Deck 12: Thermodynamics Why Chemical Reactions Happen

Question 1

The molar entropy of ammonia, NH₃g), at 25 $\degree$ C is 192.5 J/mol .K.Estimate the number of microstates accessible to a NH₃ molecule at 25 $\degree$ C to two significant figures.

A)1.1 * 10¹⁰
B)1.4 *10²⁵
C)6.8 * 10³³
D)4.0 * 10⁸³
E)23

Answer 1

1.1 * 10¹⁰

Question 2

Of the three modes of molecular motion-vibration, rotation, and translation-which requires the greatest amount of energy to cause an excitation from the ground state to the first excited state?

A)vibration
B)rotation
C)translation
D)They all require the same amount of energy.
E)none, as quantized energy states do not apply to these motions

Answer 2

vibration

Question 3

When the volume of a gas is increased, the energy separation between microstates

A)increases.
B)decreases.
C)remains unchanged.
D)becomes infinite.
E)disappears.

Answer 3

decreases.

Question 4

Which of the following processes is NOT spontaneous?

A)Iron in moist air rusts.
B)Carbon dioxide and water react to form sugar and oxygen gas.
C)Liquid water in a freezer turns to ice.
D)A spark ignites a mixture of propane and air.
E)Baking soda sodium hydrogen carbonate) reacts with lemon juice dilute citric acid).

Question 5

Which of the following is the best definition of a microstate as it pertains to entropy on the molecular level?

A)the state solid, liquid, or gas) of a small cluster of atoms or molecules
B)a property of a small cluster of atoms and molecules, such as temperature, that is independent of how the property was achieved
C)the set of vibrational, rotational, and translational energy levels in a system
D)a unique specification of the vibrational, rotational, and translational states of a single molecule in a system
E)a unique specification of the vibrational, rotational, and translational states of all the particles in a system

Question 6

Which of the following statements regarding spontaneous processes is NOT true?

A)Spontaneous processes are exothermic.
B)Spontaneous processes proceed without outside intervention once initiated.
C)Spontaneous reactions are not always rapid.
D)The motional freedom of particles tends to increase during spontaneous change.
E)Particles tend to become more spread out during spontaneous change.

Question 7

At 0 K, the entropy of a perfect crystal is

A)( $\gt$ 0)
B)(= 0)
C)( $\lt$ 0)
D)( $\gt$ 0, = 0, or $\lt$ 0, depending on the chemical structure of the crystal)
E)( $\gt$ 0 or = 0, depending on the chemical structure of the crystal)

Question 8

Which of the following must be true for the microstates of a system? I.The energy of each microstate equals the energy of the system.
II)The entropy of each microstate equals the entropy of the system.
III)The number of microstates equals the entropy of the system.

A)I only
B)II only
C)III only
D)I and III only
E)I, II, and III are all true

Question 9

At 25 $\degree$ C, a benzene molecule (C₆H₆) has approximately 1.143 * 10¹⁴ accessible microstates.Estimate the molar entropy of C₆H₆ at 25.0 $\degree$ C to two significant figures.

A)4.5 *10^-22 J/mol . K
B)3.9 J/mol . K
C)14 J/mol . K
D)32 J/mol . K
E)2.7 * 10² J/mol . K

Question 10

How many microstates are accessible to one mole of atoms in a perfect crystalline lattice at absolute zero?

A)0
B)1
C)1.381 * 10^-23
D)52.64
E)6.022 * 10²³

Question 11

Given one mole of each of the following, which of the following has the highest number of accessible microstates?

A)Ice, H₂Os), at 273 K
B)Liquid water, H₂Ol), at 373 K
C)Steam, H₂Og), at 373 K
D)Propane, CH₃CH₂CH₃g), at 373 K
E)Butane, CH₃CH₂CH₂CH₃g), at 373 K

Question 12

Which of the following states of motion has the highest number of occupied excited states at room temperature-rotational, vibrational, or translational?

A)rotational
B)vibrational
C)translational
D)The number of occupied excited states is the same for the three modes of motion.
E)none of these, as excited states do not apply to these motions

Question 13

Which of the following statements is a valid definition of entropy?

