ChE Thermodynamics Flashcards
Maximum work that could be secured by expanding the gas over a given pressure range is the __________ work.
isothermal
adiabatic
isentropic
none of these
isothermal
W = PΔV
Internal energy change of a system over one complete cycle in a cyclic process is ____.
zero
+ve
-ve
dependent on the path
zero
Heating of water under atmospheric pressure is an __________ process.
isochoric
isobaric
adiabatic
isothermal
isobaric
Van Laar equation deals with the activity co-efficients in
binary solutions
ternary solutions
azeotropic mixture only
none of these
binary solutions
High __________ is an undesirable property for a good refrigerant.
specific heat
latent heat of vaporisation
viscosity
specific vapor volume
viscosity
Solubility of a substance which dissolves with an increase in volume and liberation of heat will be favoured by the _____.
low pressure and high temperature.
low pressure and low temperature.
high pressure and low temperature.
high pressure and high temperature.
low pressure and low temperature.
Entropy is a measure of the __________ of a system.
disorder
orderly behaviour
temperature changes only
none of these
disorder
A chemical reaction will occur spontaneously at constant pressure and temperature, if the free energy is
zero
positive
negative
none of these
negative
Fundamental principle of refrigeration is based on the __________ law of thermodynamics.
zeroth
first
second
third
second
The second law of thermodynamics states that heat cannot spontaneously flow from a cold body to a hot body.
For a spontaneous process, free energy
is zero
increases
decreases whereas the entropy increases
and entropy both decrease
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 ?
Vapor compression cycle using expansion valve.
Air refrigeration cycle.
Vapor compression cycle using expansion engine.
Carnot refrigeration cycle.
Carnot refrigeration cycle.
In a working refrigerator, the value of COP is always
0
< 0
< 1
> 1
> 1
COP = Qc/W. The work removed from the cold reservoir is always greater than the work required to operate the ref.
_________ increases with increase in pressure.
The melting point of wax
The boiling point of a liquid
both (a) and (b)
neither (a) nor (b)
both (a) and (b)
A refrigerator may be termed as a
heat pump
heat engine
Carnot engine
none of these
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.
decreases
increases
remains same
decreases linearly
increases
Which of the following is not an intensive property ?
Chemical potential
Surface tension
Heat capacity
None of these
Heat capacity
Dependent on mass as unit is J/g*°C. The intensive property is the specific heat capacity.
Out of the following refrigration cycles, which one has the minimum COP (Co-efficient of performance)?
Air cycle
Carnot cycle
Ordinary vapour compression cycle
Vapour compression with a reversible expansion engine
Air cycle
↑COP ↑efficiency:
Air cycle < ordinary vapor < vapor compression < carnot
Measurement of thermodynamic property of temperature is facilitated by __________ law of thermodynamics.
1st
zeroth
3rd
none of these
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
-2 RT ln 0.5
-RT ln 0.5
0.5 RT
2 RT
-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.
270
327
300
540
327
Entropy of an ideal gas depends upon its
pressure
temperature
both (a) & (b)
neither (a) nor (b)
both (a) & (b)
Isobaric process means a constant process.
temperature
pressure
volume
entropy
pressure
No work is done by the system, when a reaction occurs at constant
volume
temperature
pressure
none of these
volume
W = PΔV
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
Maxwell’s equation
Clayperon-Claussius equation
Van Laar equation
Nernst Heat Theorem
Clayperon-Claussius equation
The freezing point of a liquid decreases when the pressure is increased, if the liquid __________ while freezing.
contracts
expands
does not change in volume
either (a), (b) or (c)
contracts
“At the absolute zero temperature, the entropy of every perfectly crystalline substance becomes zero”. This follows from the _____.
third law of thermodynamics
second law of thermodynamics
Nernst heat theorem
Maxwell’s relations
third law of thermodynamics
During Joule-Thomson expansion of gases
enthalpy remains constant.
entropy remains constant.
temperature remains constant.
none of these.
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
> 2
< 1
> 1
< 3
< 1
Degress of freedom at triple point will be
0
1
2
3
0
df = 2 - P + C
df = 2 - 3 + 1
“Law of corresponding states” says that:
, two different gases behave similarly, if their reduced properties (i.e. P, V and T) are same.
the surface of separation (i. e. the meniscus) between liquid and vapour phase disappears at the critical temperature.
no gas can be liquified above the critical temperature, howsoever high the pressure may be.
the molar heat of energy of gas at constant volume should be nearly constant (about 3 calories).
, two different gases behave similarly, if their reduced properties (i.e. P, V and T) are same.
