Question 1

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

Accepted Answer

For a spontaneous process, the total entropy change ($\Delta$S_univ = $\Delta$S_sys + $\Delta$S_surr) must be positive. If $\Delta$S_sys < 0, then $\Delta$S_surr must be positive and greater in magnitude than $\Delta$S_sys to ensure $\Delta$S_univ > 0.

Question 2

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

Accepted Answer

Heat transfer from the system to the surroundings has a larger effect when the temperature of the surroundings is low because the temperature gradient between the system and its surroundings is greater, leading to more significant changes in entropy and other thermodynamic properties.

Question 3

What is the entropy change to the surroundings when 1 mol of ice melts in someone's hand if the hand temperature is 32°C? Assume a final temperature for the water of 0°C. The heat of fusion of ice is 6.01 kJ/mol.

Accepted Answer

The entropy change to the surroundings can be calculated using the formula:

ΔS = -q/T

where q is the heat absorbed or released, and T is the temperature at which the transfer of heat occurs.

In this case, the heat absorbed is the heat of fusion of 1 mol of ice, which is 6.01 kJ. Since the ice melts in someone's hand, we can assume that the hand is at the same temperature as the ice initially, which is 0°C (273 K). The final temperature of the water is also given as 0°C.

Therefore, the change in temperature is:

ΔT = Tfinal - Tinitial
ΔT = 0°C - 273 K = -273 K

Substituting the values into the formula, we get:

ΔS = -(6.01 kJ/mol)/(273 K)
ΔS = -22.006 J/K
ΔS ≈ -19.7 J/K (to 3 significant figures)

Therefore, the entropy change to the surroundings is approximately -19.7 J/K, which corresponds to answer choice C.

Question 4

Which of the following processes are spontaneous?
I.Iron in the open air rusts.
II.Liquid water in a freezer turns to ice.
III.A spark ignites a mixture of propane and air.

Accepted Answer

All three processes are spontaneous as they occur naturally under the given conditions without external intervention. Rusting of iron, freezing of water in a freezer, and ignition of propane with a spark are all spontaneous processes.

Question 5

Care must be taken when dissolving solid pellets of sodium hydroxide (NaOH) in water, because 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?

Accepted Answer

Dissolving NaOH in water is an exothermic process, increasing the entropy of the surroundings ($\Delta$S_surr > 0) due to heat release. The dissolution also increases the disorder of the system ($\Delta$S_sys > 0) as the solid becomes a solute in solution.

Question 6

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

Accepted Answer

For a spontaneous exothermic process, the total entropy change ($\Delta$S_universe) must be positive. This can occur if $\Delta$S_sys is positive or if $\Delta$S_sys is negative but the increase in $\Delta$S_surr is greater, making the overall $\Delta$S_universe positive.

Question 7

If 1 mol of ice melts at its melting point of 273 K, the entropy change for the ice is 22.0 J/K. If the ice melts in someone's hand at 34°C, what is the change in the entropy of the universe? Assume a final temperature for the water of 0°C. The enthalpy of fusion for ice is 6.01 kJ/mol.

Accepted Answer

The entropy change of the universe is the sum of the entropy change of the system (ice) and the surroundings (hand). The entropy change of the ice is 22.0 J/K. The entropy change of the surroundings is calculated as -ΔH/T, where ΔH is the enthalpy of fusion (6010 J) and T is the temperature of the surroundings in Kelvin (307 K). This gives -6010/307 = -19.6 J/K. The total change in entropy of the universe is 22.0 - 19.6 = +2.4 J/K.

Question 8

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

Accepted Answer

According to the Second Law of Thermodynamics, the entropy of the universe always increases in a spontaneous process. This is because the entropy of the system and surroundings may decrease, but the overall entropy of the universe must increase to satisfy the law. Choice A and B might increase or decrease depending on the process, while choice D and E are too broad and therefore incorrect.

Question 9

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

Accepted Answer

The answer of The entropy change in a system ($\Delta$S_sys)...

Question 10

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?

Accepted Answer

At equilibrium, the entropy change of the universe ($\Delta$S_univ) is zero because the forward and reverse processes occur at the same rate, resulting in no net change in entropy.

Question 11

The enthalpy of fusion for benzene (C₆H₆) is 127.40 kJ/kg, and its melting point is 5.5°C. What is the entropy change when 1 mole of benzene melts at 5.5°C?

Accepted Answer

The entropy change (ΔS) can be calculated using the formula ΔS = ΔH/T, where ΔH is the enthalpy change and T is the temperature in Kelvin. First, convert the enthalpy of fusion from kJ/kg to J/mol using the molar mass of benzene (78.11 g/mol), then convert the temperature to Kelvin (5.5°C = 278.65 K). Calculate ΔS = (127.40 kJ/kg * 78.11 g/mol * 1000 J/kJ) / 278.65 K = 35.7 J/K.

Question 12

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°C and 1 atm melts.

Accepted Answer

The answer of Which of the following processes are reversible...

Question 13

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

Accepted Answer

The answer of The entropy change of the surroundings, $\Delta$S_surr,...

Question 14

Which of the processes A-D will lead to a positive change in the entropy of the system? If all of these processes lead to a positive change in the entropy of the system, select E.

Accepted Answer

When helium gas escapes from a balloon, the gas molecules spread out into a larger volume, increasing the disorder and thus the entropy of the system.

Question 15

Which of the following processes will lead to a decrease in the entropy of the system?

Accepted Answer

The formation of rust involves the arrangement of iron and oxygen atoms into a more ordered structure, therefore decreasing entropy. The other options all involve an increase in entropy.

Question 16

$\Delta$S_sys can be directly related to the heat, q. Which of statements A-D is not true regarding this relationship? If all are true, select E.

