Deck 18: Chemical Thermodynamics

Question 1

If a piston of cross-sectional area 1.60×10² mm² exerts a pressure of 4.80×10⁵ N/m², by what distance should it move in order to perform 1.92×10² J of work?

A) 5.00 m
B) 7.50 m
C) 2.50 m
D) 12.5 m
E) 10.0 m

Answer 1

2.50 m

Question 2

Which of the following best defines a state function?

A) It is the property of a system whose magnitude depends on the pathway used to go from one state to another.
B) It is the property of a system whose magnitude depends on only the present state of the system, not its previous history.
C) It is the property of a system whose magnitude depends on the work done in the past and on how the equilibrium state is reached.
D) It is the property of a system whose magnitude depends on only the previous history of the system.
E) It is the property of a system whose magnitude is independent of the equilibrium state of the system.

Answer 2

It is the property of a system whose magnitude depends on only the present state of the system, not its previous history.

Question 3

If a piston exerts an external pressure of 3.20×10⁵ N/m² to move a distance of 3.50 m, what is the area of cross-section of the piston? Given: Work done by the piston = 1.50×10² J.

A) 134 mm²
B) 175 mm²
C) 224 mm²
D) 115 mm²
E) 252 mm²

Answer 3

134 mm²

Question 4

If the external pressure on the piston is less than the internal pressure in the piston, then the ideal gas in the piston will be compressed, and the surroundings will perform work on the system.

Question 5

If a piston of cross-sectional area 2.50×10² mm² exerts an external pressure of 4.00×10⁴ N/m², what is the force acting on the piston?

A) 25.0 N
B) 4.25 N
C) 17.5 N
D) 10.0 N
E) 32.5 N

Question 6

If a piston exerts an external pressure of 75.0×10³ N/m² and moves a distance of 2.00 m, what is the magnitude of the work performed by the piston? Given: Cross-sectional area of the piston = 5.00×10² mm².

A) 7.50×10¹ J
B) 15.0×10¹ J
C) 22.5×10¹ J
D) 37.5×10¹ J
E) 50.0×10¹ J

Question 7

Internal energy is a state function.

Question 8

If a force of 250 N acts on a piston of surface area 5.0×10² mm², what is the external pressure exerted by the piston?

A) 6.5×10⁴ N/m²
B) 1.0×10⁵N/m²
C) 5.0×10⁵ N/m²
D) 2.5×10⁴ N/m²
E) 9.5×10⁵ N/m²

Question 9

_____ is the study of the interrelationships among heat, work, and the energy content of a system at equilibrium.

Question 10

If a force of 80.0 N acts on the piston, by what distance should the piston move in order to perform 5.00×10² J of work?

A) 6.25 m
B) 11.5 m
C) 2.48 m
D) 14.9 m
E) 17.5 m

Question 11

Which of the following is used to calculate the magnitude of the work performed by the piston?

A) $\frac { \mathrm { P } _ { \mathrm { ext } } \mathrm { A } } { \Delta \mathrm { h } }$
B) $\frac { P _ { \text {ext } } \Delta h } { A }$
C) $\mathrm { P } _ { \mathrm { ext } } \mathrm { A } \Delta \mathrm { h }$
D) $P _ { e x t} A$
E) $\mathrm { P } _ { \mathrm { ext } } \Delta \mathrm { h }$

Question 12

Work done by a system on its surroundings has a positive sign because it results in a transfer of energy to a system from its surroundings.

Question 13

If a piston performs 64.8 J of work and exerts an external pressure of 87.5 N/m², what is the change in volume of the cylinder?

A) 0.741 m³
B) 1.45 m³
C) 0.267 m³
D) 1.86 m³
E) 2.50 m³

Question 14

In the SI system, the units of work and heat are _____.

A) celsius
B) pascal
C) newton
D) joules
E) kelvin

Question 15

A small high-performance internal combustion engine has six cylinders with a total nominal displacement (volume) of 3.60 L and a 10:1 compression ratio. How much work in joules is done when a gas in one cylinder of the engine expands at constant temperature against an opposing pressure of 60.0 atm during the engine cycle? Assume that the gas is ideal, the piston is frictionless, and no energy is lost as heat.

A) 1.32×10³ J
B) -3.28×10³ J
C) 7.84×10³ J
D) -7.84×10³ J
E) 3.28×10³ J

Question 16

If a force of 120 N acts through a distance of 6.0 m, what is the work done by the system?