A)It is a measure of the average kinetic energies of the particles in a system.
B)It is a measure of the enthalpy changes during a spontaneous change.
C)It is a measure of how the temperature changes during a spontaneous change.
D)It is a measure of how randomly arranged the particles in a system are.
E)It is a measure of how dispersed the energy of a system is.

Question 14

What modes of motion does a molecule of chlorine have?

A)translational, rotational, and vibrational
B)kinetic energy and potential energy
C)microstate and macrostate
D)Boltzmann and non-Boltzmann
E)all of the above

Question 15

According to the second law of thermodynamics, the entropy change in an isolated system ( $\Delta$ S_sys) during a spontaneous process must be

A)greater than zero.
B)less than zero.
C)equal to zero.
D)greater than or equal to zero.
E)greater than, less than, or equal to zero.

Question 16

An oxygen molecule at room temperature can access the largest number of accessible microstates associated with which mode of molecular motion?

A)vibrational
B)kinetic
C)translational
D)elastic
E)Boltzmann

Question 17

Boltzmann derived the relationship S = k ln W, where W is the

A)number of microstates.
B)vibrational energy.
C)kinetic energy.
D)Wentworth factor.
E)potential energy.

Question 18

Which of the following is a driving force behind spontaneous reactions?

A)A solid is formed.
B)Heat is absorbed.
C)The reaction is rapid.
D)The motional freedom of the particles increases.
E)The enthalpy of the particles increases.

Question 19

The entropy change in a system ( $\Delta$ S_sys) during a spontaneous process must be

A)greater than zero.
B)less than zero.
C)equal to zero.
D)greater than or equal to zero.
E)greater than, less than, or equal to zero.

Question 20

Perfect crystals of carbon monoxide (CO) are difficult to prepare because the very small dipole moment allows a few molecules to align in a pattern like CO OC CO instead of CO CO CO.If such crystals were cooled to 0 K, what would be the value of their absolute entropy?

A)( $\gt$ 0)
B)(= 0)
C)( $\lt$ 0)
D)( $\gt$ 0, = 0, or $\lt$ 0, depending on how carefully it was cooled)
E)( $\gt$ 0 or = 0, depending on how carefully it was cooled)

Question 21

The absolute entropy of an NaCl crystal is

A)an intensive property and a state function.
B)an intensive property and a path function.
C)an extensive property and a state function.
D)an extensive property and a path function.
E)not appropriately described in terms of an intensive property, an extensive property, a state function, or a path function.

Question 22

Consider a closed container containing a 1.00 M solution of aqueous HCl at 298 K.Above the solution, air containing both water vapor and HCl gas at their equilibrium vapor pressures exerts a total pressure of 1.00 bar.Which of the following is/are in their thermodynamic standard state? I.the liquid water
II)the HCl solution
III)the water vapor

A)I only
B)II only
C)III only
D)I and II only
E)I, II, and III are all in their standard state.

Question 23

Which of the following are listed in order of increasing standard molar entropy?

A)Au(s) $\lt$ Au(g) $\lt$ H₂O(l) $\lt$ CH₃OH(l) $\lt$ H₂O(g)
B)Au(s) $\lt$ H₂O(l) $\lt$ CH₃OH(l) $\lt$ Au(g) $\lt$ H₂O(g)
C)Au(s) $\lt$ H₂O(l) $\lt$ CH₃OH(l) $\lt$ H₂O(g) $\lt$ Au(g)
D)H₂O(l) $\lt$ CH₃OH(l) $\lt$ Au(s) $\lt$ Au(g) $\lt$ H₂O(g)
E)H₂O(l) $\lt$ Au(s) $\lt$ CH₃OH(l) $\lt$ H₂O(g) $\lt$ Au(g)

Question 24

In a spontaneous process, the entropy of the universe

A)always increases.
B)always decreases.
C)does not change.
D)may decrease if the entropy of the system decreases sufficiently.
E)may decrease if the entropy of the system increases sufficiently.

