ChE Thermodynamics Flashcards
Which of the following is an extensive property of a system?
A. Heat capacity
B. Molal heat capacity
C. Pressure
D. Concentration
A. Heat capacity
Which of the following is a thermodynamic property of a system?
A. Concentration
B. Mass
C. Temperature
D. Entropy
D. Entropy
First law of thermodynamics is mathematically stated as
A. dQ = dU + dW
B. dQ = dU - dW
C. dU = dQ + dW
D. dW = dQ - dU
A. dQ = dU + dW
First law of thermodynamics deals with
A. Direction of energy transfer
B. Reversible process only
C. Irreversible process only
D. None of these
A. Direction of energy transfer
An irreversible process
A. Is the analog of linear frictionless motion in machines
B. Is an idealized visualization of behavior of a system
C. Yields the maximum amount of work
D. Yields the amount of work less than that of a reversible process
D. Yields the amount of work less than that of a reversible process
In an adiabatic process
A. Heat transfer is zero
B. Temperature change is zero
C. Work done is a path function
D. Enthalpy remains constant
A. Heat transfer is zero
Enthalpy ‘H’ is defined as
A. H = U - PV
B. H = U - TS
C. H - U = PV
D. None of these
C. H - U = PV
Efficiency of a heat engine working on Carnot cycle between two temperature levels depends upon
A. The two temperatures only
B. The pressure of working fluid
C. The mass of the working fluid
D. Both mass and pressure of the working fluid
A. The two temperatures only
What is the degree of freedom for a system comprising liquid water equilibrium with its vapor?
A. 0
B. 1
C. 2
D. 3
B. 1
Efficiency of a Carnot engine working between temperatures T1 and T2 (T1 < T2) is
A. (T2 - T1)/T2
B. (T2 - T1)/T1
C. (T1 - T2)/T2
D. (T1 - T2)/T1
A. (T2 - T1)/T2
For a constant pressure reversible process, the enthalpy (ΔH) change of the system is
A. CvdT
B. CpdT
C. ∫Cp dT
D. ∫Cv dT
C. ∫Cp dT
Internal energy of an ideal gas
A. Increases with increase in pressure
B. Decreases with increase in temperature
C. Is independent of temperature
D. None of these
D. None of these
Equation that relates pressure, volume, and temperature of a gas is called
A. Equation of state
B. Gibbs-Duhem equation
C. Ideal gas equation
D. None of these
A. Equation of state
Isobaric process means a constant
A. Temperature process
B. Pressure process
C. Volume process
D. Entropy process
B. Pressure process
Isentropic process means constant
A. Enthalpy process
B. Pressure process
C. Volume process
D. None of these
C. Volume process
Throttling process is a constant
A. Enthalpy process
B. Entropy process
C. Pressure process
D. None of these
A. Enthalpy process
The point at which all three phases co-exist is known as
A. Freezing point
B. Triple point
C. Boiling point
D. None of these
B. Triple point
C, for an ideal gas
A. Does not depend upon temperature
B. Is independent of pressure only
C. Is independent of volume only
D. Is independent of both pressure and volume
D. Is independent of both pressure and volume
For an isothermal process, the internal energy of a gas
A. Increases
B. Decreases
C. Remains unchanged
D. Data insufficient; can’t be predicted
C. Remains unchanged
PV^γ = constant (where γ = Cp/Cv) is valid for
A. Isothermal process
B. Isentropic process
C. Isobaric process
D. Adiabatic process
D. Adiabatic process
For an isothermal reversible compression of an ideal gas
A. only ΔU = 0
B. only ΔH = 0
C. ΔU = ΔH = 0
D. dQ - dU
C. ΔU = ΔH = 0
As time is passing, entropy of the universe
A. Is increasing
B. Is decreasing
C. Remains constant
D. Data insufficient; can’t be predicted
A. Is increasing
Boyle’s law for gases states that
A. P ∝ 1/V when temperature is constant
B. P ∝ 1/V when temperature and mass of the gas remains constant
C. P ∝ V at a constant temperature and mass of the gas
D. P/V = constant, for any gas
B. P ∝ 1/V when temperature and mass of the gas remains constant
The equation PV = nRT is best obeyed by gases at
A. Low pressure and high temperature
B. High pressure and low temperature
C. Low pressure and low temperature
D. None of these
A. Low pressure and high temperature
Compressibility factor of gas is
A. Not a function of pressure
B. Not a function of its nature
C. Not a function of its temperature
D. Unity, if it follows PV = nRT