A) 240 J
B) 420 J
C) 180 J
D) 360 J
E) 720 J

Question 17

A closed system can exchange matter with its surroundings.

Question 18

A(n) _____ is that part of the universe in which we are interested, such as a mixture of gases in a glass bulb or a solution of substances in a flask.

Question 19

Explain the concept of a state function.

Question 20

If a piston exerts an external pressure of 60 N/m² and the change in volume of the cylinder is 0.75 m³, what is the magnitude of the work performed by the piston?

A) 90 J
B) 60 J
C) 25 J
D) 80 J
E) 45 J

Question 21

The molar enthalpy of fusion for ice at 0.0°C and a pressure of 1.00 atm is 8.52 kJ, and the molar volumes of ice and water at 0°C are 0.0286 L and 0.0220 L, respectively. What is the change in internal energy for the melting of ice at $0.0 ^ { \circ } \mathrm { C }$ if the pressure is kept constant?

A) 2.35 kJ
B) 8.52 kJ
C) 11.5 kJ
D) 5.17 kJ
E) 15.8 kJ

Question 22

The combustion of graphite to produce carbon dioxide is described by the equation C (graphite, s) + O₂(g) → CO₂(g). At 286.0 K and 1.000 atm, ΔH = −367.6 kJ/mol of graphite for this reaction, and the molar volume of graphite is 7.900× 10 ^-3 L. What is ΔE for the reaction?

A) -465.8 kJ/mol
B) -227.3 kJ/mol
C) 465.8 kJ/mol
D) -367.6 kJ/mol
E) 227.3 kJ/mol

Question 23

When a reaction involves only solids, liquids, or liquid solutions, the change in enthalpy is equal to the change in internal energy.

Question 24

At constant temperature, the change in internal energy $( \Delta \mathrm { E } )$ is equal to _____.

A) $\Delta \mathrm { H } - \mathrm { RT } \Delta { \mathrm { n } }$
B) $\Delta \mathrm { H } + \mathrm { RT } \Delta \mathrm { n }$
C) $\Delta \mathrm { H } \Delta n + \mathrm { RT }$
D) $\Delta \mathrm { H } \Delta n - \mathrm { R T}$
E) $\mathrm { RT } \Delta { n } - \Delta \mathrm { H }$

Question 25

The change in enthalpy ( $\Delta H$ ) of a system is equal to _____.

A) $\frac { \Delta \mathrm { E } } { \Delta ( \mathrm { PV } ) }$
B) $\triangle E + \Delta ( P V )$
C) $\frac { \Delta ( \mathrm { PV } ) } { \Delta \mathrm { E } }$
D) $\Delta \mathrm { E } - \Delta ( \mathrm { PV } )$
E) $\Delta ( \mathrm { PV } ) - \Delta \mathrm { E }$

Question 26

If 120 J of work is done by the system and its change in internal energy is 480 J, what is the amount of heat transferred between the system and its surroundings?

A) 600 J
B) 360 J
C) 4.00 J
D) 480 J
E) 5.76×10⁴ J

Question 27

State and explain the first law of thermodynamics.

Question 28

_____ is a state function that is the sum of the system's internal energy and the product of its pressure and volume.

Question 29

For endothermic reactions that result in a net consumption of gas, $\Delta E < \Delta H$ .

Question 30

A sample of an ideal gas in the cylinder of an engine is compressed from 400.0 mL to 200.0 mL during the compression stroke against a constant pressure of 10.00 atm. The total change in internal energy of the system is equal to -390.0 J. What is the amount of energy that is transferred from the gas to the surroundings as heat?

A) 202.6 J
B) 390.0 J
C) 98.34 J
D) 502.5 J
E) 187.4 J

Question 31

Derive the relationship between ΔH and ΔE.

Question 32

All systems have the tendency to move toward the lowest possible overall energy state.

Question 33

The greater the number of atoms or molecules in the gas, the greater the disorder.

Question 34

If "q" is the heat transferred and "w" is the work done, the change in the internal energy is equal to _____.

A) q+w
B) q×w
C) $\frac { \mathrm { q } } { \mathrm { w } }$
D) $w - q$
E) $q - w$

Question 35

If 3.00×10² J of work is done by the system and 1.50×10² J of energy is transferred between the system and its surroundings, what is the change in the internal energy of the system?