Question 25

Which of the following is in the correct order of standard state entropy? I.NaCl(aq) $\lt$ NaCl(s)
II.O₂(g) $\lt$ O₃(g)
III.Kr(g) $\lt$ Cl₂(g)

A)I only
B)II only
C)III only
D)I and II only
E)II and III only

Question 26

During a spontaneous chemical reaction, it is found that $\Delta$ S_sys is less than 0.This means that

A)( $\Delta$ S_surr is less than 0 and its magnitude is less than $\Delta$ S_sys.)
B)( $\Delta$ S_surr is less than 0 and its magnitude is greater than $\Delta$ S_sys.)
C)( $\Delta$ S_surr is greater than 0 and its magnitude is less than $\Delta$ S_sys.)
D)( $\Delta$ S_surr is greater than 0 and its magnitude is greater than $\Delta$ S_sys.)
E)an error has been made, as S_sys is greater than 0 by necessity for a spontaneous process.

Question 27

Which of the following statements regarding absolute and standard entropies is NOT true?

A)The standard entropy of a solution is the value of S when the solution is at 298 K and 1 M concentration.
B)The standard entropy of a gas is the value of S when the gas is at 298 K and 1 bar pressure.
C)The standard entropy of a pure solid or liquid is the value of S for its most stable allotrope at 298 K and 1 bar.
D)Elements in their standard states at 298 K and 1 bar have nonzero entropy values.
E)The entropy of a compound increases linearly with temperature.

Question 28

The standard molar entropy of lead(II) bromide (PbBr₂) is 161 J/mol .K.What is the entropy of 2.45 g of PbBr₂?

A)(F+1.07 J/K)
B)(-1.07 J/K)
C)(+161 J/K)
D)(-161 J/K)
E)0 J/K

Question 29

Which of the following is in the correct order of standard state entropy? I.Diamond $\lt$ graphite
II.Liquid water $\lt$ solid water
III.NH₃ $\lt$ H₂

A)I only
B)II only
C)III only
D)I and II only
E)I and III only

Question 30

Which of the following processes is predicted to decrease the entropy of a system?

A)The number of particles increases.
B)Temperature increases.
C)Volume increases.
D)Pressure increases.
E)All of these increase the entropy of the system.

Question 31

Which of the following will have the greatest standard molar entropy (S $\degree$ )?

A)Cl₂(g)
B)Ne(g)
C)Na(s)
D)CH₃OH(l)
E)Na₂CO₃(s)

Question 32

The molar entropies of carbon monoxide and carbon dioxide at 25 $\degree$ C are 197.7 and 213.8 J/mol . K, respectively.How many times more accessible microstates does CO₂ have than CO at 25 $\degree$ C?

A)roughly 16 times more
B)roughly 1.1 times more
C)roughly 1.3 * 10¹¹ times more
D)roughly 6.9 times more
E)roughly 1.9 times more

Question 33

Indicate which of the following has the highest entropy at 298 K.

A)0.5 g of CO₂
B)1 mol of CO₂
C)2 kg of CO₂
D)2 mol of CO₂
E)All of the above have the same entropy at 298 K.

Question 34

According to the second law of thermodynamics, the change in the entropy of the universe ( $\Delta$ S_univ) during a spontaneous reaction is

A)zero.
B)negative.
C)positive.
D)less than the change in entropy of the system ( $\Delta$ S_sys).
E)greater than the change in entropy of the system ( $\Delta$ S_sys).

Question 35

If a reaction is spontaneous under a given set of conditions,

A)( $\Delta$ S_surr is greater than 0 for the reverse reaction.)
B)the reverse reaction is nonspontaneous.
C)( $\Delta$ S_sys for the reverse reaction is smaller than $\Delta$ S_sys for the forward reaction.)
D)the reverse reaction is also spontaneous.
E)(S_univ is greater than 0 for the reverse reaction.)

Question 36

In a spontaneous process, which of the following always increases?

A)the entropy of the system
B)the entropy of the surroundings
C)the entropy of the universe
D)the entropy of the system and the universe
E)the entropy of the system, surroundings, and universe

Question 37

During which of the following processes does the entropy of the system decrease?

A)Salt crystals dissolve in water.
B)Air escapes from a hole in a balloon.
C)Iron and oxygen gas react to form rust.
D)Ice melts in your hand.
E)None of these decrease the entropy of the system.

Question 38

During which of the following processes does the entropy of the system increase?

A)Water vapor condenses on a cool surface.
B)Helium gas escapes from a hole in a balloon.
C)Calcium carbonate stalactites form in a cave.
D)Water freezes in a freezer.
E)All of these increase entropy of the system.