A. Not a function of pressure
Critical compressibility factor for all substances
A. Are more less constant (vary from 0.2 to 0.3)
B. Vary as square of the absolute temperature
C. Vary as square of the absolute pressure
D. None of these
A. Are more less constant (vary from 0.2 to 0.3)
Reduced pressure of a gas is the ratio of its
A. Pressure to critical pressure
B. Critical pressure to pressure
C. Pressure to pseudocritical pressure
D. Pseudocritical pressure to pressure
A. Pressure to critical pressure
Compressibility factor-reduced pressure plot on reduced coordinates facilities
A. Use only one graph for all gases
B. Covering of wider range
C. Easier plotting
D. More accurate plotting
A. Use only one graph for all gases
Number of components (C), phases (P), and degrees of freedom (F) are related by Gibbs phase rule as
A. P + F - C = 2
B. C = P - F + 2
C. F = C - P - 2
D. P = F - C - 2
A. P + F - C = 2
The degrees of freedom at triple point will be
A. 0
B. 1
C. 2
D. 3
A. 0
Cp - Cv = R is valid for
A. Ideal gases
B. All gases
C. Gases at very high pressure
D. Gases at very low temperature
A. Ideal gases
An isolated system can exchange
A. Matter with its surroundings
B. Energy with its surroundings
C. Neither matter nor energy with its surroundings
D. Both matter nor energy with its surroundings
C. Neither matter nor energy with its surroundings
Heat of formation of an element in its standard state is
A. 0
B. < 0
C. > 0
D. A function of pressure
A. 0
Heat of reaction is
A. Dependent on pressure only
B. Dependent on temperature only
C. Dependent on both pressure and temperature
D. Independent of temperature changes
C. Dependent on both pressure and temperature
Second law of thermodynamics s is concerned with
A. Amount of energy transferred
B. Direction of energy transferred
C. Irreversible process only
D. Non-cyclic process only
B. Direction of energy transferred
The absolute entropy for all crystalline substances at absolute zero temperature
A. Is zero
B. Is negative
C. Is more than zero
D. Can’t be determined
A. Is zero
Joule-Thomson coefficient is defined as
A. µ = (∂P/∂T)_H
B. µ = (∂T/∂P)_H
C. µ = (∂U/∂T)_H
D. µ = (∂U/∂P)_H
B. µ = (∂T/∂P)_H
Mollier diagram is a plot of
A. Temperature vs. enthalpy
B. Temperature vs. entropy
C. Entropy vs. enthalpy
D. Temperature vs. internal energy
C. Entropy vs. enthalpy
Near their critical temperature all gases, occupy volumes ____ that of the ideal gas
A. Less than
B. Same as
C. More than
D. Half
A. Less than
Charles law for gases states that
A. V/T = constant
B. V ∝ 1/T
C. V ∝ 1/P
D. PV/T = constant
A. V/T = constant
Absolute zero temperature signifies
A. Minimum temperature attainable
B. The temperature of the heat reservoir to which a Carnot engine rejects all the heat that is taken in
C. The temperature of the heat reservoir to which a Carnot engine rejects no heat
D. None of these
C. The temperature of the heat reservoir to which a Carnot engine rejects no heat
Entropy is a measure of
A. Disorder of a system
B. Orderly behavior of a system
C. Only temperature changes of the system
D. None of these
A. Disorder of a system
For spontaneous changes in an isolated system (S = entropy)
A. dS = 0
B. dS < 0
C. dS > 0
D. dS = constant
C. dS > 0
For equilibrium process in an isolated system
A. dS = 0
B. dS < 0
C. dS > 0
D. dS = constant
A. dS = 0
The four properties of a system via P, V, T, S are related by
A. Gibbs-Duhem equation
B. Gibbs-Helmholtz equation
C. Maxwell’s equation
D. None of these
C. Maxwell’s equation
For a constant volume process
A. dU = Cp dT
B. dU = Cv dT
C. dQ = dU + pdV
D. dW = pdV
B. dU = Cv dT
In a reversible process
A. TdS = dU + dW
B. dU - dW = TdS
C. dW - dU = TdS
D. TdS - dW - dU > 0
A. TdS = dU + dW
In an irreversible process
A. TdS = UdW = 0
B. dU - dW - TdS = 0
C. TdS - dU - dW < 0
D. TdS - dT + dW <0
C. TdS - dU - dW < 0
Cv is given by
A. (∂U/∂T)_V
B. (∂U/∂V)_T
C. (∂U/∂P)_V
D. (∂V/∂T)_P
A. (∂U/∂T)_V
Third law of thermodynamics is concerned with
A. The value of absolute entropy
B. Energy transfer
C. Direction of energy transfer
D. None of these
A. The value of absolute entropy
Which of the following equation is obtained on combining 1st and 2nd law of thermodynamics, for a system of constant mass?