Linde gas liquefaction process employs cooling
by throttling
by expansion in an engine
at constant pressure
none of these
by throttling
Pick out the wrong statement pertaining to the decomposition of PCl5 represented by, PCl5 PCl3 + Cl2.Degree of dissociation of PCl5 will _____.
decrease on addition of Cl2.
increase on addition of an inert gas at constant pressure.
decrease on increasing the pressure of the system.
none of these
none of these
Boyle’s law for gases states that _____.
P ⍺ 1/V, when temperature is constant.
P ⍺ 1/V, when temperature & mass of the gas remain constant.
P ⍺ V, at constant temperature & mass of the gas.
P/V = constant, for any gas.
P ⍺ 1/V, when temperature & mass of the gas remain constant.
1st law of thermodynamics is nothing but the law of conservation of
momentum
mass
energy
none of these
energy
In a reversible chemical reaction (where, Δx = number of moles of products-number of moles of reactants )
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).
all ‘a’, ‘b’ & ‘c’.
all ‘a’, ‘b’ & ‘c’.
Out of the following refrigeration cycles, which one has maximum COP ?
Air cycle
Carnot cycle
Ordinary vapor compression cycle
Vapor compression with a reversible expansion engine
Carnot cycle
↑COP ↑efficiency:
Air cycle < ordinary vapor < vapor compression < carnot
Pick out the correct statement:
In an isothermal system, irreversible work is more than reversible work.
Under reversible conditions, the adiabatic work is less than isothermal work.
Heat, work, enthalpy and entropy are all ‘state functions’.
Matter and energy can not be exchanged with the surroundings in a closed system.
Under reversible conditions, the adiabatic work is less than isothermal work.
In any spontaneous process,
only F decreases
only A decreases
both F and A decreases
both F and A increase
both F and A decreases
ΔG = ΔF - TΔS
ΔG = ΔA - PΔV
Which of the following is a thermodynamic property of a system ?
Concentration
Mass
Temperature
Entropy
Entropy
Equilibrium constant decreases as the temperature
increases, for an exothermic reaction.
decreases, for an exothermic reaction.
increases, for an endothermic reaction.
none of these.
increases, for an exothermic reaction.
The expression, ΔG = nRTln(P2/P1) , gives the free energy change:
with pressure changes at constant temperature.
under reversible isothermal volume change.
during heating of an ideal gas.
during cooling of an ideal gas.
with pressure changes at constant temperature.
All gases during throttling process at atmospheric temperature and pressure show a cooling effect except
CO2
H2
O2
N2
H2
Compressibility factor for almost all the gases are approximately same at the same
pressure and temperature.
reduced pressure and reduced temperature.
critical pressure and critical temperature.
none of these.
reduced pressure and reduced temperature.
Pick out the wrong statement.
Activity co-efficient is dimensionless.
In case of an ideal gas, the fagacity is equal to its pressure.
In a mixture of ideal gases, the fugacity of a component is equal to the partial pressure of the component.
The fugacity co-efficient is zero for an ideal gas.
The fugacity co-efficient is zero for an ideal gas.
It should be 1.
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.
kinematic viscosity
work
temperature
none of these
none of these
In jet refrigerators, the refrigerating fluid is practically always
water
ammonia
freon
brine
water
Water on heating from 1 to 4°C
contracts
expands
has same volume
may contract or expand
contracts
Pick out the correct statement.
Compression ratio of an Otto engine is comparatively higher than a diesel engine.
Efficiency of an Otto engine is higher than that of a diesel engine for the same compression ratio.
Otto engine efficiency decreases with the rise in compression ratio, due to decrease in work produced per quantity of heat.
Diesel engine normally operates at lower compression ratio than an Otto engine for an equal output of work.
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
equilibrium can not be established.
more ice will be formed.
more water will be formed.
evaporation of water will take place.
more water will be formed.
Partial molar free energy of an element A in solution is same as its
chemical potential
activity
fugacity
activity co-efficient
activity
Free energy change at equilibrium is
zero
positive
negative
indeterminate
zero
Heat pump
accomplishes only space heating in winter.
accomplishes only space cooling in summer.
accomplishes both (a) and (b).
works on Carnot cycle.
accomplishes both (a) and (b).
The temperature at which both liquid and gas phases are identical, is called the __________ point.
critical
triple
freezing
boiling
critical
What is the value of ln y (where y = activity co-efficient) for ideal gases ?
Zero
Unity
Infinity
Negative
Zero
A closed system is cooled reversibly from 100°C to 50°C. If no work is done on the system
its internal energy (U) decreases and its entropy (S) increases.
U and S both decreases
U decreases but S is constant.
U is constant but S decreases.
U and S both decreases
Which is not a refrigerant ?