Question 39

When carbon monoxide forms a crystal, each molecule can be pictured as having two possible orientations, CO or OC, because the molecular dipole moment is quite small.Assuming two possible microstates for each CO molecule, calculate the value of S when one mole of CO forms a crystalline solid at 0 K.

A)0 J/mol . K
B)2.00 J/mol .Kl
C)5.76 J/mol . K
D)9.57 * 10^-23 J/mol . K
E)The value of S is too small to calculate.

Question 40

Indicate which of the following has the lowest standard molar entropy (S $\degree$ ).

A)CH₄(g)
B)CH₃CH₂OH(l)
C)H₂O(s)
D)Na(s)
E)He(g)

Question 41

The enthalpy and entropy of vaporization of ammonia at its normal boiling point, -33.34 $\degree$ C, are approximately 23.35 kJ/mol and 97.4 J/mol . K, respectively.What would the entropy change of the universe be if one mole of ammonia vapor were to condense in a large room maintained at 30.0 $\degree$ C?

A)(+20.4 J/K)
B)(+77.0 J/K)
C)(-174.4 J/K)
D)(-20.4 J/K)
E)(+174.4 J/K)

Question 42

Which of the following must be true for a spontaneous exothermic process?

A)Only $\Delta$ S_sys is less than 0.
B)Only $\Delta$ S_sys is greater than 0.
C)Both $\Delta$ S_sys is less than 0 and the magnitude of $\Delta$ S_sys is less than the magnitude of $\Delta$ S_surr.
D)Both $\Delta$ S_sys is less than 0 and the magnitude of $\Delta$ S_sys is greater than the magnitude of $\Delta$ Ssurr.
E)Either $\Delta$ S_sys is greater than 0 or $\Delta$ S_sys is less than 0 and the magnitude of $\Delta$ S_sys is less than the magnitude of $\Delta$ S_surr.

Question 43

The enthalpy of vaporization of ammonia at its normal boiling point,-33.34 $\degree$ C, is approximately 23.35 kJ/mol.What is the entropy change in the surroundings when one mole of liquid ammonia vaporizes at -33.34 $\degree$ C in a large room maintained at a temperature of 25.0 $\degree$ C?

A)(-2.40 *102 J/K)
B)(-78.3 J/K)
C)(-19.1 J/K)
D)(+78.3 J/K)
E)(+2.40 * 10² J/K)

Question 44

Which of the following statements regarding reversible processes is NOT true?

A)Heat transfer between the system and surroundings usually occurs reversibly during ordinary chemical reactions.
B)The change in entropy of the universe is zero during a reversible process.
C)The entropy change in the surroundings is equal and opposite to that of the system during a reversible process.
D)Reversible change would require an infinite amount of time to complete.
E)Heat transfer between the system and surroundings during phase changes can be approximated as reversible.

Question 45

The entropy change of the surroundings, $\Delta$ S_surr, is related to heat transfer q with respect to the system and temperature T by

A)(-q/Tsys = $\Delta$ Ssurr .)
B)(+q/Tsys = $\Delta$ Ssurr .)
C)(-q/Tsurr = $\Delta$ Ssurr .)
D)(q/Tsurr = $\Delta$ Ssurr .)
E)none of these, unless the system undergoes a reversible process

Question 46

The enthalpy of vaporization of water at 100.0 $\degree$ C is 40.68 kJ/mol.What is the entropy change in the surroundings when one mole of water vapor condenses at 100.0 $\degree$ C in a large room maintained at a temperature of 25.00 $\degree$ C?

A)(-136.4 J/K)
B)(-109.0 J/K)
C)(-40.68 J/K)
D)(+109.0 J/K)
E)(+136.4 J/K)

Question 47

Determine $\Delta$ S $\degree$ for the reaction N₂O₄ (g) ⇄ 2 NO₂ (g) given the following information.

A)(+176.6 J/mol . K)
B)(-63.8 J/mol . K)
C)(+63.8 J/mol . K)
D)(-50.7 J/mol . K)
E)(-176.7 J/mol . K)

Question 48

What is the entropy change in the surroundings when one mole of ice melts at 0.00 $\degree$ C in a large room maintained at 32.0 $\degree$ C? The heat of fusion of ice is 6.01 kJ/mol.

