles of O2 reacted = 30, => moles of O2 entered the process = 75, => moles of CO2, H2O and O2 in products are 20, 20 and 45 respectively, => percentage of O2 = 45/85*100 = 52.9%.

8. Pentane is burnt with 100% of excess air, what is the percentage of H2O in the products?
a) 12.4%
b) 34.6%
c) 42.1%
d) 56.9%

Answer: c [Reason:] The reaction is C5H12 + 2 -> 5CO2 + 6H2O. Basis: 10 moles of C5H12, => moles of O2 reacted = 80, => moles of O2 entered the process = 160, => moles of CO2, H2O and O2 in products are 50, 60 and 80, => percentage of H2O = 80/190*100 = 42.1%.

9. Propane is burnt with 20% excess O2, what is the percentage of CO2 in products?
a) 12.5%
b) 25%
c) 45%
d) 75.5%

Answer: a [Reason:] The reaction is C3H8 + 5O2 -> 3CO2 + 4H2O. Basis: 10 moles of C3H8, => moles of O2 reacted = 50, => moles of O2 entered the process = 60, => moles of CO2, H2O and O2 in products are 30, 40 and 10, => percentage of CO2 = 10/80*100 = 12.5%.

10. Octane is burnt with 40% excess O2, what is the percentage of CO2 in products?
a) 18.18%
b) 36.36%
c) 54.54%
d) 72.72%

Answer: b [Reason:] The reaction is C8H18 + 12.5O2 -> 8CO2 + 9H2O. Basis: 10 moles of C8H18, => moles of O2 reacted = 125, => moles of O2 entered the process = 175, => moles of CO2, H2O and O2 in products are 80, 90 and 50, => percentage of CO2 = 80/220*100 = 36.36%.

11. Methane is at the rate 50 moles is supplied to a reactor with air at the rate 1000 moles, the reactor leaves O2, N2, CO2 and H2O, what is the rate of products?
a) 900 moles
b) 950 moles
c) 1000 moles
d) 1050 moles

Answer: d [Reason:] The reaction is CH4 + 2O2 -> CO2 + 2H2O. O2 supplied = 1000*21/100 = 210 moles, N2 supplied = 1000*79/100 = 790 moles, => O2 unreacted = 210 – 100 = 110 moles, CO2 formed = 50 moles, H2O formed = 100 moles. => Rate of products = 790 + 110 + 50 + 100 = 1050 moles.

12. Methane is at the rate 50 moles is supplied to a reactor with air at the rate 1000 moles, the reactor leaves O2, N2, CO2 and H2O, what is the percentage of O2 in products?
a) 10.4%
b) 25.8%
c) 45.6%
d) 78.2%

Answer: a [Reason:] The reaction is CH4 + 2O2 -> CO2 + 2H2O. O2 supplied = 1000*21/100 = 210 moles, N2 supplied = 1000*79/100 = 790 moles, => O2 unreacted = 210 – 100 = 110 moles, CO2 formed = 50 moles, H2O formed = 100 moles. => Percentage of O2 = 110/1050*100 = 10.4%.

13. Methane is at the rate 50 moles is supplied to a reactor with air at the rate 1000 moles, the reactor leaves O2, N2, CO2 and H2O, what is the percentage of CO2 in products?
a) 4.7%
b) 10.4%
c) 16.5%
d) 24.3%

Answer: a [Reason:] The reaction is CH4 + 2O2 -> CO2 + 2H2O. O2 supplied = 1000*21/100 = 210 moles, N2 supplied = 1000*79/100 = 790 moles, => O2 unreacted = 210 – 100 = 110 moles, CO2 formed = 50 moles, H2O formed = 100 moles. => Percentage of CO2 = 50/1050*100 = 4.7%.

14. Methane is at the rate 50 moles is supplied to a reactor with air at the rate 1000 moles, the reactor leaves O2, N2, CO2 and H2O, what is the percentage of N2 in products?
a) 25.4%
b) 45.2%
c) 75.2%
d) 95.6%

Answer: c [Reason:] The reaction is CH4 + 2O2 -> CO2 + 2H2O. O2 supplied = 1000*21/100 = 210 moles, N2 supplied = 1000*79/100 = 790 moles, => O2 unreacted = 210 – 100 = 110 moles, CO2 formed = 50 moles, H2O formed = 100 moles. => Percentage of N2 = 790/1050*100 = 75.2%.