Accepted Answer

$\Delta$S_sys can only be determined from the heat transferred if the process is reversible. In irreversible processes, additional factors must be considered.

Question 17

In a spontaneous process, the entropy of the universe ________

Accepted Answer

The second law of thermodynamics states that the entropy of the universe (system + surroundings) always increases in a spontaneous process. Therefore, choice A is the correct answer.

Question 18

An ice cube at 0°C melts in a swimming pool at 20°C. What is the change in the entropy of the universe as a result? The ice cube was 1.00 inch on a side. Assume ice has a density of 0.917 g/cm³ and that the enthalpy of fusion of water is 6.01 kJ/mol.

Accepted Answer

The change in entropy of the universe is positive because the ice cube melts, which increases the disorder of the system. The entropy of the universe is also increased by the heat that is transferred from the swimming pool to the ice cube.

Question 19

Which, if any, of statements A through D is not true of entropy? If they are all true, select E.

Accepted Answer

All of the statements A through D are true of entropy.

Question 20

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

Accepted Answer

The second law of thermodynamics states that the entropy of the universe always increases during a spontaneous process. Therefore, the change in entropy of the universe (F1F1F1S1F1F1F10S_univ) is always positive.

Quiz 18: Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

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

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

What is the entropy change to the surroundings when 1 mol of ice melts in someone's hand if the hand temperature is 32°C? Assume a final temperature for the water of 0°C. The heat of fusion of ice is 6.01 kJ/mol.

Which of the following processes are spontaneous? I.Iron in the open air rusts. II.Liquid water in a freezer turns to ice. III.A spark ignites a mixture of propane and air.

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

If 1 mol of ice melts at its melting point of 273 K, the entropy change for the ice is 22.0 J/K. If the ice melts in someone's hand at 34°C, what is the change in the entropy of the universe? Assume a final temperature for the water of 0°C. The enthalpy of fusion for ice is 6.01 kJ/mol.

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

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

The enthalpy of fusion for benzene (C₆H₆) is 127.40 kJ/kg, and its melting point is 5.5°C. What is the entropy change when 1 mole of benzene melts at 5.5°C?

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°C and 1 atm melts.

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

Which of the processes A-D will lead to a positive change in the entropy of the system? If all of these processes lead to a positive change in the entropy of the system, select E.

Which of the following processes will lead to a decrease in the entropy of the system?

$\Delta$ S_sys can be directly related to the heat, q. Which of statements A-D is not true regarding this relationship? If all are true, select E.

In a spontaneous process, the entropy of the universe ________

An ice cube at 0°C melts in a swimming pool at 20°C. What is the change in the entropy of the universe as a result? The ice cube was 1.00 inch on a side. Assume ice has a density of 0.917 g/cm³ and that the enthalpy of fusion of water is 6.01 kJ/mol.

Which, if any, of statements A through D is not true of entropy? If they are all true, select E.

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

Quiz 18: Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

During a spontaneous chemical reaction, it is found that Δ\DeltaΔ Ssys < 0. This means ________

Heat transfer from the system to the surroundings has a large effect on Δ\DeltaΔ Ssurr ________

What is the entropy change to the surroundings when 1 mol of ice melts in someone's hand if the hand temperature is 32°C? Assume a final temperature for the water of 0°C. The heat of fusion of ice is 6.01 kJ/mol.

Which of the following processes are spontaneous? I.Iron in the open air rusts. II.Liquid water in a freezer turns to ice. III.A spark ignites a mixture of propane and air.

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

If 1 mol of ice melts at its melting point of 273 K, the entropy change for the ice is 22.0 J/K. If the ice melts in someone's hand at 34°C, what is the change in the entropy of the universe? Assume a final temperature for the water of 0°C. The enthalpy of fusion for ice is 6.01 kJ/mol.

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

The entropy change in a system ( Δ\DeltaΔ Ssys) during a spontaneous process must be ________

The enthalpy of fusion for benzene (C6H6) is 127.40 kJ/kg, and its melting point is 5.5°C. What is the entropy change when 1 mole of benzene melts at 5.5°C?

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°C and 1 atm melts.

The entropy change of the surroundings, Δ\DeltaΔ Ssurr, is related to heat transfer, q, with respect to the system and temperature T by ________

Which of the processes A-D will lead to a positive change in the entropy of the system? If all of these processes lead to a positive change in the entropy of the system, select E.

Which of the following processes will lead to a decrease in the entropy of the system?

Δ\DeltaΔ Ssys can be directly related to the heat, q. Which of statements A-D is not true regarding this relationship? If all are true, select E.

In a spontaneous process, the entropy of the universe ________

An ice cube at 0°C melts in a swimming pool at 20°C. What is the change in the entropy of the universe as a result? The ice cube was 1.00 inch on a side. Assume ice has a density of 0.917 g/cm3 and that the enthalpy of fusion of water is 6.01 kJ/mol.

Which, if any, of statements A through D is not true of entropy? If they are all true, select E.

According to the second law of thermodynamics, the change in the entropy of the universe ( Δ\DeltaΔ Suniv) during a spontaneous reaction is ________

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

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

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

The enthalpy of fusion for benzene (C₆H₆) is 127.40 kJ/kg, and its melting point is 5.5°C. What is the entropy change when 1 mole of benzene melts at 5.5°C?

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

$\Delta$ S_sys can be directly related to the heat, q. Which of statements A-D is not true regarding this relationship? If all are true, select E.

An ice cube at 0°C melts in a swimming pool at 20°C. What is the change in the entropy of the universe as a result? The ice cube was 1.00 inch on a side. Assume ice has a density of 0.917 g/cm³ and that the enthalpy of fusion of water is 6.01 kJ/mol.

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