A) 3.00×10² J
B) 1.50×10² J
C) 4.50×10² J
D) 2.00×10² J
E) 6.00×10² J

Question 36

The lesser the number of microstates, the greater the entropy.

Question 37

The _____ of a system is the sum of the potential energy and the kinetic energy of all the components.

Question 38

In the equation, $\Delta \mathrm { E } _ { \mathrm { sys } } = \mathrm { q } + \mathrm { w }$ , q and w are state functions.

Question 39

The _____ states that the energy of the universe is constant.

Question 40

A sample of an ideal gas in the cylinder of an engine is compressed from 5.00×10² mL to 1.50×10² mL during the compression stroke against a constant pressure of 6.00 atm. At the same time, 1.80×10³ J of energy is transferred from the gas to the surroundings as heat. What is the total change in the internal energy of the gas in joules?

A) 67.5 J
B) 11.9 J
C) 32.8 J
D) 53.5 J
E) 78.4 J

Question 41

If the quantity of heat transferred is equal to 3.40 kJ and the absolute temperature of the object is $25.0 ^ { \circ } \mathrm { C }$ , what is the change in entropy for the process?

A) 15.7 J/K
B) 6.80 J/K
C) 2.39 J/K
D) 11.4 J/K
E) 9.82 J/K

Question 42

What is the ?S° for the reaction of liquid cyclohexane (C₆H₁₂) with O₂(g) to give CO₂(g) and H₂O(g) at 298 K? Given: S° for C₆H₁₂ = 204.4 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$ , S° for O₂ = 205.2 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$ , S° for CO₂ = 213.8 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$ , and S° for H₂O(g) = 188.8 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$ .

A) 550.6 J/K
B) 276.4 J/K
C) 364.4 J/K
D) 487.5 J/K
E) 762.8 J/K

Question 43

Which of the following causes an increase in the entropy of the system?

A) Decrease in the number of microstates
B) Condensation of vapor to form a liquid
C) Formation of a crystalline solid
D) Freezing of water to form ice
E) Expansion of gas into a vacuum

Question 44

Work done in an irreversible process is always equal to or greater than work done in a corresponding reversible process.

Question 45

If the enthalpy of fusion of ice is 6.01 kJ/mol, what is the entropy of fusion of ice?

A) 11.3 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$

B) 6.75 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$
C) 22.0 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$
D) 17.2 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$
E) 29.6 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$

Question 46

A(n) _____ process is one in which the intermediate states are not equilibrium states, so change occurs spontaneously in only one direction.

Question 47

What are the differences between a reversible and an irreversible process?

Question 48

Thermodynamic properties, such as internal energy and enthalpy are evaluated in absolute terms.

Question 49

If the change in entropy of CO₂ is 16.8 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$ and its temperature changes from 298 K to 318 K, how many moles of CO₂ are present? Given: C_p of CO₂ = 36.94 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$ .

A) 2 moles
B) 3 moles
C) 5 moles
D) 7 moles
E) 10 moles

Question 50

A disordered system has higher entropy than an ordered system.

Question 51

The process of condensing a vapor to form a liquid must be accompanied by an increase in the entropy of the system.

Question 52

The _____ states that the entropy of the universe remains constant in a reversible process, whereas the entropy of the universe increases in an irreversible process.

Question 53

If the change in entropy of the system is equal to 5.8 J/K and the absolute temperature of the system is 290 K, what is the change in internal energy of the system? Given: Work done by the system is equal to 1.3 kJ.

A) 4.8 kJ
B) 7.2 kJ
C) 2.9 kJ
D) 16 kJ
E) 12 kJ

Question 54

_____ is the thermodynamic property of all substances that is proportional to their degree of disorder.

Question 55

A(n) _____ process is one in which every intermediate state between the extremes is an equilibrium state, regardless of the direction of the change.

Question 56

The absolute entropy of a substance tends to decrease with increasing molecular complexity.

Question 57

If the temperature of 10 moles of oxygen changes from 298 K to 310 K, what is the change in entropy for oxygen? Given: C_p of oxygen = 29.38 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$

A) 11.6 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$
B) 4.67 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$
C) 15.8 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$
D) 8.32 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$
E) 19.7 $\mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } )$

Question 58

ΔE for a process is the same whether that process is carried out in a reversible manner or an irreversible one.

Question 59

If the change in entropy of the system is equal to 4.70 J/K and the absolute temperature of the object is 287K, what is the quantity of heat transferred from the object?

