# Thermodynamics MCQ Questions & Answers

Thermodynamics MCQs : This section focuses on the "Thermodynamics". These Multiple Choice Questions (MCQs) should be practiced to improve the Thermodynamics skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

A sealed rigid vessel has volume of 1 m3 and contains 2 kg of water at 100°C. The vessel is now heated. If a safety pressure valve is installed, at what pressure should the valve be set to have a maximum temperature of 200°C ?

A. 431.3 kPa
B. 531.3 kPa
C. 631.3 kPa
D. 731.3 kPa

Question 2

The entropy __________ in an irreversible cyclic process.

A. remains constant
B. decreases
C. increases

Question 3

Which of the following has the minimum atomic mass?

A. Oxygen
B. Sulphur
C. Nitrogen
D. Carbon

Question 4

What is the cathodic and anodic reactions respectively of Cu-Ag system?

A. Ag==>Ag+2+2e and Cu+2+2e==>Cu
B. Cu==>Cu+2+2e and Ag==>Ag+2+2e
C. 2Ag+1+2e==>2Ag and Cu==>Cu+2+2e
D. 2Ag==>2Ag+1+2e and Cu+2+2e==>Cu

Question 5

According to Gay-Lussac law for a perfect gas, p/T = constant, if v is kept constant.

A. TRUE
B. FALSE

Question 6

Which of the following statement is incorrect?

A. The liquid fuels consist of hydrocarbons.
B. The liquid fuels have higher calorific value than solid fuels.
C. The solid fuels have higher calorific value than liquid fuels.
D. A good fuel should have low ignition point.

Question 7

A piston-cylinder device initially contains air at 150 kPa and 27°C. At this state, the volume is 400 litre. The mass of the piston is such that a 350 kPa pressure is required to move it. The air is now heated until its volume has doubled. Determine work done by the air.

A. 120 kJ
B. 130 kJ
C. 100 kJ
D. 140 kJ

Question 8

Which of the following diagrams shows the stability of metals over a range of pH and potential of a system?

A. Phase diagrams
B. Pourbaix diagrams
C. Phase diagrams and Pourbaix diagrams
D. Colling curves

Question 9

Which is not a state variable/function in the given options according to thermodynamics?

A. Temperature
B. Enthalpy
C. Functions dependent on path
D. Internal energy

Question 10

The equation of the second law of thermodynamics says that____

A. Total change in entropy is always zero
B. We cannot find entropy for an irreversible process
C. Entropy change is defined as the heat added in an irreversible process
D. Entropy is a state process

Question 11

When cut-off ratio is __________ the efficiency of Diesel cycle approaches to Otto cycle efficiency.

A. zero
B. 01-May
C. 04-May
D. 1

Question 12

The kinetic energy of molecules of a gas becomes zero at absolute zero temperature.

A. Agree
B. Disagree

Question 13

Workdone in a free expansion process is

A. zero
B. minimum
C. maximum
D. positive

Question 14

Which is the process in which no heat exchange is there between system and surroundings and in which no dissipative phenomena occur?

B. Reversible process
C. Isentropic process
D. Work

Question 15

The compression ratio for petrol engines is

A. 3 to 6
B. 5 to 8
C. 15 to 20
D. 20 to 30

Question 16

A cycle consisting of one constant pressure, one constant volume and two isentropic processes is known as

A. Carnot cycle
B. Stirling cycle
C. Otto cycle
D. Diesel cycle

Question 17

The first law of thermodynamics is proved by experiments. Select the correct choice for it.

A. de is an exact differential
B. dq is an exact differential
C. dw is an exact differential
D. The relation has been proved theoretically

Question 18

The specific heat of water is

A. 1.817
B. 2512
C. 4.187
D. none of these

Question 19

Which of the following is correct?

A. Absolute pressure = Gauge pressure + Atmospheric pressure
B. Gauge pressure = Absolute pressure + Atmospheric pressure
C. Atmospheric pressure = Absolute pressure + Gauge pressure
D. Absolute pressure = Gauge pressure - Atmospheric pressure

Question 20

Which of the following is a cathode and anode respectively in the Ag-Fe system?

A. Iron (Fe) and Silver (Ag)
B. Silver (Ag) and Iron (Fe)
C. Gold (Ag) and Iron (Fe)
D. Iron (Fe) and Gold (Ag)

Question 21

Which of the following is/are the applications of modern electrode kinetic principles?

A. Anodic protection
B. Noble metal alloying
C. Methods to measure corrosion rates rapidly
D. Anodic protection, noble metal alloying and methods to measure corrosion rates rapidly

Question 22

Which of the following is/are the limitations of Pourbaix diagrams?

A. Rate of reaction is can’t be predicted
B. It neglects the impurities of working conditions
C. Stability of metallic species is predicted
D. Rate of reaction is not predicted and it neglects the impurities of working conditions

Question 23

First law when expressed in terms of entropy takes the form_____

A. T ds = de – p dv
B. T ds = dh – p dv
C. T ds = de + p dv
D. T ds = dh + p dv

Question 24

The efficiency of Stirling cycle is __________ Carnot cycle.