15. Methane is at the rate 50 moles is supplied to a reactor with air at the rate 1000 moles, the reactor leaves O2, N2, CO2 and H2O, what is the percentage of H2O in products?
a) 5.8%
b) 9.5%
c) 15.4%
d) 20.7%

Answer: b [Reason:] The reaction is CH4 + 2O2 -> CO2 + 2H2O. O2 supplied = 1000*21/100 = 210 moles, N2 supplied = 1000*79/100 = 790 moles, => Osub>2 unreacted = 210 – 100 = 110 moles, COsub>2 formed = 50 moles, Hsub>2O formed = 100 moles. => Percentage of H2O = 100/1050*100 = 9.5%.

## Set 4

1. What is the value of P in the following process?

a) 5 mole
b) 10 mole
c) 15 mole
d) 20 mole

Answer: c [Reason:] 10 + 20 = P + 10 + 5, => P = 15 mole.

2. What is the value of P in the following process?

a) 5 mole
b) 15 mole
c) 25 mole
d) 35 mole

Answer: c [Reason:] 10 + 20 = 5 + P, => P = 25 mole.

3. What is the value of P in the following process?

a) 5 mole
b) 10 mole
c) 15 mole
d) 20 mole

Answer: a [Reason:] 10 = P + 5, => P = 5 mole.

4. What is the value of F*P in the following process?

a) 25
b) 125
c) 150
d) 225

Answer: b [Reason:] F = 15 + 10 = 25 mole, P + 20 = F = 25, => P = 5 mole, => F*P = 125.

5. What is the value of H/P in the following process, if 2P + H = 16?

a) 1
b) 3
c) 6
d) 8

Answer: c [Reason:] P + 20 = H + 10, => H – P = 10, solving both equations, we get H = 12, P = 2, => H/P = 6.

Answer the following questions 6 – 10 for the diagram.

6. What is the value of B?
a) 100 Kg/hr
b) 200 Kg/hr
c) 300 Kg/hr
d) 400 Kg/hr

Answer: b [Reason:] Material balance for ethanol: 0.04*1000 = 0.2*B, => B = 200 Kg/hr.

7. What is the value of C?
a) 400 Kg/hr
b) 689.5 Kg/hr
c) 819.6 Kg/hr
d) 959.2 Kg/hr

Answer: d [Reason:] Material balance for air: 0.94*1000 = 0.98*C, => C = 959.2 Kg/hr.

8. What is the value of W?
a) 159.2 Kg/hr
b) 281.3 Kg/hr
c) 465.7 Kg/hr
d) 633.8 Kg/hr

Answer: a [Reason:] A + W = B + C, => 1000 + W = 200 + 959.2, => W = 159.2 Kg/hr.

9. What is the value of F?
a) 98.5 Kg/hr
b) 131.1 Kg/hr
c) 167.7 Kg/hr
d) 256.4 Kg/hr

Answer: c [Reason:] Material balance for ethanol: 200*0.2 = F*0.05 + D*0.98, => 5F + 98D = 4000, material balance for water: 200*0.8 = F*0.95 + D*0.02, => 95F + 2D = 16000, Solving both equations we get F = 167.7 Kg/hr.

10. What is the value of D?
a) 32.3 Kg/hr
b) 49.1 Kg/hr
c) 85.6 Kg/hr
d) 105.3 Kg/hr

Answer: a [Reason:] B = F + D, => 200 = 167.7 + D, => D = 32.3 Kg/hr.

11. How many independent equations are possible, if only one component exists in each stream?

a) 1
b) 2
c) 3
d) 4

Answer: b [Reason:] For whole process: 1 + 2 = 4 + 5, for first reactor: 1 + 2 = 3, for second reactor: 3 = 4 + 5, but if we equate second and third equation we get the first one, so there are 2 independent equations.

12. How many independent equations are possible, if two components are involved in each of streams?

a) 1
b) 2
c) 3
d) 4

Answer: d [Reason:] It will be just the double of the number of independent equations if there was only one component.

13. 1 has pure A and 2 has pure B and 3, 4 and 5 has mixture of A and B, how many independent equations are possible?

a) 1
b) 2
c) 3
d) 4

Answer: d [Reason:] It will be just twice the number when there is only one component.

14. How many independent equations are possible if each stream contains mixture of A, B and C?

a) 1
b) 3
c) 6
d) 8

Answer: c [Reason:] It will be just thrice the number when there was only one component.

15. How many independent equation are possible if 1 has pure A, 2 has mixture of B and C, 3 has mixture of A, B and C, 4 has pure C, 5 has mixture of A and B.

a) 1
b) 3
c) 6
d) 9

Answer: c [Reason:] It will be just thrice the number when there was only one component.