A) 4.56 kJ
B) 1.35 kJ
C) 8.76 kJ
D) 12.5 kJ
E) 15.8 kJ

Question 60

Soft crystalline substances have higher entropies because of increased molecular motion and disorder.

Question 61

Explain standard free-energy change and standard free energy of formation.

Question 62

If the ΔG_f° of benzene is equal to 124.5 kJ/mol and the ΔG_f° of cyclohexane is equal to 217.3 kJ/mol, what is the ΔG° for the reaction of benzene with hydrogen gas to give cyclohexane?

A) -124.6 kJ
B) 186.5 kJ
C) - 75.9 kJ
D) 92.8 kJ
E) 57.3 kJ

Question 63

The magnitude of the equilibrium constant is directly influenced by the tendency of a system to move toward maximum disorder and seek the lowest energy state possible.

Question 64

The _____ is the change in free energy when one substance or a set of substances in their standard states is converted to one or more other substances, also in their standard states.

Question 65

In the absence of a phase change, neither ΔH nor ΔS vary greatly with temperature.

Question 66

At constant temperature and pressure, the change in Gibbs free energy $( \Delta \mathrm { G } )$ is equal to _____.

A) $\mathrm { T } \Delta \mathrm { S } - \Delta \mathrm { H }$
B) $\mathrm { T } \Delta \mathrm { H } - \Delta \mathrm { S }$
C) $\Delta \mathrm { H} \Delta{S } - \mathrm { T }$
D) $\Delta \mathrm { H } + \mathrm { T } \Delta \mathrm { S }$
E) $\triangle \mathrm { H } - \mathrm { T } \Delta \mathrm { S }$

Question 67

The _____ states that the entropy of any perfectly ordered, crystalline substance at absolute zero is zero.

Question 68

The _____ is the amount of heat needed to raise the temperature of 1 mol of a substance by 1°C at constant pressure.

Question 69

If ΔS_univ < 0 for a process or a reaction, the process will occur spontaneously.

Question 70

What is the ?G at $350.0 ^ { \circ } \mathrm { C }$ for the reaction $\mathrm { N } _ { 2 } ( g ) + 3 \mathrm { H } _ { 2 } ( g ) f \quad 2 \mathrm { NH } _ { 3 } ( g )$ assuming that ?H and ?S do not change between 25.00°C and 350.0°C?Given: S°(N₂) = 191.6 J/(mol·K), S°(H₂) = 130.7 J/(mol·K), S°(NH₃) = 192.8 J/(mol·K), and ?H_f° (NH₃) = ?45.90 kJ/mol.

A) 156.5 kJ/mol
B) 31.62 kJ/mol
C) -93.45 kJ/mol
D) 114.6 kJ/mol
E) - 168.8 kJ/mol

Question 71

If Q > K, then the reaction proceeds spontaneously to the right as written, resulting in the net conversion of reactants to products.

Question 72

The entropy of the universe increases during all processes that produce energy.

Question 73

Explain the third law of thermodynamics.

Question 74

The entropy of 1 mol of a substance at a standard temperature of 298 K is its _____.

Question 75

A positive ΔG° means that the equilibrium constant is greater than 1.

Question 76

The _____ of a compound is the change in free energy that occurs when 1 mol of a substance in its standard state is formed from the component elements in their standard states.

Question 77

The temperature at which liquid water is in equilibrium with water vapor is called the _____ of water.

Question 78

At 25°C, for the reaction $2 \mathrm { H } _ { 2 } ( \mathrm {~g} ) + \mathrm { O } _ { 2 } ( \mathrm {~g} ) f \quad 2 \mathrm { H } _ { 2 } \mathrm { O } ( \mathrm { l } )$ , the standard enthalpy change (?H°) is ?285.8 kJ/mol, and the absolute entropies of the products and reactants are S°(H₂O) = 70.00 J/(mol·K), S°(O₂) = 205.2 J/(mol·K), and S°(H₂) = 130.7 J/(mol·K). What is the standard free-energy change for the reaction?

A) 278.6 kJ/mol
B) -188.4 kJ/mol
C) -249.7 kJ/mol
D) 359.8 kJ/mol
E) -313.4 kJ/mol

Question 79

For a spontaneous process under standard conditions, K_eq and K_p are greater than 1.

Question 80

At temperatures greater than 373.15 K, ΔG is negative, and water evaporates spontaneously and irreversibly.