Chemical Engineering Thermodynamics
Exam (2025-2026) | Questions &
Answers (Graded A)
A refrigerator may be termed as a - ANSWER - heat pump
For a stable phase at constant pressure and temperature, the fugacity of each
component in a binary system __________ as its mole fraction increases. - ANSWER -
increases
Which of the following is not an intensive property? - ANSWER - Heat capacity
Out of the following refrigration cycles, which one has the minimum COP (Co-efficient of
performance)? - ANSWER - Air cycle
Measurement of thermodynamic property of temperature is facilitated by __________
law of thermodynamics. - ANSWER - zeroth
The theoretical minimum work required to separate one mole of a liquid mixture at 1
atm, containing 50 mole % each of n- heptane and n- octane into pure compounds each
at 1 atm is... - ANSWER - -RT ln 0.5
Keeping the pressure constant, to double the volume of a given mass of an ideal gas at
27°C, the temperature should be raised to __________ °C. - ANSWER - 327
Entropy of an ideal gas depends upon its - ANSWER - Pressure and Temperature
Isobaric process means a constant process. - ANSWER - pressure
No work is done by the system, when a reaction occurs at constant - ANSWER -
volume
If the vapour pressure at two temperatures of a solid phase in equilibrium with its liquid
phase are known, then the latent heat of fusion can be calculated by the - ANSWER -
Clayperon-Claussius equation
The freezing point of a liquid decreases when the pressure is increased, if the liquid
__________ while freezing. - ANSWER - contracts
"At the absolute zero temperature, the entropy of every perfectly crystalline substance
becomes zero". This follows from the - ANSWER - third law of thermodynamics
,During Joule-Thomson expansion of gases - ANSWER - enthalpy remains constant.
The accentric factor of a materical, 'ω', is defined as ω = -log10(Prsat)Tr-1 = 0.7, where,
Prsat = reduced vapor pressure, Tr = reduced temperature. The value of accentric
factor is always - ANSWER - < 1
Degrees of freedom at triple point will be - ANSWER – 0
Maximum work that could be secured by expanding the gas over a given pressure
range is the__________work. - ANSWER - isothermal
Internal energy change of a system over one complete cycle in a cyclic process is -
ANSWER - zero
Heating of water under atmospheric pressure is an __________ process. - ANSWER -
isobaric
Van Laar equation deals with the activity co-efficients in - ANSWER - binary solutions
High __________ is an undesirable property for a good refrigerant. - ANSWER -
viscosity
Solubility of a substance which dissolves with an increase in volume and liberation of
heat will be favoured by the - ANSWER - low pressure and low temperature.
Entropy is a measure of the __________ of a system. - ANSWER - disorder
A chemical reaction will occur spontaneously at constant pressure and temperature, if
the free energy is - ANSWER - negative
Fundamental principle of refrigeration is based on the __________ law of
thermodynamics. - ANSWER - second
For a spontaneous process, free energy - ANSWER - decreases whereas the entropy
increases
A refrigeration cycle is a reversed heat engine. Which of the following has the maximum
value of the co-efficient of performance (COP) for a given refrigeration effect? -
ANSWER - Carnot refrigeration cycle.
In a working refrigerator, the value of COP is always - ANSWER - >1
__________ increases with increase in pressure. - ANSWER - The melting point of
wax; The boiling point of a liquid
,"Law of corresponding states" says that - ANSWER - two different gases behave
similarly, if their reduced properties (i.e. P, V and T) are same.
Linde gas liquefaction process employs cooling - ANSWER - by throttling
Pick out the wrong statement pertaining to the decomposition of PCl5 represented by,
PCl5 PCl3 + Cl2.Degree of dissociation of PCl5 will - ANSWER - None of these -
decrease on addition of Cl2.; increase on addition of an inert gas at constant pressure;
decrease on increasing the pressure of the system.
Joule-Thomson experiment is - ANSWER - adiabatic and isenthalpic
Boyle's law for gases states that - ANSWER - P∞1/V,when temperature & mass of the
gas remain constant.
1st law of thermodynamics is nothing but the law of conservation of - ANSWER - energy
In a reversible chemical reaction (where, Δx = number of moles of products-number of
moles of reactants) - ANSWER - addition of inert gas favours the forward reaction,
when Δx is positive; pressure has no effect on equilibrium, when Δn = 0; addition of
inert gas has no effect on the equilibrium constant at constant volume for any value of
Δx (+ ve, - ve) or zero).
Out of the following refrigeration cycles, which one has maximum COP? - ANSWER -
Carnot cycle
Pick out the correct statement: - ANSWER - Under reversible conditions, the adiabatic
work is less than isothermal work.
