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THERMODYNAMICS > TOP > Flashcards

TOP Flashcards

1
Q

Heat effects characterized by phase transition

a. Latent Heat
b. Heat of combustion
c. Sensible heat
d. Heat of formation

A

a. Latent Heat

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2
Q

Heat effects characterized by changes in temperature

a. Latent Heat
b. Heat of combustion
c. Sensible heat
d. Heat of formation

A

c. Sensible heat

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3
Q

At the critical point, Cubic Equations of State have

a. 3 solutions, 1 value
b. 3 solutions, 1 for vapor, 1 for liquid, 1 without meaning
c. 3 solutions, all imaginary
d. 3 solutions, 1 imaginary

A

a. 3 solutions, 1 value

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4
Q

A 2-stage cascade refrigeration system is used to cool a room with cycle 1 adjacent to the outside surrounding at TS operates at TH and TC while cycle 2 adjacent to the room at TR operates at T’H and T’C. Which of the following is true?

a. T’C > T’H
b. T’H > TS
c. T’C > TR
d. T’H > TH

A

c. T’C > TR

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5
Q

Which of the following are considered to be energy in transit?

a. Kinetic energy
b. Internal energy
c. Potential energy
d. Heat

A

d. Heat

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6
Q

A liquid property which relates the change in volume with respect to changes in pressure at a constant temperature.

a. Compressibility factor
b. Thermal expansivity
c. Isothermal compressibility
d. Volume expansivity

A

c. Isothermal compressibility

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7
Q

The Carnot cycle is independent of the working substance

a. False
b. True given the substance remain ideal
c. True only for heat engines running on the Carnot cycle
d. Always true

A

d. Always true

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8
Q

Which equation is the correct expression for the compressor efficiency?

a. (Wisen-Ws)/ Wisen
b. (W-Ws)/Ws
c. Wisen/Ws
d. Ws/Wisen

A

c. Wisen/Ws

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9
Q

Which of the following statement is false regarding a reversible process?

a. It can be considered frictionless
b. It transverses a succession of equilibrium states
c. It can be reversed at any point by a differential
change in external conditions
d. It is driven by forces whose inbalance is finite in magnitude

A

c. It can be reversed at any point by a differential
change in external conditions

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10
Q

For a fluid at the two-phase region, the CEOS solution with the highest value corresponds to the

a. Liquid-liquid-like solution
b. Trivial solution
c. Critical solution
d. Vapor/vapor-like solution

A

d. Vapor/vapor-like solution

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11
Q

The thermal efficiency of a steam power plant is increased when

a. The pressure is increased in the boiler
b. The pressure is decreased in the boiler
c. The steam critical point is approached in the boiler
d. The vaporization temperature is reduced

A

a. The pressure is increased in the boiler

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12
Q

As a requirement, the choice of refrigerant must

a. Have a relatively high vapor pressure in the condenser to aid condensation
b. Have a vapor pressure lower than atmospheric at the evaporator temperature for easier compression
c. Have a vapor pressure greater than atmospheric at the evaporator temperature
d. Be able to attain below atmospheric pressure after the condenser to aid throttling

A

c. Have a vapor pressure greater than atmospheric at the evaporator temperature

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13
Q

The coefficient of performance for a Carnot refrigerator is independent of the type of refrigerants.

a. False
b. True
c. True only for a certain pressure range
d. True only for a specific operating temperature limit

A

b. True

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14
Q

The terms of the extended virial describe/factors in which of the following?

a. Compressibility parameters
b. None of these
c. Interaction parameters among atoms
d. Volume-dependent parameters

A

a. Compressibility parameters

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15
Q

For a mechanically reversible isothermal process, which of the following is true?

a. ΔU = 0
b. All of these
c. Q = -W
d. ΔH = 0

A

b. All of these

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16
Q

Which statement is true for State Functions

a. Does not depend on path nor history
b. Does not depend on the path but depends on the history of the substance
c. Depends on the path but not the history
d. Depends on both path and history

A

a. Does not depend on path nor history

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17
Q

Fluids having the same value of w, compared at the same Tr, and Pr, have about the same value of Zr.