A. dU = TdS - PdV
B. dQ = CvdT + PdV
C. dQ = CpdT + VdP
D. TdS = dU - PdV
A. dU = TdS - PdV
The equation TdS = dU - PdV applies to
A. Single-phase fluid of varying composition
B. Single-phase fluid of constant composition
C. Open as well as closed systems
D. Both b and c
D. Both b and c
For an exothermic reaction
A. Only enthalpy change (ΔH) is negative
B. Only internal energy change (ΔU) is negative
C. Both ΔH and ΔU are negative
D. Enthalpy change is zero
C. Both ΔH and ΔU are negative
If different processes are used to bring about the same chemical reaction, the enthalpy change is same for all of them
A. Hess’s law
B. Kirchhoff’s law
C. Lavoisier and Laplace law
D. None of these
A. Hess’s law
Change of heat content when one mole of the compound is burnt in oxygen at constant pressure is called
A. Calorific value
B. Heat of reaction
C. Heat of combustion
D. Heat of transformation
C. Heat of combustion
Melting of wax is accompanied with
A. Increase in entropy
B. Decrease in entropy
C. Constant entropy
D. None of these
A. Increase in entropy
Helmholtz free energy is defined as
A. A = H - TS
B. A = U - TS
C. A = H + TS
D. None of these
B. A = U - TS
Gibbs free energy (G) is defined as
A. G = U - TS
B. G = H - TS
C. G = H + TS
D. G = U + TS
B. G = H - TS
Gibbs-Helmholtz equation is
A. ΔG = ΔH + T[∂(ΔG)/(∂T]_P
B. ΔG = ΔH - TΔT
C. d(U - TS)T, V < 0
D. dP/dT = ΔHvap/TΔVvap
A. ΔG = ΔH + T[∂(ΔG)/(∂T]_P
For a reversible process involving only pressure-volume work
A. (dG)_T, p < 0
B. (dG)_T, p > 0
C. (dG)_T, p = 0
D. (dA)_T, v > 0
C. (dG)_T, p = 0
For an irreversible process involving only pressure-volume work
A. (dG)_T, p < 0
B. (dG)_T, p > 0
C. (dG)_T, p = 0
D. (dA)_T, v > 0
A. (dG)_T, p < 0
Pick out the correct equation relating G and A
A. G = A + PV
B. G = U + A
C. G + A - TS
D. G = A + TS
A. G = A + PV
A chemical reaction will occur spontaneously at constant pressure and temperature, if free energy is
A. Zero
B. Positive
C. Negative
D. None of these
C. Negative
Clapeyron equation deals with the
A. Rate of change of vapor pressure with temperature
B. Effect of an inert gas on vapor pressure
C. Calculation of G for spontaneous phase change
D. Temperature dependence of least of phase transition
A. Rate of change of vapor pressure with temperature
In any spontaneous process
A. Only G decreases
B. Only A decreases
C. Both G and A decreases
D. Both G and A increases
C. Both G and A decreases
Pick out the Claussius-Clapeyron equation from the following:
A. dP/dT = ΔH/T ΔV
B. ln P = - ΔH/RT + constant
C. ΔG = ΔH + T[∂(ΔG)/(∂T]_P
D, None of these
B. ln P = - ΔH/RT + constant
Free energy charges for two reaction mechanism X and Y are respectively -15 and 5 units. It implies that X is
A. Slower than Y
B. Faster than Y
C. Three times slower than Y
D. Three times faster than Y
B. Faster than Y
Chemical potential is
A. An extensive property
B. An intensive property
C. A force which derives the chemical system to equilibrium
D. Both b and c
D. Both b and c
Chemical potential of its component of a system is given by
A. μi = (∂G/∂ni)_T,P,ni
B. μi = (∂A/∂ni)_T,P,ni
C. μi = (∂G/∂ni)_T,P
D. μi = (∂A/∂ni)_T,P,
A. μi = (∂G/∂ni)_T,P,ni
The chemical potential for a pure substance _____ its partial molal free energy
A. More than
B. Less than
C. Equal to
D. Not related to
C. Equal to
Partial molal quantities are important in the study of
A. Ideal gases
B. Ideal solutions
C. Non-ideal mixtures
D. A pure component
C. Non-ideal mixtures
Fugacity and pressure are numerically equal when the gas is
A. In standard state
B. At high temperature
C. At low temperature
D. In idea state
D. In ideal state
The relation connecting the fugacities of various components in a solution with one another to composition at constant temperature and pressure is called
A. Gibbs-Duhem equation
B. Van Laar equation
C. Gibbs-Helmholtz equation
D. Margules equation
A. Gibbs-Duhem equation
The necessary condition for phase equilibrium in a multi phase system of N components is the
A. Chemical potential of all components should be equal in all phases
B. Chemical potentials of all components should be the same in a particular phase
C. Sum of the chemical potentials of any given component in all the phases should be the same
D. None of these
A. Chemical potential of all components should be equal in all phases
Which of the following is not affected by temperature changes?
