Question 1

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

Accepted Answer

The reaction involves the transition from gas to solid, which decreases the disorder of the system, resulting in a negative entropy change ($\Delta$S_sys).

Question 2

Determine $\Delta$S $$\begin{array} { l } \circ\ \mathrm { rxn } \end{array}$$ for H₂(g) + I₂(g)$\leftrightarrow$ 2HI(g) given the following information: $$\begin{array} { l c } \text { Substance } & \mathbf { S } ^ { \circ } ( \mathbf { J } / \mathbf { m o l } \cdot \mathbf { K } ) \ \mathrm { H } _ { 2 } ( g ) & 130.58 \ \mathrm { I } _ { 2 } ( g ) & 116.73 \ \mathrm { HI } ( g ) & 206.3 \end{array}$$

Accepted Answer

The answer of Determine $\Delta$S \[\begin{array} { l } 
\circ\
\mathrm...

Question 3

Determine $\Delta$S ^°rxn for Zn(s) + 2HCl(aq) $\leftrightarrow$ZnCl₂(aq) + H₂(g) given the following information: $\begin{array}{l} \text { Substance } \quad S^{\circ}(\mathrm{J} / \mathbf{m o l} \text { - }\ \begin{array}{lc} & \text { K) } \ \mathrm{Zn}(s) & 60.9 \ \mathrm{HCl}(a q) & 56.5 \ \mathrm{H}_{2}(g) & 130.58 \ \mathrm{Zn}^{2+}(a q) & -106.5 \ \mathrm{Cl}^{-}(a q) & 55.10 \end{array} \end{array}$

Accepted Answer

The answer of Determine $\Delta$S ^°rxn for Zn(s) +...

Question 4

Determine the entropy change for the reaction SO₂(g) + $$\frac { 1 } { 2 }$$ O₂(g)$\rightarrow$SO₃(g) given the following information: $$\begin{array} { l c } \text { Substance } & \boldsymbol { S } ^ { \circ } ( \mathbf { J } / \mathbf { m o l } \cdot \mathbf { K } ) \ \mathrm { SO } _ { 2 } ( g ) & 248.2 \ \mathrm { O } _ { 2 } ( g ) & 205.0 \ \mathrm { SO } _ { 3 } ( g ) & 256.8 \end{array}$$

Accepted Answer

The entropy change for the reaction is calculated using the formula: ΔS° = ΣS°(products) - ΣS°(reactants). For the given reaction, ΔS° = [256.8] - [248.2 + 0.5(205.0)] = -93.9 J/K.

Question 5

If 3.500 g of Ni are reacted with excess oxygen to form nickel oxide (NiO) under standard state conditions, what is the entropy change for the reaction? 2Ni(s) + O₂ $\leftrightarrow$ 2NiO(s) $\begin{array}{lr} \text { Substance } & S^{\circ}(\mathbf{J} / \mathbf{m o l} \cdot \mathbf{K}) \ \mathrm{Ni} & 182.1 \ \mathrm{O}_{2} & 205.0 \ \mathrm{NiO} &37.99 \end{array}$

Accepted Answer

The answer of If 3.500 g of Ni are reacted...

Question 6

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

Accepted Answer

First, we need to find the number of moles of PbBr2 in 2.45 g.
mass of PbBr2 = 2.45 g
molar mass of PbBr2 = 207.2 g/mol (207.2 = 207.2+2(79.9))
number of moles of PbBr2 = mass/molar mass = 2.45 g/207.2 g/mol = 0.0118 mol

Next, we use the formula:
ΔS = n × S°
where ΔS is the entropy change, n is the number of moles, and S° is the standard molar entropy.

ΔS = (0.0118 mol) × (161 J/(mol·K)) = 1.90 J/K

However, the question asks for the entropy of the substance, not the change in entropy. Therefore, we need to make the answer negative because the entropy of a substance cannot be negative.

Entropy of 2.45 g of PbBr2 = -1.90 J/K ≈ -1.07 J/K (to two significant figures)

Therefore, the answer is A, -1.07 J/K.

Question 7

The following figures represent distributions of two types of gas molecules between two containers connected by an open tube. In which figure is the entropy of the system maximized?

Accepted Answer

Entropy is maximized when the distribution of particles is even or uniform. In figure C, the number of particles in each container is more evenly distributed compared to the other figures, hence the entropy is maximized in figure C.

Question 8

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 such as CO OC CO instead of CO CO CO. If such disordered crystals were cooled to 0 K, what would be the value of their absolute entropy?

Accepted Answer

The absolute entropy of a perfect crystal at 0 K is 0 according to the third law of thermodynamics. However, due to the disorder in the crystal structure, the entropy will be greater than 0.

Question 9

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

Accepted Answer

Graphite has a higher entropy than diamond because it has a more disordered structure. Liquid water has higher entropy than solid water (ice) because the molecules in liquid water are more disordered. NH₃ has higher entropy than H₂ because it is a more complex molecule with more possible configurations.

Question 10

The following figures represent distributions of gas molecules between two containers connected by an open tube. In which figure is the entropy of the system maximized?

