Thermodynamics Flashcards
Maximum work that could be secured by expanding the gas over a given pressure range is the __________ work.
isothermal
Internal energy change of a system over one complete cycle in a cyclic process is
zero
Heating of water under atmospheric pressure is an __________ process.
isobaric
Van Laar equation deals with the activity co-efficients in
binary solutions
High __________ is an undesirable property for a good refrigerant.
viscosity
Solubility of a substance which dissolves with an increase in volume and liberation of heat will be favoured by the
low pressure and low temperature.
Entropy is a measure of the __________ of a system.
disorder
A chemical reaction will occur spontaneously at constant pressure and temperature, if the free energy is
negative
Fundamental principle of refrigeration is based on the __________ law of thermodynamics.
second
For a spontaneous process, free energy
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 ?
Carnot refrigeration cycle.
In a working refrigerator, the value of COP is always
> 1
A refrigerator may be termed as a
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.
increases
Which of the following is not an intensive property ?
Heat capacity
Out of the following refrigration cycles, which one has the minimum COP (Co-efficient of performance)?
Air cycle
Measurement of thermodynamic property of temperature is facilitated by __________ law of thermodynamics.
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
-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.
327
Isobaric process means a constant process.
pressure
No work is done by the system, when a reaction occurs at constant
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
Clayperon-Claussius equation
The freezing point of a liquid decreases when the pressure is increased, if the liquid __________ while freezing.
contracts
“At the absolute zero temperature, the entropy of every perfectly crystalline substance becomes zero”. This follows from the
third law of thermodynamics
During Joule-Thomson expansion of gases
enthalpy remains constant.
The accentric factor of a materical, ‘ω’, is defined as ω = -log10(Pr^sat)Tr^-1 = 0.7, where, Pr^sat = reduced vapor pressure, Tr = reduced temperature. The value of accentric factor is always
< 1
“Law of corresponding states” says that
, 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
Pick out the wrong statement pertaining to the decomposition of PCl5 represented by, PCl5 ⇌ PCl3 + Cl2.Degree of dissociation of PCl5 will
none of these
Boyle’s law for gases states that
(1) , when temperature & mass of the gas remain constant.
1st law of thermodynamics is nothing but the law of conservation of
energy
In a reversible chemical reaction (where, Δx = number of moles of products-number of moles of reactants )
all of these
Out of the following refrigeration cycles, which one has maximum COP ?
Carnot cycle
Pick out the correct statement:
Under reversible conditions, the adiabatic work is less than isothermal work.
In any spontaneous process,
both F and A decreases
Which of the following is a thermodynamic property of a system ?
Entropy
Equilibrium constant decreases as the temperature
increases, for an exothermic reaction.
The expression, (1) , gives the free energy change
with pressure changes at constant temperature.
All gases during throttling process at atmospheric temperature and pressure show a cooling effect except
H2
Compressibility factor for almost all the gases are approximately same at the same
reduced pressure and reduced temperature.
Pick out the wrong statement.
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.
none of these
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
all of these
In jet refrigerators, the refrigerating fluid is practically always
water
Water on heating from 1 to 4°C
contracts
Pick out the correct statement.
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, ice<—->water, then
more water will be formed.
Partial molar free energy of an element A in solution is same as its
chemical potential
Free energy change at equilibrium is
zero
The temperature at which both liquid and gas phases are identical, is called the __________ point.
critical
What is the value of ln y (where y = activity co-efficient) for ideal gases ?
Zero
A closed system is cooled reversibly from 100°C to 50°C. If no work is done on the system
U and S both decreases
Which is not a refrigerant ?
C2H4Cl2
The partial pressure of each constituent present in an alloy is __________ the total vapor pressure exerted by the alloy.
less than
The four properties of a system viz. P, V, T, S are related by __________ equation.
Maxwell’s
If the pressure on 100 c.c. of air is halved, then its volume (at the same temperature) would be __________ c.c.
200
Pick out the wrong statement.
The heat capacity of solid inorganic substance is exactly equal to the heat capacity of the substance in the molten state.
The number of degrees of freedom for an azeotropic mixture in a two component vapour-liquid equilibria is/are
one
Any substance above its critical temperature exists as
gas
Which of the following decreases with increase in pressure ?
Melting point of ice
Isentropic process means a constant __________ process.
entropy .