SO2
NH3
CCl2F2
C2H4Cl2
C2H4Cl2
not used anymore due to ozone depleting ability
The partial pressure of each constituent present in an alloy is __________ the total vapor pressure exerted by the alloy.
less than
equal to
more than
either (b) or (c); depends on the type of alloy
less than
Entropy change of mixing two liquid substances depends upon the
molar concentration
quantity (i.e. number of moles)
both (a) and (b)
neither (a) nor (b)
both (a) and (b)
The four properties of a system viz. P, V, T, S are related by __________ equation.
Gibbs-Duhem
Gibbs-Helmholtz
Maxwell’s
none of these
Maxwell’s
If the pressure on 100 c.c. of air is halved, then its volume (at the same temperature) would be __________ c.c.
100
50
205
200
200
Pick out the wrong statement.
Cp of monoatomic gases such as metallic vapor is about 5 kcal/kg.atom.
The heat capacity of solid inorganic substance is exactly equal to the heat capacity of the substance in the molten state.
There is an increase in entropy, when a spontaneous change occurs in an isolated system.
At absolute zero temperature, the heat capacity for many pure crystalline substances is zero.
The heat capacity of solid inorganic substance is exactly equal to the heat capacity of the substance in the molten state.
Heat capacity is affected by the state of the substance. Ex: c_h2o and c_ice is different.
The principle applied in liquefaction of gases is
adiabatic expansion.
Joule-Thomson effect.
both (a) and (b).
neither (a) nor (b).
both (a) and (b).
Co-efficient of performance for a reversed Carnot cycle working between temperatures T1 and T2 (T1 > T2) is ____.
T2/T1-T2
T1/T1-T2
T1-T2/T1
T1-T2/T2
T2/T1-T2
The number of degrees of freedom for an azeotropic mixture in a two component vapour-liquid equilibria is/are
zero
one
two
three
one
df = 2 - P + C - a
df = 2 - 2 + 2 - 1
Any substance above its critical temperature exists as
saturated vapour
solid
gas
liquid
gas
Which of the following decreases with increase in pressure ?
Melting point of ice
Melting point of wax
Boiling point of liquids
none of these
Melting point of ice
Isentropic process means a constant __________ process.
enthalpy
pressure
entropy .
none of these
entropy
1/V (𝛅V/𝛅T)_P is the mathematical expression of ____.
Joule-Thomson co-efficient.
specific heat at constant pressure (Cp).
co-efficient of thermal expansion.
specific heat at constant volume (CV).
co-efficient of thermal expansion.
In case of steady flow compression polytropic process (PVn = constant), the work done on air is the lowest, when
n = y = 1.4
n = 0
n = 1
n = 1.66
n = 1
A liquid under pressure greater than its vapour pressure for the temperature involved is called a __________ liquid.
subcooled
saturated
non-solidifiable
none of these
subcooled
For a real gas, the chemical potential is given by
RT dlnP
RT dlnf
R dlnf
none of these
RT dlnf
At absolute zero temperature, all substances have the same
heat capacity
crystalline structure
entropy
none of these
heat capacity
Lowering of condenser temperature (keeping the evaporator temperature constant) in case of vapour compression refrigeration system results in
increased COP.
same COP.
decreased COP.
increased or decreased COP ; depending upon the type of refrigerant.
increased COP.
Pick out the correct statement.
If an insoluble gas is passed through a volatile liquid placed in a perfectly insulated container, the temperature of the liquid will increase.
A process is irreversible as long as Δ S for the system is greater than zero.
The mechanical work done by a system is always equal to P.dV.
The heat of formation of a compound is defined as the heat of reaction leading to the formation of the compound from its reactants.
The heat of formation of a compound is defined as the heat of reaction leading to the formation of the compound from its reactants.
Grams of butane (C4H10) formed by the liquefaction of 448 litres of the gas (measured at (STP) would be
580
640
1160
data insufficient; can’t be computed
1160
The thermodynamic law, PVy = constant, is not applicable in case of
ideal compression of air.
free expansion of an ideal gas.
adiabatic expansion of steam in a turbine.
adiabatic compression of a perfect gas.
free expansion of an ideal gas.