A)(-188 J/K)
B)(-22.0 J/K)
C)(-19.7 J/K)
D)(+19.7 J/K)
E)(+188 J/K)

Question 49

The gas above the liquid in a sealed bottle of soda is primarily carbon dioxide.Carbon dioxide is also dissolved in the soda.When the distribution of carbon dioxide between the gas and liquid is at equilibrium, molecules of carbon dioxide in the gas phase can still dissolve in the liquid phase if they strike the surface and are captured.Similarly, molecules of carbon dioxide can escape from the liquid phase.What is the entropy change of the universe, $\Delta$ S_univ, for the dissolution of carbon dioxide under these conditions?

A)( $\Delta$ S_univ is less than 0 because the dissolved carbon dioxide has fewer accessible states.)
B)( $\Delta$ S_univ is greater than 0 because the dissolved carbon dioxide has fewer accessible states.)
C)( $\Delta$ S_univ equals 0 because this is an equilibrium situation.)
D)( $\Delta$ S_univ is less than 0 because the gas dissolves spontaneously.)
E)( $\Delta$ S_univ is greater than 0 because the gas dissolves spontaneously.)

Question 50

Indicate which of the following reactions results in a positive $\Delta$ S_sys.

A)Ba(NO₃ )₂ (aq) + Na₂ SO₄ (aq) ⇆ BaSO₄ (s) + 2 NaNO₃ (aq)
B)4 Fe(s) +3 O₂ (g) ⇆ 2 Fe₂ O₃ (s)
C)2 H₂ (g) + O₂ (g) ⇆ 2 H₂ O(g)
D)Zn(s) + 2 HCl(aq) ⇆ ZnCL₂ (aq) + H₂ (g)
E)2 Na(s) + CL₂ (g) ⇆ NaCl(s)

Question 51

Determine $\Delta$ S $\degree$ for the reaction 2 Fe₂O₃(s) ⇆ 4 Fe (s) + 3O₂ (g) given the following information.

A)(-144.9 J/mol . K)
B)(-549.4 J/mol . K)
C)(+899.0 J/mol . K)
D)(+549.4 J/mol . K)
E)(+144.9 J/mol . K)

Question 52

When solid pellets of sodium hydroxide (NaOH) dissolve in water, the temperature of the water can rise dramatically.Taking NaOH as the system, what can you deduce about the signs of the entropy change of the system ( $\Delta$ S_sys) and surroundings ( $\Delta$ S_surr) from this?

A)( $\Delta$ S_sys is less than 0 and $\Delta$ S_surr is less than 0.)
B)( $\Delta$ S_sys is less than 0 and $\Delta$ S_surr is greater than 0.)
C)( $\Delta$ S_sys is greater than 0 and $\Delta$ S_surr is less than 0.)
D)( $\Delta$ S_sys is greater than 0 and $\Delta$ S_surr is greater than 0.)
E)Nothing can be deduced from this limited information.

Question 53

When solid ammonium nitrate (NH₄NO₃) dissolves in water, the temperature of the water can drop dramatically.Taking NH₄NO₃ as the system, predict the signs of the entropy change of the system ( $\Delta$ S_sys) and surroundings ( $\Delta$ S_surr).

A)( $\Delta$ S_sys is less than 0 and $\Delta$ S_surr is less than 0.)
B)( $\Delta$ S_sys is less than 0 and $\Delta$ S_surr is greater than 0.)
C)( $\Delta$ S_sys is greater than 0 and $\Delta$ S_surr is less than 0.)
D)( $\Delta$ S_sys is greater than 0 and $\Delta$ S_surr is greater than 0.)
E)( $\Delta$ S_sys equals 0 and $\Delta$ S_surr is less than 0.)

Question 54

The enthalpy and entropy of vaporization of water at 100.00 $\degree$ C are 40.66 kJ/mol and 109.0 J/mol . K, respectively.What is the entropy change of the universe when one mole of steam condenses in a large room maintained at 25.00 $\degree$ C? Assume the final temperature of the water is 100.00 $\degree$ C.

A)(+136.4 J/K)
B)(-136.4 J/K)
C)(+27.4 J/K)
D)(-27.4 J/K)
E)(+245.4 J/K)

Question 55

The enthalpy and entropy of vaporization of acetone at its normal boiling point, -56.4 $\degree$ C, are 31.3 kJ/mol and 95.0 J/mol . K, respectively.What would the entropy change of the universe be if one mole of acetone vapor were to condense in a large room maintained at 25.0 $\degree$ C?

