Question 1

One of the following statements A-D may be incorrect. If so, identify it.

Accepted Answer

All the statements A-D correctly describe the conditions for spontaneity based on the Gibbs free energy equation $\Delta$G = $\Delta$H - T$\Delta$S.

Question 2

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

Accepted Answer

The dissolution of ammonium nitrate in water results in an increase in entropy because the solid ammonium nitrate breaks down into separate ions in solution, increasing the overall disorder of the system. While this process is endothermic (requires energy input), it still has a positive Gibbs free energy change, indicating that it is a spontaneous process.

Question 3

Calcium sulfate is a desiccant used for storage of samples and equipment in a dry atmosphere because it absorbs water from air. The relevant thermodynamic reaction equation is given below. At what temperature will this reaction reverse to release the water and regenerate the dry desiccant?
CaSOS1U1B14S1U1B0(s) + 2HS1U1B12S1U1B0O(g) $\rightarrow$CaSOS1U1B14S1U1B0.HS1U1B12S1U1B0O(s)
$\Delta$H° = -104.9 kJ/mol, $\Delta$S° = -291.2 J/(mol K)

Accepted Answer

The answer of Calcium sulfate is a desiccant used for...

Question 4

Which statement characterizes the following table? Temperature Dependence of Reaction Spontaneity $$\begin{array} { | l | l | l | } \hline & { \Delta S < 0 } & { \Delta S > 0 } \ \hline \Delta H < 0 & \begin{array} { l } \text { Spontaneous only at a sufficiently } \ \text { high temperature. } \end{array} & \begin{array} { l } \text { Always spontaneous at any } \ \text { temperature. } \end{array} \ \hline \Delta H > 0 & \begin{array} { l } \text { Never spontaneous at any } \ \text { temperature. } \end{array} & \begin{array} { l } \text { Spontaneous only at a sufficiently } \ \text { low temperature. } \end{array} \ \hline \end{array}$$

Accepted Answer

The answer of Which statement characterizes the following table?
Temperature Dependence...

Question 5

Which of the following must be true for a reaction to proceed to form products?

Accepted Answer

The answer of Which of the following must be true...

Question 6

The entropy of vaporization of water is 109.0 J/mol · K. What is the enthalpy of vaporization of water at its normal boiling point?

Accepted Answer

The enthalpy of vaporization (ΔHvap) can be calculated using the Clausius-Clapeyron equation:

ln(P2/P1) = (ΔHvap/R)(1/T1 - 1/T2)

At the normal boiling point of water, the temperature (T1) is 373 K and the vapor pressure (P1) is 1 atm. At any temperature below the boiling point, the vapor pressure (P2) can be assumed to be negligible or zero. So, we can simplify the equation as:

ln(0) = (ΔHvap/R)(1/373 - 0)

The natural logarithm of zero is undefined, indicating that the equation cannot be solved for ΔHvap. However, we can use the given entropy of vaporization (ΔSvap) to estimate ΔHvap. The relationship between ΔHvap and ΔSvap is:

ΔHvap = TΔSvap

Substituting the values:

ΔHvap = (373 K)(109.0 J/mol · K) = 40.66 kJ/mol

Therefore, the answer is D, +40.66 kJ/mol.

Question 7

A reaction with a low enthalpy of reaction value is not spontaneous at low temperature but becomes spontaneous at high temperature. What are the signs for $\Delta$H° and $\Delta$S°, respectively?

Accepted Answer

For a reaction to be non-spontaneous at low temperatures and spontaneous at high temperatures, $\Delta$H° must be positive and $\Delta$S° must be positive. This is because the T$\Delta$S° term becomes more significant at higher temperatures, allowing the reaction to become spontaneous ($\Delta$G° = $\Delta$H° - T$\Delta$S° < 0).

Question 8

At body temperature, many proteins have a well-defined structure that is essential to their
Function. However, as the temperature is raised, the structure changes and the protein is no longer functional. This process is referred to as protein denaturation. What can be deduced from this information about the signs of the enthalpy and entropy changes for denaturation?