Mollier diagram is a plot of
temperature vs. enthalpy
temperature vs. enthalpy
entropy vs. enthalpy
temperature vs. internal energy
entropy vs. enthalpy
(𝛅E/𝛅T)_V is the mathematical expression for:
CV
enthalpy change
free energy change
none of these
none of these
The activity of an ideal gas is numerically __________ its pressure.
more than
less than
equal to
data insufficient, can’t be predicted
equal to
Specific heat of a gas for a reversible adiabatic process is
negative
zero
infinity
none of these
zero
When a gas in a vessel expands, its internal energy decreases. The process involved is
reversible
irreversible
isothermal
adiabatic
reversible
A system is said to be isopiestic, if there is no __________ change.
temperature
pressure
volume
none of these
pressure
In a turbine, the fluid expands almost
isothermally
isobarically
adiabatically
none of these
adiabatically
The unity of Planck’s constant ‘h’ in the equation, E = hv is
J/s
J.S
J/kmol
kmol/J
J.S
Specific/molar Gibbs free energy for a pure substance does not change during
sublimation
vaporisation
melting
either (a), (b) or (c)
either (a), (b) or (c)
Refrigeration capacity of a household refrigerator may be round about __________ tons.
0.15
1.5
4.5
6.5
0.15
(𝛅H/𝛅T)_P is the mathematical expression for
CV
entropy change
Gibbs free energy
none of these
none of these
In polytropic process (PVn = constant), if n = 1; it means a/an __________ process.
adiabatic
reversible
isothermal
none of these
isothermal
The melting point of paraffin wax (which contracts on solidification) __________ with pressure rise.
increases
decreases
remains unchanged
decreases linearly
increases
Co-efficient of Performance (COP) of a refrigerator is the ratio of the
work required to refrigeration obtained.
refrigeration obtained to the work required.
lower to higher temperature.
higher to lower temperature.
refrigeration obtained to the work required.
A solid metallic block weighing 5 kg has an initial temperature of 500°C. 40 kg of water initially at 25°C is contained in a perfectly insulated tank. The metallic block is brought into contact with water. Both of them come to equilibrium. Specific heat of block material is 0.4 kJ.kg-1. K-1. Ignoring the effect of expansion and contraction and also the heat capacity to tank, the total entropy change in kJ.kg-1 , K-1 is
-1.87
0
1.26
3.91
0
Trouton’s ratio of __________ liquids is calculated using Kistyakowsky equation.
polar
non-polar
both (a) & (b)
neither (a) nor (b)
non-polar
While dissolving a gas into a liquid at a constant temperature, the ratio of the concentration of the gas in the solution phase and in the gaseous phase is
infinity
unity
constant
negative
constant
Activity co-efficient is a measure of the
departure from ideal solution behaviour.
departure of gas phase from idea] gas law.
vapour pressure of liquid.
none of these.
departure from ideal solution behaviour.
Which of the following units is not present in both the vapor compression refrigeration system and absorption refrigeration system ?
Expansion valve
Condenser
Refrigerator
Compressor
Compressor
For an isothermal reversible compression of an ideal gas
only ΔE = 0
only ΔH =0
ΔE = ΔH = 0
dQ = dE
ΔE = ΔH = 0
Melting of ice exemplifies a/an
adiabatic process.
endothermic reaction.
exothermic reaction.
process involving a chemical reaction.
endothermic reaction.
A refrigeration cycle is the same as a __________ cycle,
turbine
heat engine
reversed heat engine
none of these
reversed heat engine
At __________ point, all the three phases (i.e.solid, liquid and gas) co-exist.
eutcetic
triple
plait
critical
triple
Kopp’s rule is used to calculate the heat capacity of ____.
solids
liquids
gases
all (a), (b) & (c)
solids
__________ explains the equilibrium constant for any chemical reaction.
Henry’s law
Law of mass action
Hess’s law
none of these
Law of mass action
Which of the following is not a reversible process ?
Expansion of an ideal gas against constant pressure.
Atmospheric pressure vaporisation of water at 100°C.
Solution of NaCl in water at 50°C.
None of these.
Solution of NaCl in water at 50°C.
Pick out the wrong statement.
A closed system does not permit exchange of mass with its surroundings but may permit exchange of energy.
An open system permits exchange of both mass and energy with its surroundings.
The term microstate is used to characterise an individual, whereas macro-state is used to designate a group of micro-states with common characteristics.
none of the above.
none of the above.
Which of the following exemplifies an adiabatic process ?
Melting of ice.
Condensation of alcohol vapor.
Sudden bursting of a cycle tube.
Evaporation of water.
Sudden bursting of a cycle tube.
Entropy, which is a measure of the disorder of a system is
independent of pressure.
independent of temperature.
zero at absolute zero temperature for a perfect crystalline substance.
all (a), (b) & (c)
zero at absolute zero temperature for a perfect crystalline substance.
Critical temperature is defined as the temperature above which a gas will
not liquify (barring exceptions).
immediately liquify.
never liquify however high the pressure may be.
none of these.
never liquify however high the pressure may be.