In any spontaneous process, - ANSWER - both F and A decreases
Which of the following is a thermodynamic property of a system? - ANSWER - Entropy
Equilibrium constant decreases as the temperature - ANSWER - increases, for an
exothermic reaction.
The expression G=nRT . ln P2/P1,gives the free energy change - ANSWER - with
pressure changes at constant temperature.
All gases during throttling process at atmospheric temperature and pressure show a
cooling effect except - ANSWER - H2
Compressibility factor for almost all the gases are approximately same at the same -
ANSWER - reduced pressure and reduced temperature.
, Pick out the wrong statement. - ANSWER - The fugacity co-efficient is zero for an ideal
gas.
The co-efficient of performance (COP) of a refrigerating system, which is its index of
performance, is defined as the ratio of useful refrigeration to the net work. The units of
__________ and COP are the same. - ANSWER - None of these - kinematic viscosity;
work; temperature
The chemical potential of a component (μi) of a phase is the amount by which its
capacity for doing all work, barring work of expansion is increased per unit amount of
sustance added for an infinitesimal addition at constant temperature and pressure. It is
given by - ANSWER - All of these (refer to the image)
In jet refrigerators, the refrigerating fluid is practically always - ANSWER - water
Water on heating from 1 to 4°C - ANSWER - contracts
Pick out the correct statement. - ANSWER - Efficiency of an Otto engine is higher than
that of a diesel engine for the same compression ratio.
When pressure is applied on the system, icewater, then - ANSWER - more water will be
formed.
Partial molar free energy of an element A in solution is same as its - ANSWER -
chemical potential
Free energy change at equilibrium is - ANSWER - zero
Heat pump - ANSWER - accomplishes both a and b - space heating in winter; space
cooling in summer
The temperature at which both liquid and gas phases are identical, is called the
__________ point. - ANSWER - critical
What is the value of ln y (where y = activity co-efficient) for ideal gases? - ANSWER -
zero
A closed system is cooled reversibly from 100°C to 50°C. If no work is done on the
system - ANSWER - U and S both decreases
Which is not a refrigerant? - ANSWER - C2H4Cl2
The partial pressure of each constituent present in an alloy is __________ the total
vapor pressure exerted by the alloy. - ANSWER - less than
Exam (2025-2026) | Questions &
Answers (Graded A)
A refrigerator may be termed as a - ANSWER - heat pump
For a stable phase at constant pressure and temperature, the fugacity of each
component in a binary system __________ as its mole fraction increases. - ANSWER -
increases
Which of the following is not an intensive property? - ANSWER - Heat capacity
Out of the following refrigration cycles, which one has the minimum COP (Co-efficient of
performance)? - ANSWER - Air cycle
Measurement of thermodynamic property of temperature is facilitated by __________
law of thermodynamics. - ANSWER - zeroth
The theoretical minimum work required to separate one mole of a liquid mixture at 1
atm, containing 50 mole % each of n- heptane and n- octane into pure compounds each
at 1 atm is... - ANSWER - -RT ln 0.5
Keeping the pressure constant, to double the volume of a given mass of an ideal gas at
27°C, the temperature should be raised to __________ °C. - ANSWER - 327
Entropy of an ideal gas depends upon its - ANSWER - Pressure and Temperature
Isobaric process means a constant process. - ANSWER - pressure
No work is done by the system, when a reaction occurs at constant - ANSWER -
volume
If the vapour pressure at two temperatures of a solid phase in equilibrium with its liquid
phase are known, then the latent heat of fusion can be calculated by the - ANSWER -
Clayperon-Claussius equation
The freezing point of a liquid decreases when the pressure is increased, if the liquid
__________ while freezing. - ANSWER - contracts
"At the absolute zero temperature, the entropy of every perfectly crystalline substance
becomes zero". This follows from the - ANSWER - third law of thermodynamics
,During Joule-Thomson expansion of gases - ANSWER - enthalpy remains constant.
The accentric factor of a materical, 'ω', is defined as ω = -log10(Prsat)Tr-1 = 0.7, where,
Prsat = reduced vapor pressure, Tr = reduced temperature. The value of accentric
factor is always - ANSWER - < 1
Degrees of freedom at triple point will be - ANSWER – 0
Maximum work that could be secured by expanding the gas over a given pressure
range is the__________work. - ANSWER - isothermal
Internal energy change of a system over one complete cycle in a cyclic process is -
ANSWER - zero
Heating of water under atmospheric pressure is an __________ process. - ANSWER -
isobaric
Van Laar equation deals with the activity co-efficients in - ANSWER - binary solutions
High __________ is an undesirable property for a good refrigerant. - ANSWER -
viscosity
Solubility of a substance which dissolves with an increase in volume and liberation of
heat will be favoured by the - ANSWER - low pressure and low temperature.