A)(-2.0 * 10² J/K)
B)(+10.0 J/K)
C)(+1.05 * 10² J/K)
D)(-10.0 J/K)
E)(+2.0 * 10² J/K)

Question 56

Which of the following processes are reversible in the thermodynamic sense? I.Iron in the open air rusts.
II.NaCl is dissolved in water and then recovered by the evaporation of the water.
III.The ice in a mixture of ice and water at 0 $\degree$ C and 1 atm melts.

A)I only
B)II only
C)III only
D)II and III only
E)I, II, and III are all reversible.

Question 57

The enthalpy and entropy of vaporization of ammonia at its normal boiling point, -33.34 $\degree$ C, are 23.35 kJ/mol and 97.4 J/mol . K, respectively.What is the entropy change of the universe when one mole of liquid ammonia vaporizes in a large room maintained at 34.0 $\degree$ C? Assume the final temperature of the ammonia gas is -33.34 $\degree$ C.

A)(+21.4 J/K)
B)(-76.0 J/K)
C)(+74.1 J/K)
D)(-21.4 J/K)
E)(+76.0 J/K)

Question 58

$\Delta$ S_sys can be directly related to the heat q.Which of the following statements is NOT true?

A)( $\Delta$ S_sys can always be determined from the heat transferred during the actual process.)
B)For a reversible spontaneous endothermic process, both q and $\Delta$ S_sys will be positive.
C)The greater the amount of heat transferred, the larger the magnitude of the entropy change.
D)The higher the temperature at which heat is transferred, the lower the entropy change.
E)All of these statements are true.

Question 59

Determine $\Delta$ S $\degree$ for the reaction Zn(s) + 2 HCl (aq) ⇄ ZnCL₂ (aq) +H₂ (g) given the following information:

A)0 J/K
B)(-23.1 J/K)
C)(+23.1 J/K)
D)(-33.4 J/K)
E)(+33.4 J/K)

Question 60

Heat transfer from the system to the surroundings has a large effect on $\Delta$ S_surr

A)when the temperature of the surroundings is low.
B)when the temperature of the surroundings is high.
C)when the temperature of the system is low.
D)when the temperature of the system is high.
E)at any temperature, as the amount of heat transferred is independent of temperature.

Question 61

Determine the value of $\Delta$ G $\degree$ at 25 $\degree$ C for the reaction O₃(g) +N₂ O(g) ⇄ O₂(g) + 2 NO(g) given the following information:

A)(-94.2 kJ)
B)(+5.8 kJ)
C)(+50.0 kJ)
D)(-50.0 kJ)
E)(-40.0 kJ)

Question 62

Zinc sulfide can be oxidized by oxygen gas according to the reaction 2 ZnS(s) +O₂ (g) ? 2 ZnO(s) + S(s).If $\Delta$ H $\degree$ =-289.0 kJ/mol and $\Delta$ S $\degree$ =-169.4 J/K.mol, what is $\Delta$ G $\degree$ For this reaction at 25.00 $\degree$ C?

A)(-284.8 kJ/mol)
B)(-238.5 kJ/mol)
C)339.5 kJ/mol
D)50.80 kJ/mol
E)(-339.5 kJ/mol)

Question 63

Methane and water vapor can react to form carbon monoxide and hydrogen gas according to the reaction CH₄ (g) + H₂O(g) ⇄ CO(g) +3 H₂ (g).If $\Delta$ H $\degree$ = 206.1 kJ/mol and $\Delta$ S $\degree$ = 214.5 J/mol .K, what is $\Delta$ G $\degree$ for this reaction at 25.00 $\degree$ C?

A)(-6.375 *10⁴ kJ/mol)
B)(-8.400 kJ/mol)
C)142.1 kJ/mol
D)205.9 kJ/mol
E)(-5156 kJ/mol)

Question 64

At constant T and P, any reaction will be spontaneous if

A)( $\Delta$ Gsys $\gt$ 0.)
B)( $\Delta$ Gsys $\lt$ 0.)
C)( $\Delta$ Ssys $\gt$ 0.)
D)( $\Delta$ Ssys $\lt$ 0.)
E)( $\Delta$ Hsys $\lt$ 0.)