Gibbs-Duhem equation relates composition in liquid phase and the __________ at constant temperature & pressure.
fugacity
partial pressure
activity co-efficient
(a), (b), and (c)
(a), (b), and (c)
The standard Gibbs free energy change of a reaction depends on the equilibrium
pressure
temperature
composition
all (a), (b) and (c)
temperature
In an ideal solution, the activity of a component equals its
mole fraction.
fugacity at the same temperature and pressure.
partial pressure.
none of these.
mole fraction.
A gas has a volume of 27.3 c.c. at 0°C. Its volume at 10°C (if pressure remains unchanged) will be __________ c.c.
2.73
28.3
273
283
28.3
Clayperon equation deals with the
rate of change of vapour pressure with temperature.
effect of an inert gas on vapour pressure.
calculation of ΔF for spontaneous phase change.
temperature dependence of heat of phase transition.
rate of change of vapour pressure with temperature.
Gibbs free energy (G) is represented by, G= H - TS, whereas Helmholtz free energy, (A) is given by, A =E - TS. Which of the following is the Gibbs-Helmholtz equation
[ϑ(G/T)/ϑT] = -H/T^2
[ϑ(A/T)/ϑT]v = -E/T^2
both (a) and (b)
neither (a) nor (b)
both (a) and (b)
Which of the following is an undesirable characteristics of a refrigerant ?
It should be non-explosive.
It should have a sub-atmospheric vapor pressure at the temperature in refrigerator coils.
Its vapor pressure at the condenser temperature should be very high.
None of these.
It should have a sub-atmospheric vapor pressure at the temperature in refrigerator coils.
“The rate at which a substance reacts is proportional to its active mass and the rate of a chemical reaction is proportional to the product of active masses of the reacting substances”. This is the
Lewis-Randall rule.
statement of Vant-Hoff equation.
Le-Chatelier’s principle.
none of these.
none of these.
What is the ratio of adiabatic compressibility to isothermal compressibility ?
1
< 1
> 1
» 1
< 1
The absolute entropy for all crystalline substances at absolute zero temperature is
zero
negative
more than zero
indeterminate
zero
Pick out the wrong statement.
Phase rule variables are intensive properties.
Heat and work are both state function.
The work done by expansion of a gas in vacuum is zero.
CP and CV are state function.
Heat and work are both state function.
Compressibility factor of a gas is
not a function of its pressure.
not a function of its nature.
not a function of its temperature.
unity, if it follows PV = nRT.
unity, if it follows PV = nRT.
Which of the following is not an extensive property ?
Free energy
Entropy
Refractive index
None of these
Refractive index
Forward reaction will be favoured for the exothermic reaction, represented by CO + H2O CO2 + H2, by
low temperature and high pressure.
low temperature and low pressure.
high temperature and high pressure.
high temperature and low pressure.
low temperature and high pressure.
Enthalpy of a gas depends upon its
temperature
mass
volume
pressure
temperature
When dilute aqueous solutions of two salts are mixed, the process is associated with
decrease in temperature.
increase in temperature.
no change in temperature.
change in temperature which is a function of composition.
increase in temperature.
Pick out the correct statement.
Like internal energy and enthalphy, the absolute value of standard entropy for elementary substances is zero.
Melting of ice involves increase in enthalpy and a decrease in randomness.
The internal energy of an ideal gas depends only on its pressure.
Maximum work is done under reversible conditions.
Maximum work is done under reversible conditions.
Chemical engineering thermodynamics is concerned with the __________ in/of chemical processes.
reaction mechanism
calculation of rates
energy transformation from one form to the another
none of these
energy transformation from one form to the another
An isolated system can exchange __________ with its surroundings.
matter
energy
neither matter nor energy
both matter and energy
neither matter nor energy
Requisites of a reversible process is that the
system and surroundings pressure be equal.
friction in the system should be absent.
system and surroundings temperature be equal.
none of these.
friction in the system should be absent.
Fugacity is most helpful in
representing actual behaviour of real gases.
representing actual behaviour of ideal gases.
the study of chemical equilibria involving gases at atmospheric pressure.
none of these
representing actual behaviour of real gases.
The energy of activation of exothermic reaction is
zero.
negative.
very large compared to that for en-dothermic reaction.
not possible to predict.
not possible to predict.
Pick out the wrong statement.
The chemical potential of a pure substance depends upon the temperature and pressure.
The chemical potential of a component in a system is directly proportional to the escaping tendency of that component.
The chemical potential of ith species (μi) in an ideal gas mixture approaches zero as the pressure or mole fraction (xi) tends to be zero at constant temperature.
The chemical potential of species ‘i’ in the mixture (μi) is mathematically represented as, [eqn] , where, n, ni and nj respectively denote the total number of moles, moles of ith species and all mole numbers except ith species. ‘G’ is Gibbs molar free energy.