a. True only for ideal gases
b. True only for simple gases
c. Always true
d. True only for noble gases

A

c. Always true

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18
Q

Which of the following statements is true about the alpha function of the equations of state?

a. A constant function for all EOS
b. It is an empirical value determined by experiments
c. It is temperature and substance dependent d. None of these statements is correct

A

a. A constant function for all EOS

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19
Q

A measure of the roundness of the atom/molecule of a substance

a. Acentric factor
b. Compressibility factor
c. Volume expansivity
d. Isothermal compressibility

A

a. Acentric factor

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20
Q

The maximum work obtained from an adiabatic turbine given an inlet condition and discharge pressure.

a. Expansive work
b. Adiabatic work
c. Isobaric work
d. Isentropic work

A

d. Isentropic work

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21
Q

For a closed system undergoing the same change for different processes

a. Q+W are different
b. Q+W is the same
c. Q is always the same
d. W is always same

A

b. Q+W is the same

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22
Q

The thermal efficiency of a steam power plant is increased when

a. The critical point is approached in the condenser
b. The temperature is reduced in the condenser
c. The temperature is lowered below that of the
cooling medium
d. The pressure is increased in the condenser

A

b. The temperature is reduced in the condenser

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23
Q

Any ideal engine operating between the two infinite reservoirs is a Carnot cycle

a. Only when the engine cycle is reversible
b. False
c. True
d. Only when the working substance is an ideal gas

A

a. Only when the engine cycle is reversible

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24
Q
  1. Which of the following is the least harmful in terms of ozone depletion

a. C CI3 F
b. C H Cl2 C F3
C. C F3 CH2 F
d. C Cl2 F2

A

C. C F3 CH2 F

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25
Q

Heat of reaction is a result of

a. Temperature difference of reactants and products
b. Changes in chemical nature of reactants and products
c. Changes in activation energy
d. Difference in molecular structure of reactant and product

A

d. Difference in molecular structure of reactant and product

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26
Q

Which of the following is not a step in the Carnot cycle

a. Adiabatic compression until the temperature rises from TC and TH
b. Adiabatic expansion until the temperature decreases to TC
c. Isothermal expansion with absorption of heat QH
d. Isothermal expansion with rejection of heat QC

A

d. Isothermal expansion with rejection of heat QC

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27
Q

The phase rule variables are

a. Can be both intensive and extensive
b. Intensive properties only
c. Extensive properties only
d. Cannot be defined without context

A

b. Intensive properties only

28
Q

For a pure substance, the heat of transition
accompanying phase change is a function of

a. Pressure only
b. Temperature only
c. Volume only
d. Internal energy only

A

b. Temperature only

29
Q

The maximum efficiency of a heat engine is achieved when

a. QC = QH
b. QC= 0
c. QH-QC = 0
d. QH = 0

A

b. QC= 0

30
Q

In general, the P-T relationship (and thus the other thermodynamic properties) of saturated steam is not a linear function as can be seen from the phase diagram for water. However, linear interpolation is allowed in the steam tables. Which statement justifies this observation?

a. Linearity is not a requirement for interpolation.
b. Steam is a special case fluid to which linearity is always a good estimate.
c. The properties in the steam table are transformed properties to fit a linear relation
d. Values are given in intervals close enough that linear interpolation is satisfactory.

A

c. The properties in the steam table are transformed properties to fit a linear relation

31
Q

The total quantity of energy is constant

a. False
b. True only for reversible processes
c. True only for closed, ideal systems
d. Always true

A

d. Always true

32
Q

The quality of a vapor-liquid system in equilibrium is defined as

a. Mole fraction of liquid
b. Mole fraction of vapor
c. Moles of vapor
d. Moles of liquid

A

b. Mole fraction of vapor

33
Q

Which of the following statements is true about the internal energy?

a. It is independent of pressure changes
b. It refers to the molecular energy of the substance excluding its macromolecular conditions c. It’s value is zero for ideal gases
d. It remains constant for mechanically reversible processes