A. greater than
B. less than
C. equal to

Question 25

The absolute zero temperature is taken as

A. -273°C
B. 273°C
C. 237°F
D. -237°F

Question 26

An isothermal process is governed by

A. Boyle's law
B. Charles' law
C. Gay-Lussac law

Question 27

One kg of carbon requires 4/3 kg of oxygen and produces __________ kg of carbon monoxide gas.

A. 08-Mar
B. 11-Mar
C. 11-Jul
D. 07-Mar

Question 28

The sum of internal energy (U) and the product of pressure and volume (p.v) is known as

A. workdone
B. entropy
C. enthalpy
D. none of these

Question 29

One kg of carbon monoxide requires __________ kg of oxygen to produce 11/7 kg of carbon dioxide gas.

A. All
B. 04-Jul
C. 11-Apr
D. 09-Jul

Question 30

An adiabatic process is one in which

A. no heat enters or leaves the gas
B. the temperature of the gas changes
C. the change in internal energy is equal to the mechanical workdone
D. all of the above

Question 31

The atomic mass of oxygen is

A. 12
B. 14
C. 16
D. 32

Question 32

Which of the following is the lightest and most volatile liquid fuel?

A. Gasoline
B. Kerosene
C. Fuel oil

Question 33

When the gas is heated at constant volume, the heat supplied increases the internal energy of the gas.

A. TRUE
B. FALSE

Question 34

When coal is strongly heated continuously for 42 to 48 hours in the absence of air in a closed vessel, the process is known as __________ of fuel.

A. atomisation
B. carbonisation

Question 35

The processes occuring in open system which permit the transfer of mass to and from the system, are known as

A. flow processes
B. non-flow processes
D. none of these

Question 36

There is a loss of heat in an irreversible process.

A. TRUE
B. FALSE

Question 37

The value of 1 mm of Hg is equal to

A. 1.333 N/m2
B. 13.33 N/m2
C. 133.3 N/m2
D. 1333 N/m2

Question 38

All the commercial liquid fuels are derived from natural petroleum (or crude oil).

A. TRUE
B. FALSE

Question 39

Find the change in u for carbon dioxide between 600 K and 1200 K for a constant Cv0 value.

A. 291.8 kJ/kg
B. 391.8 kJ/kg
C. 491.8 kJ/kg
D. 591.8 kJ/kg

Question 40

A series of operations, which takes place in a certain order and restore the initial conditions at the end, is known as

A. reversible cycle
B. irreversible cycle
C. thermodynamic cycle
D. none of these

Question 41

Specific heat for gas is almost constant in the case of_______

A. Space vehicle
B. High-temperature flow
C. Air in a desert
D. Chemically reacting flow at high- speeds

Question 42

For a block of ice on a plate, second law of thermodynamics says that____

A. The plate will get hotter
B. Ice will get cooler
C. Cannot give conclusive direction
D. Ice will melt

Question 43

The distillation carried out in such a way that the liquid with the lowest boiling point is first evaporated and recondensed, then the liquid with the next higher boiling point is then evaporated and recondensed, and so on until all the available liquid fuels are separately recovered in the sequence of their boiling points. Such a process is called

A. cracking
B. carbonisation
C. fractional distillation
D. full distillation

Question 44

Carbonisation of coal consists of

A. drying and crushing the coal to a fine powder
B. moulding the finely ground coal under pressure with or without a binding material
C. heating the wood with a limited supply of air to temperature not less than 280°C
D. none of the above

Question 45

There is no change in internal energy in an isothermal process.

A. Correct
B. Incorrect

Question 46

Why is controlled oxidation needed?

A. High energy
B. Loss of products
C. Temperature
D. All of the mentioned

Question 47

Gas laws are applicable to

A. Gases as well as vapours
B. Gases alone and not to vapors
C. Gases and steam
D. Gases and vapours under certain conditions

Question 48

Water gas is obtained by passing air and a large amount of steam over waste coal at about 650°C.

A. Correct
B. Incorrect

Question 49

Which of the following gas is mostly used in town for street and domestic lighting and heating?

A. Producer gas
B. Coal gas
C. Mond gas
D. Coke oven gas

Question 50

Which of the following is/are the applications of Pourbaix diagrams?

A. Predicting the spontaneous direction of reactions
B. To reduce corrosion attack
C. To reduce corrosion attack, to predict the direction of spontaneous reaction and to estimate the composition of corrosion product
D. To estimate the composition of corrosion product

Question 51

The value of gas constant (R) in S. I. units is

A. 0.287 J/kgK
B. 2.87 J/kgK
C. 28.7 J/kgK
D. 287 J/kgK

Question 52

An isentropic process is restrictive and is not feasible in real life.

A. False
B. True

Question 53

The constant pressure, constant volume and constant pvn processes are regarded as irreversible process.