A. Fugacity
B. Activity co-efficient
C. Free energy
D. None of these
D. None of these
The activity of an ideal gas is numerically
A. More than its pressure
B. Less than its pressure
C. Equal to its pressure
D. Data insufficient, can’t be predicted
C. Equal to its pressure
Maximum work that could be secured by expanding the gas over a given pressure range is the
A. Isothermal work
B. Adiabatic work
C. Isentropic work
D. None of these
A. Isothermal work
The point at which both liquid and gas phases are identical is called
A. Critical point
B. Triple point
C. Freezing
D. Boiling point
A. Critical point
Equilibrium constant of a reaction varies with
A. Initial concentration of the reactant
B. Pressure
C. Temperature
D. None of these
C. Temperature
For an ideal solution, the value of activity coefficient is
A. 0
B. 1
C. < 1
D. > 1
B. 1
Fugacity coefficient of a substance is the ratio of its fugacity to
A. Mole fraction
B. Activity
C. Pressure
D. Activity coefficient
C. Pressure
Van Laar equation deals with activity coefficients in
A. Binary solution
B. Ternary solution
C. Azeotropic mixture only
D. None of these
A. Binary solution
In Joule-Thomson porous plug experiment
A. Enthalpy does not remain constant
B. The entire apparatus is exposed to surroundings
C. Temperature remains constant
D. None of these
D. None of these
Equilibrium constant
A. Decreases as the temperature increases for an exothermic reaction
B. Decreases as the temperature decreases for an exothermic reaction
C. Will decrease with increasing temperature for an exothermic reaction
D. None of these
A. Decreases as the temperature increases for an exothermic reaction
As the entropy of the universe is increasing day by day, the work producing capacity of a heat engine is
A. Not changed
B. Decreasing
C. Increasing
D. Data insufficient; can’t be predicted
B. Decreasing
Refrigeration cycle
A. Violates second law of thermodynamics
B. Involves transfer of heat from low temperature to high temperature
C. Both a and b
D. None of these
B. Involves transfer of heat from low temperature to high temperature
Ideal refrigeration cycle is
A. Same as Carnot cycle
B. Same as reverse Carnot cycle
C. Dependent on refrigerant properties
D. The least efficient of all refrigeration processes
B. Same as reverse Carnot cycle
Fundamental principle of refrigeration is based on
A. Zeroth law of thermodynamics
B. First law of thermodynamics
C. Second law of thermodynamics
D. Third law of thermodynamics
C. Second law of thermodynamics
Coefficient of Performance (COP) of a refrigerator is the ratio of
A. Work required to refrigeration obtained
B. Refrigeration obtained to the work required
C. Lower to higher temperature
D. Higher to lower temperature
B. Refrigeration obtained to the work required
In a working refrigerator, value of COP is always
A. 0
B. < 0
C. < 1
D. > 1
D. > 1
One tone of refrigeration capacity is equivalent to
A. 50 kcal/hr
B. 200 BTU/hr
C. 200 BTU/min
D. 200 BTU/day
C. 200 BTU/min
Which of the following hvae minimum value of COP for a given refrigeration effect?
A. Reverse Carnot cycle
B. Ordinary vapor compression cycle
C. Vapor compression process with a reversible expansion engine
D. Air refrigeration cycle
D. Air refrigeration cycle
An ideal refrigerant should
A. Not have a subatmosphere vapor pressure at the temperature in the refrigerator coils
B. Not have unduly high vapor pressure at the condenser temperature
C. Both a and b
D. None of these
C. Both a and b
Heat pump
A. Accomplishes only space heating in winter
B. Accomplishes only space cooling in summer
C. Accomplishes both a and b
D. Work on Carnot cycle
C. Accomplishes both a and b
Which of the following is not a common refrigerant
A. Freon 12
B. Ethylene
C. Ammonia
D. Carbon dioxide
B. Ethylene
Domestic refrigerator usually works on
A. Carnot refrigeration cycle
B. A refrigeration cycle
C. Absorption refrigeration cycle
D. Vapor ejection refrigeration
C. Absorption refrigeration cycle
Refrigerants commonly used for domestic refrigeration are
A. Ethyl chloride
B. Freon 12
C. Propane
D. CO2
B. Freon 12
Air refrigeration cycle
A. Is most efficient of all refrigeration
B. Has very low efficiency
C. Requires relatively quantities of air to achieve a significant amount of refrigeration
D. Both b and c
D. Both b and c
Coefficient of Performance for a reversed Carnot cycle working between temperatures T1 and T2 (T1 > T2)
A. T2/(T1 - T2)
B. T1/(T1 - T2)
C. (T2 - T1)/T1
D (T1 - T2)/T2
A. T2/(T1 - T2)
Dry ice is
A. Moisture free ice
B. Solid helium
C. Solid carbon dioxide
D. None of these
C. Solid carbon dioxide