(1) is the mathematical expression
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 = 1
A liquid under pressure greater than its vapour pressure for the temperature involved is called a __________ liquid.
subcooled
For a real gas, the chemical potential is given by
RT dlnf
At absolute zero temperature, all substances have the same
heat capacity
Lowering of condenser temperature (keeping the evaporator temperature constant) in case of vapour compression refrigeration system results in
increased COP.
Pick out the correct statement.
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
1160
The thermodynamic law, PVy = constant, is not applicable in case of
free expansion of an ideal gas.
Mollier diagram is a plot of
entropy vs. enthalpy
is the mathematical expression for
none of these
The activity of an ideal gas is numerically __________ its pressure.
equal to
Specific heat of a gas for a reversible adiabatic process is
zero
When a gas in a vessel expands, its internal energy decreases. The process involved is
reversible
A system is said to be isopiestic, if there is no __________ change.
pressure
In a turbine, the fluid expands almost
adiabatically
The unity of Planck’s constant ‘h’ in the equation, E = hv is
J.S
Specific/molar Gibbs free energy for a pure substance does not change during
either (a), (b) or (c)
Refrigeration capacity of a household refrigerator may be round about __________ tons.
0.15
(1) is the mathematical expression for
none of these
An ideal gas is taken around the cycle ABCA as shown in P-V diagram below :The work done by the gas during the cycle is equal to
3 P1V1
In polytropic process (PVn = constant), if n = 1; it means a/an __________ process.
isothermal
The melting point of paraffin wax (which contracts on solidification) __________ with pressure rise.
increases
Co-efficient of Performance (COP) of a refrigerator is the ratio of the
refrigeration obtained to the work required.
dW and dq are not the exact differential, because q and W are
path functions
Activity co-efficient is a measure of the
departure from ideal solution behaviour.
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
constant
Which of the following units is not present in both the vapor compression refrigeration system and absorption refrigeration system ?
Compressor
For an isothermal reversible compression of an ideal gas
ΔE = ΔH = 0
Melting of ice exemplifies a/an
endothermic reaction.
A refrigeration cycle is the same as a __________ cycle,
reversed heat engine
At __________ point, all the three phases (i.e.solid, liquid and gas) co-exist.
triple
Kopp’s rule is used to calculate the heat capacity of
solids
__________ explains the equilibrium constant for any chemical reaction.
Law of mass action
Which of the following is not a reversible process ?
Solution of NaCl in water at 50°C.
Pick out the wrong statement.
none of the above.
Which of the following exemplifies an adiabatic process ?
Sudden bursting of a cycle tube.
Entropy, which is a measure of the disorder of a system is
zero at absolute zero temperature for a perfect crystalline substance.
Critical temperature is defined as the temperature above which a gas will
never liquify however high the pressure may be.
The standard Gibbs free energy change of a reaction depends on the equilibrium
temperature
Gibbs-Duhem equation relates composition in liquid phase and the __________ at constant temperature & pressure.
(a), (b), and (c)
In an ideal solution, the activity of a component equals its
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.
28.3
Clayperon equation deals with the
rate of change of vapour pressure with temperature.
Which of the following is an undesirable characteristics of a refrigerant ?
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
none of these.
What is the ratio of adiabatic compressibility to isothermal compressibility ?
< 1
The absolute entropy for all crystalline substances at absolute zero temperature is
zero
Pick out the wrong statement.
Heat and work are both state function.
Compressibility factor of a gas is
unity, if it follows PV = nRT.
Which of the following is not an extensive property ?
Refractive index
Forward reaction will be favoured for the exothermic reaction, represented by CO + H2O ⇌ CO2 + H2, by
low temperature and high pressure.
Enthalpy of a gas depends upon its
temperature
When dilute aqueous solutions of two salts are mixed, the process is associated with
increase in temperature.
Pick out the correct statement.
Maximum work is done under reversible conditions.
Chemical engineering thermodynamics is concerned with the __________ in/of chemical processes.
energy transformation from one form to the another
An isolated system can exchange __________ with its surroundings.
neither matter nor energy
Requisites of a reversible process is that the
friction in the system should be absent.
Fugacity is most helpful in
representing actual behaviour of real gases.
The energy of activation of exothermic reaction is
not possible to predict.
Pick out the wrong statement.
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 (1) 2NO, increasing the pressure will result in
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
Pick out the wrong statement.
An equation relating pressure, volume and temperature of a gas is called ideal gas equation.
When a gas is subjected to adiabatic expansion, it gets cooled due to
energy spent in doing work.