Entropy is a measure of the __________ of a system. - ANSWER - disorder
A chemical reaction will occur spontaneously at constant pressure and temperature, if
the free energy is - ANSWER - negative
Fundamental principle of refrigeration is based on the __________ law of
thermodynamics. - ANSWER - second
For a spontaneous process, free energy - ANSWER - decreases whereas the entropy
increases
A refrigeration cycle is a reversed heat engine. Which of the following has the maximum
value of the co-efficient of performance (COP) for a given refrigeration effect? -
ANSWER - Carnot refrigeration cycle.
In a working refrigerator, the value of COP is always - ANSWER - >1
__________ increases with increase in pressure. - ANSWER - The melting point of
wax; The boiling point of a liquid
,"Law of corresponding states" says that - ANSWER - two different gases behave
similarly, if their reduced properties (i.e. P, V and T) are same.
Linde gas liquefaction process employs cooling - ANSWER - by throttling
Pick out the wrong statement pertaining to the decomposition of PCl5 represented by,
PCl5 PCl3 + Cl2.Degree of dissociation of PCl5 will - ANSWER - None of these -
decrease on addition of Cl2.; increase on addition of an inert gas at constant pressure;
decrease on increasing the pressure of the system.
Joule-Thomson experiment is - ANSWER - adiabatic and isenthalpic
Boyle's law for gases states that - ANSWER - P∞1/V,when temperature & mass of the
gas remain constant.
1st law of thermodynamics is nothing but the law of conservation of - ANSWER - energy
In a reversible chemical reaction (where, Δx = number of moles of products-number of
moles of reactants) - ANSWER - addition of inert gas favours the forward reaction,
when Δx is positive; pressure has no effect on equilibrium, when Δn = 0; addition of
inert gas has no effect on the equilibrium constant at constant volume for any value of
Δx (+ ve, - ve) or zero).
Out of the following refrigeration cycles, which one has maximum COP? - ANSWER -
Carnot cycle
Pick out the correct statement: - ANSWER - Under reversible conditions, the adiabatic
work is less than isothermal work.
In any spontaneous process, - ANSWER - both F and A decreases
Which of the following is a thermodynamic property of a system? - ANSWER - Entropy
Equilibrium constant decreases as the temperature - ANSWER - increases, for an
exothermic reaction.
The expression G=nRT . ln P2/P1,gives the free energy change - ANSWER - with
pressure changes at constant temperature.
All gases during throttling process at atmospheric temperature and pressure show a
cooling effect except - ANSWER - H2
Compressibility factor for almost all the gases are approximately same at the same -
ANSWER - reduced pressure and reduced temperature.
, Pick out the wrong statement. - ANSWER - The fugacity co-efficient is zero for an ideal
gas.
The co-efficient of performance (COP) of a refrigerating system, which is its index of
performance, is defined as the ratio of useful refrigeration to the net work. The units of
__________ and COP are the same. - ANSWER - None of these - kinematic viscosity;
work; temperature
The chemical potential of a component (μi) of a phase is the amount by which its
capacity for doing all work, barring work of expansion is increased per unit amount of
sustance added for an infinitesimal addition at constant temperature and pressure. It is
given by - ANSWER - All of these (refer to the image)
In jet refrigerators, the refrigerating fluid is practically always - ANSWER - water
Water on heating from 1 to 4°C - ANSWER - contracts
Pick out the correct statement. - ANSWER - Efficiency of an Otto engine is higher than
that of a diesel engine for the same compression ratio.
When pressure is applied on the system, icewater, then - ANSWER - more water will be
formed.
Partial molar free energy of an element A in solution is same as its - ANSWER -
chemical potential
Free energy change at equilibrium is - ANSWER - zero
Heat pump - ANSWER - accomplishes both a and b - space heating in winter; space
cooling in summer
The temperature at which both liquid and gas phases are identical, is called the
__________ point. - ANSWER - critical
What is the value of ln y (where y = activity co-efficient) for ideal gases? - ANSWER -
zero
A closed system is cooled reversibly from 100°C to 50°C. If no work is done on the
system - ANSWER - U and S both decreases
Which is not a refrigerant? - ANSWER - C2H4Cl2
The partial pressure of each constituent present in an alloy is __________ the total
vapor pressure exerted by the alloy. - ANSWER - less than