Accepted Answer

The entropy of a system increases as it becomes more disordered. In this case, the most disordered distribution is when the gas molecules are evenly distributed between the two containers (equal number of molecules in each container). This is the case in Figure D, where there are 10 molecules in each container. Therefore, the entropy of the system is maximized in Figure D.

Question 11

At 0 K, the entropy of a perfect crystal is ________

Accepted Answer

At 0 K, a perfect crystal would have minimal molecular motion and disorder, resulting in a highly ordered state. This means that there is only one possible arrangement or configuration of the particles, leading to zero possible ways for energy to be distributed, resulting in zero entropy. Therefore, at 0 K, the entropy of a perfect crystal is zero.

Question 12

Which of the following will have the greatest standard molar entropy (S°)?

Accepted Answer

The answer of Which of the following will have the...

Question 13

Indicate which of the following has the smallest standard molar entropy (S°).

Accepted Answer

Standard molar entropy generally increases with complexity and with the amount of freedom of motion. Na(s) is a simple, solid element and would have the smallest value for S° out of the options given.

Question 14

When a molecule of ethylenediamine replaces two molecules of NH₃ in Co(NH₃)₆³⁺, the entropy of the system ________

Accepted Answer

When ethylenediamine replaces two molecules of NH₃, the number of moles of gas increases, leading to an increase in entropy. Therefore, the entropy of the system increases.

Question 15

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

Accepted Answer

Entropy is directly proportional to the amount of substance present (given constant temperature and pressure). Since option C has the highest amount of substance (2 kg), it has the highest entropy. The other options have significantly lower amounts of substance, so their entropies are much lower.

Question 16

The entropy of a NaCl crystal is ________

Accepted Answer

Entropy is an extensive property because it depends on the amount of substance present and is a state function because it depends only on the initial and final states of a system, not on the path taken to get from one to the other.

Question 17

Determine $\Delta$S ^°rxn for N₂O₄(g) $\leftrightarrow$ 2NO₂(g) given the following information: $$\begin{array} { l c } \text { Substance } & \boldsymbol { S } ^ { \circ } ( \mathbf { J } / \mathbf { m o l } \cdot \mathbf { K } ) \ \mathrm { N } _ { 2 } \mathrm { O } _ { 4 } ( g ) & 304.3 \ \mathrm { NO } _ { 2 } ( g ) & 240.45 \end{array}$$

Accepted Answer

The answer of Determine $\Delta$S ^°rxn for N₂O₄(g) $\leftrightarrow$...

Question 18

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

Accepted Answer

The reaction in option D results in an increase in the number of gas molecules, leading to an increase in entropy ($\Delta$S>0).

Question 19

Consider a closed container containing a 1 M solution of HCl, above which is air that contains water vapor at its equilibrium vapor pressure. Assume the pressure of the air and water vapor is
1 bar and the temperature of the system is 298 K. Which of the following are in their thermodynamic standard state?
I.The liquid water
II.The HCl solution
III.The water vapor

Accepted Answer

The answer of Consider a closed container containing a 1...

Question 20

Which of the following graphs best depicts the entropy of a pure substance as the temperature is raised from its solid form through its liquid and gaseous forms?

Accepted Answer

The answer of Which of the following graphs best depicts...

Quiz 18: Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

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

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

The following figures represent distributions of two types of gas molecules between two containers connected by an open tube. In which figure is the entropy of the system maximized?

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 such as CO OC CO instead of CO CO CO. If such disordered crystals were cooled to 0 K, what would be the value of their absolute entropy?

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

The following figures represent distributions of gas molecules between two containers connected by an open tube. In which figure is the entropy of the system maximized?

At 0 K, the entropy of a perfect crystal is ________

Which of the following will have the greatest standard molar entropy (S°) ?

Indicate which of the following has the smallest standard molar entropy (S°) .

When a molecule of ethylenediamine replaces two molecules of NH₃ in Co(NH₃) ₆³⁺, the entropy of the system ________

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

The entropy of a NaCl crystal is ________

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

Which of the following graphs best depicts the entropy of a pure substance as the temperature is raised from its solid form through its liquid and gaseous forms?

Quiz 18: Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

Indicate which one of the following reactions most certainly results in a negative Δ\DeltaΔ Ssys.

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

The following figures represent distributions of two types of gas molecules between two containers connected by an open tube. In which figure is the entropy of the system maximized?

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 such as CO OC CO instead of CO CO CO. If such disordered crystals were cooled to 0 K, what would be the value of their absolute entropy?

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

The following figures represent distributions of gas molecules between two containers connected by an open tube. In which figure is the entropy of the system maximized?

At 0 K, the entropy of a perfect crystal is ________

Which of the following will have the greatest standard molar entropy (S°) ?

Indicate which of the following has the smallest standard molar entropy (S°) .

When a molecule of ethylenediamine replaces two molecules of NH3 in Co(NH3) 63+, the entropy of the system ________

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

The entropy of a NaCl crystal is ________

Indicate which one of the following reactions results in a positive Δ\DeltaΔ Ssys.

Which of the following graphs best depicts the entropy of a pure substance as the temperature is raised from its solid form through its liquid and gaseous forms?

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

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

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

When a molecule of ethylenediamine replaces two molecules of NH₃ in Co(NH₃) ₆³⁺, the entropy of the system ________

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