A

d. It remains constant for mechanically reversible processes

34
Q

The international treaty which called for the phasing out of production of numerous refrigerants responsibly for the ozone depletion

a. Montreal Protocol
b. Geneva convention
c. Kyoto Protocol
d. Gothenburg Protocol

A

a. Montreal Protocol

35
Q

The final temperature and pressure for a given volume where the meniscus of a liquid remains
distinguishable

a. Critical point
b. Sub-critical point
c. Saturated T and P
d. Triple Point

A

d. Triple Point

36
Q

In a flow process, SG = 0

a. When the flowing substance is ideal gas
b. When the heat reservoirs are finite
c. When heat transfer to the surrounding is zero
d. When the process is completely reversible

A

d. When the process is completely reversible

37
Q

Which of the following is true regarding refrigeration effect per unit of work?

a. Decreases as TH and TC increases
b. Decreases as TH increases and TC decreases
c. Increases as TH increases and TC decreases
d. Increases as TH and TC increases

A

b. Decreases as TH increases and TC decreases

38
Q

One difficulty of achieving a steam power plant based on the Carnot cycle is the requirement for a pump that takes in a mixture of liquid and vapor. This poses problem because bubbles in pumps promote a destructive condition called

a. Infraction
b. Sonic upsurge
c. Cavitation
d. Pitting corrosion

A

c. Cavitation

39
Q

Consider a closed system consisting of a 3- component mixture in a vapor-liquid equilibrium. According to the phase rule, how many degrees of freedom does the system have?

a. 2
b. 3
c. 1
d. 4

A

a. 2

40
Q

Which of the following is true regarding the entropy change of a system?

a. None of the above
b. Always equal to zero or positive
c. Can be negative
d. Always greater than 0

A

b. Always equal to zero or positive

41
Q

The virial coefficients are known functions of

a. Nature of the substance and temperature
b. Nature of substance and pressure
c. Volume and pressure
d. Temperature and volume

A

a. Nature of the substance and temperature

42
Q

The heat capacity of a gas mixture is

a. Independent of temperature
b. A function of individual heat capacities of the components
c. Independent of mole fractions of the components
d. A function of partial pressures of the components

A

b. A function of individual heat capacities of the components

43
Q

A turbine converts __________ of a high velocity steam into __________, which in turn is converted to __________ by the moving parts.

a. Potential energy, internal energy, kinetic energy
b. Internal energy, kinetic energy, shaft work
c. Kinetic energy, potential energy, shaft work
d. Internal energy, potential energy, kinetic energy

A

b. Internal energy, kinetic energy, shaft work

44
Q

It relates the latent heat of a substance to other intensive PVT properties.

a. Clausius-Clapeyron equation
b. Gibb’s equation
c. Trouton’s rule
d. Phase rule

A

a. Clausius-Clapeyron equation

45
Q

At the critical point, Cubic Equations of State have

a. 3 solutions, all imaginary
b. 3 solutions, 1 for vapor, 1 for liquid, 1 without meaning
c. 3 solutions, 1 imaginary
d. 3 solutions, 1 value

A

d. 3 solutions, 1 value

46
Q

A family of mathematical models which predicts the PVT behavior of fluids

a. Maxwell equations
b. Fundamental property relations
c. Continuity equation
d. Equations of state

A

b. Fundamental property relations

47
Q

Given the diagram below, which process produces and requires work, respectively?

a. 2 to 3, 1 to 4
b. 1 to 4, 2 to 3
c. 1 to 2, 3 to 4
d. 3 to 4, 1 to 2

A

a. 2 to 3, 1 to 4

48
Q

The thermal efficiency of a steam power plant is increased when

a. The temperature is lowered below that of the cooling medium
b. The temperature is reduced in the condenser
c. The pressure is increased in the condenser
d. The critical point is approached in the condenser

A

b. The temperature is reduced in the condenser

49
Q

It is the additional work that can be recovered if irreversibilities are eliminated

a. Ideal work
b. Lost work
c. Ideal work
d. Shaft work

A

b. Lost work

50
Q

For a closed system undergoing the same change for different processes

a. Q+W is the same
b. Q + W is different
c. Q is always the same
d. W is always the same