The chemical potential of ith species (μi) in an ideal gas mixture approaches zero as the pressure or mole fraction (xi) tends to be zero at constant temperature.
In the reaction; N2 + O2 → 2NO, increasing the pressure will result in
shifting the equilibrium towards right,
shifting the equilibrium towards left.
no change in equilibrium condition.
none of these.
no change in equilibrium condition.
A cyclic engine exchanges heat with two reservoirs maintained at 100 and 300°C respectively. The maximum work (in J) that can be obtained from 1000 J of heat extracted from the hot reservoir is
349
651
667
1000
349
Pick out the wrong statement.
Trouton’s ratio of non-polar liquids is calculated using Kistyakowasky equation.
Thermal efficiency of a Carnot engine is always less than 1.
An equation relating pressure, volume and temperature of a gas is called ideal gas equation.
none of these.
An equation relating pressure, volume and temperature of a gas is called ideal gas equation.
Which of the following is clausius-Clayperon equation for vaporisation of an ideal gas under the condition that the molar volume of liquid is negligible compared to that of the vapor ?
dlnp/dt = Hvap/RT^2
dlnp/dt = RT^2/Hvap
dp/dt = RT^2/Hvap
dP/dT = Hvapor/RT^2
dlnp/dt = Hvap/RT^2
When a gas is subjected to adiabatic expansion, it gets cooled due to
decrease in velocity.
decrease in temperature.
decrease in kinetic energy.
energy spent in doing work.
energy spent in doing work.
Joule-Thomson effect i.e., a throttling process is a constant __________ process.
entropy
temperature
internal energy
enthalpy
enthalpy
In the equation, PVn = Constant, if the value of n = 0, then it represents a reversible __________ process.
isobaric
isothermal
isentropic
isometric
isobaric
Work done in an adiabatic process between two states depends on the
rate of heat transmission
initial state only
end states only
none of these
end states only
The number of degree of freedom for an azeotropic mixture of ethanol and water in vapour-liquid equilibrium, is
3
1
2
0
1
The internal energy of an ideal gas is a function of its __________ only.
molecular size
volume
pressure
temperature
temperature
The change in __________ is equal to the reversible work for compression in steady state flow process under isothermal condition.
internal energy
enthalpy
Gibbs free energy
Helmholtz free energy
Gibbs free energy
Work done is a
property of the system
path function
point function
state description of a system
path function
Extensive properties of a thermodynamic system depend upon the __________ of the system.
specific volume
temperature
mass
pressure
mass
If an ideal solution is formed by mixing two pure liquids in any proportion, then the __________ of mixing is zero.
enthalpy
volume
both ‘a’ & ‘b’
neither ‘a’ nor ‘b’
both ‘a’ & ‘b’
Near their critical temperatures, all gases occupy volumes __________ that of the ideal gas.
less than
same as
more than
half
less than
The free energy change for a chemical reaction is given by (where, K = equilibrium constant)
RT lnK
-RT lnK
-R lnK
T lnK
-RT lnK
Free energy, fugacity and activity co-efficient are all affected by change in the temperature. The fugacity co-efficient of a gas at constant pressure ____with the increase of reduced temperature.
decreases
increases
remains constant
decreases logarithmically
increases
In the reaction, H2 +I2 2HI, addition of an inert gas will
increase the partial pressure of H2.
increase the partial pressure of I2.
increase the total pressure and hence shift the equilibrium towards the right.
not effect the equilibrium conditions
not effect the equilibrium conditions
What is the number of degrees of freedom for liquid water in equilibrium with a mixture of nitrogen and water vapor ?
2
0
3
1
2
The temperature at which a real gas obeys the ideal gas laws over a wide range of pressure is called the __________ temperature.
critical
Boyle
inversion
reduced
Boyle
If the molar heat capacities (Cp or Cv) of the reactants and products of a chemical reaction are identical, then, with the increase in temperature, the heat of reaction will
increase
decrease
remain unaltered
increase or decrease ; depends on the particular reaction
remain unaltered
All gases above its inversion temperature, in a throttling process will show
a heating effect.
no change in temperature.
a cooling effect.
either (a) or (c).
a heating effect.
First law of thermodynamics is mathematically stated as
dQ = dE + dW
dQ = dE - dW
dE = dQ + dW
dW = dQ + dE
dQ = dE + dW
Pick out the wrong statement.
Surface tension of a substance vanishes at critical point, as there is no distinction between liquid and vapour phases at its critical point.
Entropy of a system decreases with the evolution of heat.
Change of internal energy is negative for exothermic reactions.
The accentric factor for all materials is always more than one.