Question 65

Estimate the standard molar entropy of 1.00 M aqueous Mg²⁺ using the following information: $\Delta$ S $\degree$ for the reaction Mg(s) + 2 HCl(aq) ⇄ MgCL₂ (aq) +H₂ (g) is -43.02 J/K.

A)(-52.1 J/K)
B)(+140.J/K)
C)(+138 J/K)
D)(-138 J/K)
E)(-140.J/K)

Question 66

The symbol $\Delta$ G $\degree$ _f NO₂, (g) refers to which of the following reactions?

A)NO₂(l) $\rightarrow$ NO₂(g)
B)NO(g) +O(g) $\rightarrow$ NO₂(g)
C)N(g) + O₂(g) $\rightarrow$ NO₂(g)
D)N(g)+2 O(g) $\rightarrow$ NO₂(g)
E)1/2 N₂(g) +O₂(g) $\rightarrow$ NO₂(g)

Question 67

Processes are always spontaneous when _______ (H and S refer to the system).

A)( $\Delta$ H > 0 and $\Delta$ S < 0
B)( $\Delta$ H $\lt$ 0 and $\Delta$ S < 0
C)( $\Delta$ H > 0 and $\Delta$ S $\gt$ 0
D)( $\Delta$ H $\lt$ 0 and $\Delta$ S $\gt$ 0
E)(None of these is true, as temperature must always be taken into account.

Question 68

For the dimerization of nitrogen dioxide to form dinitrogen tetroxide (N₂O₄) according to the reaction 2 NO₂ (g) ⇄ N₂ O₄ (g), the value of $\Delta$ H $\degree$ is -57.2 kJ/mol, and that of $\Delta$ S $\degree$ is -175.8 J/mol . K.Determine $\Delta$ G $\degree$ at 25.00 $\degree$ C.

A)(+5.236 * 10⁴ kJ/mol)
B)(-52.8 kJ/mol)
C)(-4.8 kJ/mol)
D)(-109.6 kJ/mol)
E)(-61.6 kJ/mol)

Question 69

Determine $\Delta$ G_rxn for C4 H₁₀ (l) +13/2 O₂ (g) $\rightarrow$ 4 CO₂(g) + 5 H₂O(g) given the following information.

A)(-2705.5 kJ/mol)
B)(-608.0 kJ/mol)
C)(-1791.0 kJ/mol)
D)(-2735.5 kJ/mol)
E)(+608.0 kJ/mol)

Question 70

For the dimerization of nitrogen dioxide to form dinitrogen tetroxide (N₂O₄) according to the reaction 2 NO₂ (g) ⇄ N₂ O₄ (g), the value of $\Delta$ H $\degree$ is -57.2 kJ/mol, and that of $\Delta$ S $\degree$ is -175.8 J/mol . K.Estimate
$\Delta$ G $\degree$ at 100.00 $\degree$ C.

A)(+6.6 kJ/mol)
B)(-39.6 kJ/mol)
C)(-122.8 kJ/mol)
D)(-74.8 kJ/mol)
E)(+8.4 kJ/mol)

Question 71

Determine the standard entropy change of the universe at 25 $\degree$ C for the reaction
NH₄ ⁺ (aq) + Cl ^- (aq) $\rightarrow$ NH₄ Cl(s) given the following information.Is the reaction spontaneous under Standard conditions?

A)(-26.0 J/K, no)
B)(+49.3 J/K, yes)
C)(-75.3 J/K, no)
D)(+124.6 J/K, yes)
E)(+26.0 J/K, yes)

Question 72

At body temperature, many proteins have a well-defined structure that is essential to their function.As the temperature is raised, however, the structure changes and the protein no longer functions.What can be deduced from this information about the signs of the enthalpy and entropy changes for denaturation?

A)( $\Delta$ H $\gt$ 0 and $\Delta$ S $\gt$ 0)
B)( $\Delta$ H $\gt$ 0 and $\Delta$ S $\lt$ 0)
C)( $\Delta$ H $\lt$ 0 and $\Delta$ S $\gt$ 0)
D)( $\Delta$ H $\lt$ 0 and $\Delta$ S $\lt$ 0)
E)There is insufficient information to deduce anything about the signs of $\Delta$ H and $\Delta$ S

Question 73

Calculate the maximum amount of work that can be done by the reaction CH₄(g) + 2 O₂(g) ⇄ CO₂(g)+2 H₂O(g) given the following information.