## Set 5

1. What is the pressure if 10 N of force is acting normally on 5 m2 surface area?
a) 2 Pa
b) 4 Pa
c) 8 Pa
d) 10 Pa

Answer: a [Reason:] Pressure = 10/5 = 2Pa.

2. What is the pressure if 10 N of force acts at 60 degrees from the normal of a 5 m2 surface?
a) 0.5 Pa
b) 1 Pa
c) 2 Pa
d) 4 Pa

Answer: b [Reason:] Normal component of the force = 10cos60o = 10*0.5 = 5 N, => Pressure = 5/5 = 1 Pa.

3. What is the pressure if 10 N of force acts at 30 degrees from the surface of area 5 m2?
a) 1 Pa
b) 2 Pa
c) 5 Pa
d) 10 Pa

Answer: a [Reason:] Normal component of the force = 10sin30o = 10*0.5 = 5 N, => Pressure = 5/5 = 1 Pa.

4. What is the pressure of 1 mole of an ideal gas at 27oC occupying 1 Liter of volume?
a) 12.31 atm
b) 24.63 atm
c) 36.95 atm
d) 48.94 atm

Answer: b [Reason:] For ideal gas PV = nRT, => P = 1*0.0821*300/1 = 24.63 atm.

5. An open tank 10 m deep is completely filled with a liquid of density 5 kg/m3, what is the pressure difference at the top and bottom?
a) 100 N/m2
b) 250 N/m2
c) 500 N/m2
d) 1000 N/m2

Answer: c [Reason:] Pressure difference = dgh = 5*10*10 = 500 N/m2.

6. 10 mm of water (density = 1000 kg/m3) and 5 mm of a liquid has the same pressure drop, what is the density of liquid?
a) 500 kg/m3
b) 1000 kg/m3
c) 1500 kg/m3
d) 2000 kg/m3

Answer: d [Reason:] pressure of water = pressure of liquid, => d1h1 = d2h2, => 10*1000 = 5*d2, => d = 2000 kg/m3.

7. Which of the following is not a pressure measuring device?
a) Manometer
b) Barometer
c) Galvanometer
d) None of the mentioned

Answer: c [Reason:] Galvanometer is used to measure current.

8. Bernoulli’s Equation is the conservation of?
a) Energy
b) Momentum
c) Pressure
d) Mass

Answer: a [Reason:] Bernoulli’s equation is modified form of conservation of energy equation.

9. What is the pressure difference of the ends of a U-tube manometer filled with liquid (density = 10 kg/m3) the difference in the height of the liquid in the tubes is 5 cm?
a) 5 N/m2
b) 10 N/m2
c) 15 N/m2
d) 20 N/m2

Answer: a [Reason:] Pressure difference = dgh = 10*10*0.05 = 5 N/m2.

10. A hydraulic lever has input surface area 2 m2, and output surface area 10 m2, if the input force is 5 N, then what is the output force?
a) 1 N
b) 2 N
c) 5 N
d) 10 N

Answer: a [Reason:] Hydraulic lever works on the Pascal’s principle, => F1A1 = F2A2, => 5*2 = F2*10, => F2 = 1 N.

11. A Closed U-tube manometer has a gas at one end and vacuum at other end, if the height difference of the liquid (density = 10 kg/m3) in the manometer in 5 cm, what is the pressure of the gas?
a) 10 N/m2
b) 5 N/m2
c) 2.5 N/m2
d) 1 N/m2

Answer: b [Reason:] Pressure of the gas = dgh = 10*10*0.05 = 5 N/m2.

12. Archimedes’ principle describes which of the following quantities?
a) Pressure
b) Buoyancy
c) Velocity
d) Mass

Answer: b [Reason:] Archimedes’ principle states that buoyant force on a body is equal to the weight of the body.

13. An object is dipped in water, if the weight of the object measured by spring balance is 10 g and buoyancy force acting on the object is 0.1 N then what is the actual mass of the object?
a) 10 g
b) 20 g
c) 30 g
d) 40 g

Answer: b [Reason:] Weight of the object = (10*103)*10 + 0.1 = 0.2 N, => actual mass of the object = 0.2/10 = 0.02 kg = 20 g.

14. An open end manometer is filled with a gas on one end and other end is open to atmosphere with height difference of liquid (density = 10000 Kg/m3) 10 cm, what is the pressure of gas?
a) 1 atm
b) 1.1 atm
c) 1.2 atm
d) 1.3 atm