The accentric factor for all materials is always more than one.
Translational kinetic energy of molecules of an ideal gas is proportional to (where, T = absolute temperature of the gas )
T
√T
T^2
1/√T
T
Equation which relates pressure, volume and temperature of a gas is called the
equation of state
Gibbs Duhem equation
ideal gas equation
none of these
equation of state
Claussius-Clayperon equation gives accurate result, when the
vapour pressure is relatively low and the temperature does not vary over wide limits.
vapour obeys the ideal gas law and the latent heat of vaporisation is constant.
volume in the liquid state is negligible compared with that in the vapour state.
all (a), (b) and (c).
all (a), (b) and (c).
The temperature at which a real gas obeys the ideal gas laws over a wide range of pressure is called __________ temperature.
Boyle
inversion
critical
reduced
Boyle
For a single component two phase mixture, the number of independent variable properties are
two
one
zero
three
one
_________ law of thermodynamics ascertains the direction of a particular spontaneous process.
Zeroth
First
Second
Third
Second
At normal boiling point, molar entropy of vaporisation is __________ Joule/K°.mole.
72
92
142
192
92
For an ideal solution, the value of activity co-efficient is
0
1
< 1
> 1
1
The expression, nCv(T2 - T1), is for the __________ of an ideal gas.
work done under adiabatic condition
co-efficient of thermal expansion
compressibility
none of these
work done under adiabatic condition
The number of degrees of freedom at the triple point of water is
0
1
2
3
0
Which of the following is a widely used refrigerant in vapour compression refrigeration system (using large centrifugal compressor)?
Freon
Liquid sulphur dioxide
Methyl chloride
Ammonia
Freon
Internal energy is equal to the heat absorbed in case of a/an __________ process.
constant volume
polytropic
adiabatic
constant pressure
constant volume
The first law of thermodynamics is a restatement of the law of conservation of
mass
energy
momentum
none of these
energy
Joule-Thomson co-efficient for a perfect gas is
zero
positive
negative
none of these
zero
In an adiabatic process, the
heat transfer is zero.
temperature change is zero.
work done is a path function.
enthalpy remains constant.
heat transfer is zero.
A nozzle is a device, which
increases kinetic energy and decreases pressure.
reduces kinetic energy and increases pressure.
reduces both kinetic energy and pressure.
increases both kinetic energy and pressure.
increases kinetic energy and decreases pressure.
During the phase transition, __________ changes.
pressure
volume
temperature
all (a), (b) and (c)
volume
The work done in an adiabatic change in a particular gas depends upon changes in the __________ only.
temperature
specific heat
volume
pressure
temperature
The value of gas constant ‘R’ is
1.987 cal/gm mole °K
1.987 BTU/lb. mole °R
both (a) and (b)
neither (a) nor (b)
both (a) and (b)
In an isothermal process on an ideal gas, the pressure increases by 0.5 percent. The volume decreases by about __________ percent.
0.25
0.5
0.75
1
0.5
Which of the following is not a unit of the equilibrium constant Kp? (where, Δx = number of moles of products number of moles of reactants)
(atm)Δx, when Δx is negative
(atm)Δx, when Δx is positive
Dimensionless, when Δx = 0
(atm)Δx2, when Δx > 0
(atm)Δx2, when Δx > 0
Pick out the correct statement.
The available energy in an isolated system for all irreversible (real) processes decreases.
The efficiency of a Carnot engine increases, if the sink temperature is decreased.
The reversible work for compression in non-flow process under isothermal condition is the change in Helmholtz free energy.
all (a), (b) and (c)
all (a), (b) and (c)
Partial molal quantities are important in the study of
ideal gases
ideal solutions
non-ideal mixtures
a pure component
non-ideal mixtures
Number of degrees of freedom for a three phase system in equilibrium comprising of three non-reacting chemical species is
2
0
1
3
2
Critical solution temperature (or the con-solute temperature) for partially miscible liquids (e.g., phenol-water) is the minimum temperature at which
a homogeneous solution (say of phenol water) is formed.
mutual solubility of the two liquids shows a decreasing trend.
two liquids are completely separated into two layers.
none of these.
a homogeneous solution (say of phenol water) is formed.
Which is not constant for an ideal gas ?
(ϑP/ϑV)_T
(ϑV/ϑT)_P
(ϑP/ϑV)_V
all (a), (b) & (c)
(ϑP/ϑV)_T
Enthalpy ‘H’ is defined as
H = E - PV
H = F - TS
H - E = PV
none of these
H - E = PV
One ton of refrigeration is defined as the heat rate corresponding to melting of one ton of ice in one
hour
day
minute
second
day
_________ functions are exemplified by heat and work.
Path
Point
State
none of these
Path
In an irreversible process
Tds = dE - dW = 0
dE - dW - Tds = 0
Tds - dE + dW< 0
Tds - dT + dW< 0
Tds - dE + dW< 0
What is the number of degree of freedom for a system of two miscible non-reacting species in vapor-liquid equilibrium forming an azeotrope ?