A. TRUE
B. FALSE

Question 54

Stirling and Ericsson cycles are

A. reversible cycles
B. irreversible cycles
C. semi-reversible cycles
D. quasi-static cycles

Question 55

The amount of heat required to raise the temperature of the unit mass of gas through one degree at constant volume, is called

A. specific heat at constant volume
B. specific heat at constant pressure
C. kilo Joule
D. none of these

Question 56

Identify the incorrect source for the corresponding variables of the first law.

B. Squeezing of volume: dw
C. Heating: de
D. Displacement of system boundary: dq

Question 57

Which is the correct result according to the second law of thermodynamics?

A. Total change in entropy is always zero
B. Total change in entropy in a reversible process is always zero
C. Total change in entropy in an irreversible process is always zero
D. Total change in entropy for an irreversible process is negative

Question 58

The ratio of specific heat at constant pressure (cp) and specific heat at constant volume (cv) is

A. equal to one
B. less than one
C. greater than one
D. none of these

Question 59

A piston/cylinder with a cross-sectional area of 0.01 m^2 is resting on the stops. With an outside pressure of 100 kPa, what should be the water pressure to lift the piston?

A. 178kPa
B. 188kPa
C. 198kPa
D. 208kPa

Question 60

The efficiency of Diesel cycle approaches to Otto cycle efficiency when

A. cut-off is increased
B. cut-off is decreased
C. cut-off is zero
D. cut-off is constant

Question 61

Flow over a rocket outside the boundary layer is isentropic.

A. False
B. True

Question 62

An electrochemical reaction is always a combination of oxidation half-cell and a reduction of half-cell.

A. TRUE
B. FALSE

Question 63

For a calorically perfect gas, entropy is not________

A. State function
B. Conserved in a reversible process
C. A function of two thermodynamic variables
D. Zero always

Question 64

The equation of state for a perfect gas is p = δRT, where R is______ (for air at standard conditions).

A. 287 kJ/kg.K
B. 8314 kJ/kg
C. 8.314 kJ/kgK
D. 287 J/kg.K

Question 65

The pressure exerted by an ideal gas is __________ of the kinetic energy of all the molecules contained in a unit volume of gas.

A. one-half
B. one-third
C. two-third
D. three-fourth

Question 66

A large exhaust fan in a lab room keeps the pressure inside at 10 cm water relative vacuum to the hallway? What is the net force acting on the door measuring 1.9 m by 1.1 m?

A. 2020 N
B. 2030 N
C. 2040 N
D. 2050 N

Question 67

In the first law of thermodynamics, the total energy of the system remains constant.

A. TRUE
B. FALSE

Question 68

Which is the wrong result for a calorically perfect gas?

A. e=cvT
B. h=cpT
C. cp and cp are functions of T
D. For T < 1000 K, specific heats are constant

Question 69

One kg of diatomic Oxygen is present in a 500 L tank. Find the specific volume on both mass and mole basis.

A. 0.6 m3/kg , 0.260 m3/mole
B. 0.5 m3/kg , 0.0160 m3/mole
C. 0.56 m3/kg , 0.0215 m3/mole
D. 0.7 m3/kg , 0.0325 m3/mole

Question 70

The behaviour of a perfect gas, undergoing any change in the variables which control physical properties, is governed by

A. Boyle's law
B. Charles' law
C. Gay-Lussac law
D. all of these

Question 71

The value of specific heat at constant pressure (cp) is __________ that of at constant volume (cv).

A. less than
B. equal to
C. more than

Question 72

The efficiency and work ratio of a simple gas turbine cycle are

A. low
B. very low
C. high
D. very high

Question 73

The efficiency of Diesel cycle increases with

A. decrease in cut-off
B. increase in cut-off
C. constant cut-off
D. none of these

Question 74

The universal gas constant of a gas is the product of molecular mass of the gas and the gas constant.

A. Correct
B. Incorrect

Question 75

Calculate the change in enthalpy of carbon dioxide from 30 to 1500°C at 100 kPa at constant specific heat.

A. 2237.7 kJ/kg
B. 1637.7 kJ/kg
C. 1237.7 kJ/kg
D. 2337.7 kJ/kg

Question 76

If the value of n = 0 in the equation pvn = C, then the process is called

A. constant volume process
C. constant pressure process
D. isothermal process

Question 77

Coal gas is obtained by mixing coal and gas at ambient conditions.

A. Yes
B. No

Question 78

According to Avogadro's law, the density of any two gases is __________ their molecular masses, if the gases are at the same temperature and pressure.

A. equal to
B. directly proportional to
C. inversely proportional to

Question 79

A 5m^3 container is filled with 840 kg of granite (density is 2400 kg/m^3) and the rest of the volume is air (density is 1.15 kg/m^3). Find the mass of air present in the container.

A. 9.3475 kg
B. 8.3475 kg
C. 6.3475 kg
D. 5.3475 kg