A)(-673.8 kJ/mol)
B)(-750.9 kJ/mol)
C)(-902.3 kJ/mol)
D)(-216.6 kJ/mol)
E)(-800.7 kJ/mol)

Question 74

The dissolution of ammonium nitrate in water is a spontaneous endothermic process.It is spontaneous because the system undergoes

A)a decrease in enthalpy.
B)an increase in entropy.
C)an increase in enthalpy.
D)a decrease in entropy.
E)an increase in free energy.

Question 75

Which of the following statements regarding free energy, work, and efficiency is NOT correct?

A)The thermal energy released during combustion reactions can be completely converted into useful work.
B)The enthalpy change associated with a chemical reaction can theoretically be divided into the energy available to do useful work and the energy that spreads out.
C)In the free energy equation, the T $\Delta$ S term equals the P-V work done by the system.
D)For a nonspontaneous reaction to occur, work must be done on the reaction system.
E)Maximum efficiency requires that a reaction occur infinitely slowly and reversibly.

Question 76

Which of the relationships between the free energy change of a system and associated entropy changes is true?

A)( $\Delta$ Gsys = +T $\Delta$ Ssys)
B)( $\Delta$ Gsys =-T $\Delta$ Ssys)
C)( $\Delta$ Gsys =+T $\Delta$ Suniv)
D)( $\Delta$ Gsys = -T $\Delta$ Ssurr)
E)( $\Delta$ Gsys = -T $\Delta$ Suniv)

Question 77

Consider substances that exist as liquids under standard state conditions.What must be the relationship between the enthalpy and free energy of formation for the liquid and the gaseous form of the substance? (Read $\lt$ as more negative and $\lt$ as less negative.)

A)H_f⁰(l) $\lt$ H_f⁰(g) and G_f⁰(l) $\lt$ G_f⁰ (g)
B)H_f⁰(l) $\lt$ H_f⁰(g) and G_f⁰(l) $\gt$ G_f⁰ (g)
C)H_f⁰(l) $\gt$ H_f⁰(g) and G_f⁰(l) $\gt$ G_f⁰ (g)
D)H_f⁰(l) $\gt$ H_f⁰(g) and G_f⁰(l) $\lt$ G_f⁰ (g)
E)No strict relationship between these values applies.

Question 78

Indicate which of the following reactions results in a negative $\Delta$ S_sys.

A)AgNO₃ (aq) + NaCl(aq) ⇄ AgCl(s) + NaCl(aq)
B)2 C₂ H₆ (g) +7 O₂ (g) ⇄ 4 CO₂ (g) +6 H₂ O(g)
C)MgSO₄ . 7 H₂ O(s) ⇄ MgSO₄ (s) +7 H₂ O(g)
D)N₂ O₄ (g) ⇄ 2 NO₂ (g)
E)Fe(OH)₃ (s) + 3H⁺(aq) ⇄ 3H₂O(l) + Fe³⁺(aq)

Question 79

Hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to form sodium chloride (NaCl) and water.If $\Delta$ H $\degree$ =-56.13 kJ/mol and $\Delta$ S $\degree$ =79.11 J/mol. K, what is $\Delta$ G $\degree$ for this reaction at 20.00 $\degree$ C?

A)(-79.32 kJ/mol)
B)(-77.73 kJ/mol)
C)(-2.324 *10⁴ kJ/mol)
D)79.32 kJ/mol
E)(-1638 kJ/mol)

Question 80

Which of the following statements regarding free energy is NOT true?

A)Free energy represents the maximum work that a thermodynamic system can perform during a spontaneous change.
B)Free energy represents the minimum work that would be required to make a thermodynamic system undergo a nonspontaneous change.
C)The free energy of a system increases during the course of a spontaneous reaction as the entropy of the universe increases.
D)The Gibbs free energy change of a reaction reflects the work associated with processes happening at constant temperature and pressure.
E)The Gibbs free energy change of a spontaneous process is negative.