3
2
1
0
1
The entropy change in a reversible isothermal process, when an ideal gas expands to four times its initial volume is
R loge 4
R log10 4
Cv log10 4
Cv loge 4
R loge 4
PVγ = Constant (where, γ = Cp/Cv) is valid for a/an __________ process.
isothermal
isentropic
isobaric
adiabatic
adiabatic
The heat capacities for the ideal gas state depend upon the
pressure
temperature
both (a) & (b)
neither (a) nor (b)
temperature
Which of the following will increase the volume of a real gas by four times ?
Doubling the absolute temperature as well as pressure of the gas.
Reducing pressure to one fourth at constant temperature.
Reducing temperature to one fourth at constant pressure.
Reducing the temperature to half and doubling the pressure.
Reducing pressure to one fourth at constant temperature.
Pick out the wrong statement.
A refriferation cycle violates the second law of thermadynamics.
Refrigeration cycle is normally represented by a temperature vs. entropy plot.
In a refrigerator, work required decreases as the temperature of the refrigerator and the temperature at which heat is rejected increases.
One ton of refrigeration is equivalent to the rate of heat absorption equal to 3.53 kW.
A refriferation cycle violates the second law of thermadynamics.
The equation, PV = nRT, is best obeyed by gases at
low pressure & high temperature.
high pressure & low temperature.
low pressure & low temperature.
none of these.
low pressure & high temperature.
Internal energy of an element at 1 atm and 25° C is __________ kcal/kg.mole.
0
273
25
none of these
0
Which of the following liquid metals has the highest thermal conductivity ?
Molten sodium
Molten lead
Mercury
Molten potassium
Molten sodium
Which of the following has the least thermal efficiency ?
Steam engine
Carnot engine
Diesel engine
Otto engine
Steam engine
Joule-Thomson Co-efficient at any point on the inversion curve is
∞
+ ve
0
-ve
0
Pick out the wrong statement.
The values of (ϑP/ϑV)_T and (ϑ2P/ϑV2)_T are zero for a real gas at its critical point.
Heat transferred is equal to the change in the enthalpy of the system, for a constant pressure, non-flow, mechanically reversible process.
Thermal efficiency of a Carnot engine depends upon the properties of the working fluid besides the source & sink temperatures.
During a reversible adiabatic process, the entropy of a substance remains constant.
Thermal efficiency of a Carnot engine depends upon the properties of the working fluid besides the source & sink temperatures.
Number of components (C), phase (P) and degrees of freedom (F) are related by Gibbs phase rule as
P + F - C = 2
C = P - F + 2
F = C - P - 2
P = F - C - 2
P + F - C = 2
The value of Cp & Cv respectively for monoatomic gases in Kcal/kg Mole . °K are
5 & 3
3.987 & 1.987
1.987 & 0.66
0.66 & 1.987
5 & 3
(ϑT/ϑP)_H is the mathematical expression for
specific heat at constant pressure (Cp).
specific heat at constant volume (Cv).
Joule-Thompson co-efficient.
none of these.
Joule-Thompson co-efficient.
In case of a close thermodynamic system, there is __________ across the boundaries.
no heat and mass transfer
no mass transfer but heat transfer
mass and energy transfer
none of these
no mass transfer but heat transfer
During a reversible isothermal expansion of an ideal gas, the entropy change is
+ve
0
-ve
∞
+ve
As the temperature is lowered towards the absolute zero, the value of ϑ(ΔF)/ϑT, then approaches
unity
zero
that of the heat of reaction
infinity
zero
The ratio of equilibrium constants (Kp2/Kp1) at two different temperatures is given by
R/ΔH[1/T1-1/T2]
ΔH/R[1/T1-1/T2]
ΔH/R[1/T2-1/T1]
1/R[1/T1-1/T2]
ΔH/R[1/T1-1/T2]
Which of the following is not affected by temperature changes ?
Fugacity
Activity co-efficient
Free energy
None of these
None of these
For an ideal gas, the activity co-efficient is
directly proportional to pressure.
inversely proportional to pressure.
unity at all pressures.
none of these.
unity at all pressures.
Those solutions in which there is no volume change upon mixing the components in the liquid state and which, when diluted do not undergo any heat change (i.e. heat of dilution is zero), are called __________ solutions.
ideal
real
isotonic
none of these
ideal