Joule-Thomson effect i.e., a throttling process is a constant __________ process.
enthalpy
In the equation, PV^n = Constant, if the value of n = 0, then it represents a reversible __________ process.
isobaric
Work done in an adiabatic process between two states depends on the
end states only
The number of degree of freedom for an azeotropic mixture of ethanol and water in vapour-liquid equilibrium, is
1
The internal energy of an ideal gas is a function of its __________ only.
temperature
At constant temperature and pressure, for one mole of a pure substance, the ratio of the free energy to the chemical potential is
one
The change in __________ is equal to the reversible work for compression in steady state flow process under isothermal condition.
Gibbs free energy
Work done is a
path function
Extensive properties of a thermodynamic system depend upon the __________ of the system.
mass
Near their critical temperatures, all gases occupy volumes __________ that of the ideal gas.
less than
The free energy change for a chemical reaction is given by (where, K = equilibrium constant)
-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.
increases
In the reaction, H2 +I2 ⇌ 2HI, addition of an inert gas will
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
The temperature at which a real gas obeys the ideal gas laws over a wide range of pressure is called the __________ temperature.
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
remain unaltered
All gases above its inversion temperature, in a throttling process will show
a heating effect.
First law of thermodynamics is mathematically stated as
dQ = dE + dW
Pick out the wrong statement.
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
Equation which relates pressure, volume and temperature of a gas is called the
equation of state
Claussius-Clayperon equation gives accurate result, when the
all of these
The temperature at which a real gas obeys the ideal gas laws over a wide range of pressure is called __________ temperature.
Boyle
For a single component two phase mixture, the number of independent variable properties are
one
__________ law of thermodynamics ascertains the direction of a particular spontaneous process.
Second
At normal boiling point, molar entropy of vaporisation is __________ Joule/K°.mole.
92
For an ideal solution, the value of activity co-efficient is
1
The expression, nCv(T2 - T1), is for the __________ of an ideal gas.
work done under adiabatic condition
Which of the following is a widely used refrigerant in vapour compression refrigeration system (using large centrifugal compressor)?
Freon
Internal energy is equal to the heat absorbed in case of a/an __________ process.
constant volume
The first law of thermodynamics is a restatement of the law of conservation of
mass
Joule-Thomson co-efficient for a perfect gas is
positive
In an adiabatic process, the
heat transfer is zero.
A nozzle is a device, which
increases kinetic energy and decreases pressure.
Duringthe phase transition, __________ changes.
volume
The work done in an adiabatic change in a particular gas depends upon changes in the __________ only.
temperature
In an isothermal process on an ideal gas, the pressure increases by 0.5 percent. The volume decreases by about __________ percent.
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)Δx2, when Δx > 0
Pick out the correct statement.
all of these
Partial molal quantities are important in the study of
non-ideal mixtures
Number of degrees of freedom for a three phase system in equilibrium comprising of three non-reacting chemical species is
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.
Enthalpy ‘H’ is defined as
H - E = PV
One ton of refrigeration is defined as the heat rate corresponding to melting of one ton of ice in one
day
__________ functions are exemplified by heat and work.
Path
In an irreversible process
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 ?
1
The entropy change in a reversible isothermal process, when an ideal gas expands to four times its initial volume is
R loge 4
PVγ = Constant (where, γ = Cp/Cv) is valid for a/an __________ process.
adiabatic
Claude gas liquefaction process employs cooling
by expansion in an engine.
Which of the following will increase the volume of a real gas by four times ?
Reducing pressure to one fourth at constant temperature.
Pick out the wrong statement.
A refriferation cycle violates the second law of thermadynamics.
The equation, PV = nRT, is best obeyed by gases at
low pressure & high temperature.
Which of the following liquid metals has the highest thermal conductivity ?
Molten sodium
Which of the following has the least thermal efficiency ?
Steam engine
Pick out the wrong statement.
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
The value of Cp & Cv respectively for monoatomic gases in Kcal/kg Mole . °K are
5 & 3
(1) is the mathematical expression for
Joule-Thompson co-efficient.
In case of a close thermodynamic system, there is __________ across the boundaries.
no mass transfer but heat transfer
During a reversible isothermal expansion of an ideal gas, the entropy change is
+ve
As the temperature is lowered towards the absolute zero, the value of (1), then approaches
zero
Which of the following is not affected by temperature changes ?
None of these