A

a. Q+W is the same

51
Q

The terms of the extended virial equations describe/factors in which of the following?

a. Volume-dependent parameters
b. Compressibility parameters
c. None of these
d. Interaction parameter among atoms

A

b. Compressibility parameters

52
Q

Which of the following is true regarding the heat capacities for an ideal gas?

a. Cp is constant, Cv is temperature dependent
b. Cp and Cv are both constant
c. Cp and Cv, are temperature dependent
d. Cv is constant, Cp is temperature dependent

A

c. Cp and Cv, are temperature dependent

53
Q

Heat and work can be converted interchangeable with approaching to 100% efficiency

a. False
b. True
c. True only if friction is eliminated
d. False only for real substances

A

c. True only if friction is eliminated

54
Q

The thermal efficiency of a steam power plant is increased when

a. The temperature is lowered below that of the
cooling medium
b. The critical point is approached in the condenser
c. The pressure is increased in the condenser
d. The temperature is reduced in the condenser

A

d. The temperature is reduced in the condenser

55
Q

For two reservoirs operating at TH and TC, the total entropy change

a. Exponentially decreases as TH-TC decreases
b. Decreases as TH- TC decreases
c. Exponentially increases as TH-TC decreases
d. Increases as TH-TC decreases

A

b. Decreases as TH- TC decreases

56
Q

The coefficient of performance for a Carnot refrigerator is independent of the type of refrigerants

a. True
b. True only for a certain pressure change
c. True only for a specific operating temperature limit
d. False

A

a. True

57
Q

For a mechanically reversible adiabatic process, which of the following is true?

a. W = CvΔT
b. W = Q
c. W = 0
d. W = CpΔT

A

a. W = CvΔT

58
Q

For water at the triple point, how many degrees of freedom does the system has?

A

zero

59
Q

Heats of reaction is a result of

A

characterized by the temperature changes during chemical reactions. It lies in the difference between the molecular configurations of products and reactants.

60
Q

Compared to other engines, the thermal efficiency of a Carnot engine is

A

Possible answers: (1) Its efficiency depends only on the temperature levels and not upon the working substance of the engine

(2) For two given heat reservoirs, no engine can have a thermal efficiency higher than that Carnot engine.

61
Q

The phase change enthalpy, ΔHv, is proportional to the slope of InPsat vs 1/T plot. This relationship is given by

A

Clausius Equation

62
Q

All ideal gases have the same molar volume.

a. Only for pure species
b. Only for pure species and mixtures but not solutions
c. Only at the same T and P
d. Only within a narrow temperature range.

A

c. Only at the same T and P

63
Q

For a refrigerator operating between given values of TH and TC, the maximum possible coefficient of performance is given by

a. Carnot refrigerator
b. Vapor-compression refrigerator
c. Vapor-absorption refrigerator
d. Rankine refrigerator

A

a. Carnot refrigerator

64
Q

Which of the following sequences correctly outlines a vapor-compression cycle

a. 1. Liquid evaporation at constant P
2. Isentropic compression to higher P
3. Cooling and condensation with generation of
heat
4. Expansion by throttling

b. 1. Liquid evaporation at constant P
2. Isentropic throttling to lower P
3. Condensation with rejection of heat
4. Isentropic compression to original P

c. 1. Isentropic evaporation at constant P
2. Compression to higher P with increase in S
3. Condensation with rejection of heat at
decreasing P
4. Further expansion by throttling

d. None of these are correct

A

a. 1. Liquid evaporation at constant P
2. Isentropic compression to higher P
3. Cooling and condensation with generation of
heat
4. Expansion by throttling

65
Q

The partial properties making up a solution are not independent of one another. This statement takes mathematical form in

a. Summability relation
b. Gibbs/Duhem equation
c. Lewis/Randall rule
d. Fundamental property relation

A

b. Gibbs/Duhem equation

THERMODYNAMICS (2 decks)

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