Accepted Answer

Protein denaturation is an endothermic process ($\Delta$H > 0) because it requires heat to break the bonds maintaining the protein's structure. The process also leads to an increase in disorder as the structured protein unfolds, resulting in an increase in entropy ($\Delta$S > 0).

Question 9

Some pure metals can be obtained from their ores simply by heating to a high temperature to drive off the oxygen, but iron ore usually is refined by reacting it with carbon monoxide. Use the information in the following table to determine whether or not iron ore could be refined by heating to a high temperature and, if so, how high the temperature must be. The oxidation reaction producing iron ore is given below. 4Fe(s) + 3O₂(g) $\rightarrow$2Fe₂O₃(s) Thermodynamic Properties $$\begin{array} { | c | c | c | c | } \hline \text { Parameter } & \mathbf { F e } & \mathbf { O } _ { 2 } & \mathrm { Fe } _ { 2 } \mathbf { O } _ { 3 } \ \hline & 0 & 0 & - 742 \ \Delta G _ { \mathrm { f } } ^ { \circ } & & & \ ( \mathrm { kJ } / \mathrm { mol } ) & & & \ \hline &0 & 0& - 824 \ \Delta H _ { \mathrm { f } } ^ { \circ } & & & \ ( \mathrm { kJ } / \mathrm { mol } ) & & & \ \hline & & & \ S ^ { \circ } &27 &205 &87 \ \mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } ) ] & & & \ \hline \end{array}$$

Accepted Answer

The answer of Some pure metals can be obtained from...

Question 10

Alcohols for use as biofuels can be produced from glucose that is obtained from starch and cellulose in plants. Use the information in the table below to determine the temperature range, if any, at which this reaction is spontaneous. C₆H₁₂O₆(s) $\longrightarrow$2CH₃CH₂OH(l) + 2CO₂(g) $$\begin{array} { | c | c | c | } \hline \text { Compound } & & \boldsymbol { S } ^ { \circ } \ & \Delta H _ { \mathrm { f } } ^ { \circ } & { [ \mathbf { J } / ( \mathbf { m o l } \cdot \mathbf { K } ) ] } \ \hline \text { Glucose } ( s ) & ( \mathrm { kJ } / \mathbf { m o l } ) & 212 \ \hline \text { Ethanol } ( l ) & - 1,274 & 161 \ \hline \text { Carbon dioxide } ( g ) & - 278 & 214 \ \hline \end{array}$$

Accepted Answer

The reaction is spontaneous at all temperatures because the change in free energy is negative at all temperatures. This can be seen from the fact that the standard free energy change for the reaction is negative, and the temperature dependence of the free energy change is given by the equation:$$\Delta G = \Delta H - T\Delta S$$where $\Delta H$ is the standard enthalpy change, $\Delta S$ is the standard entropy change, and $T$ is the temperature. Since $\Delta H$ is negative and $\Delta S$ is positive, $\Delta G$ will be negative at all temperatures.

Question 11

When a solution of DNA in water is heated, the double helix separates into two single strands. This process is called melting. What can be deduced from this information about the signs of the enthalpy and entropy changes for DNA melting?

Accepted Answer

The process of DNA melting requires energy to break the hydrogen bonds between the strands, indicating that $\Delta$H > 0. The separation of strands increases disorder, indicating that $\Delta$S > 0.

Question 12

Determine $\Delta$G_rxn for C₄H₁₀(l) + $\frac { 13 } { 2 }$ O₂(g) $\leftrightarrow$ 4CO₂(g) + 5H₂O(g) given the following information: $$\begin{array}{l} \text { Substance }\ \begin{array} { c c c } && \Delta G _ { \mathbf { f } } ^ { \circ } \ & & ( \mathbf { k J } / \mathbf { m o l } ) \ && - 15.0 \ \mathrm { C } _ { 4 } \mathrm { H } _ { 10 } ( l ) & \ & \mathrm { CO } _ { 2 } ( g ) & - 394.4 \ & \mathrm { H } _ { 2 } \mathrm { O } ( g ) & - 228.57 \end{array} \end{array}$$

Accepted Answer

The correct answer is A because $\Delta$G_rxn = 4$\Delta$G_f^o(CO₂) + 5$\Delta$G_f^o(H₂O) - $\Delta$G_f^o(C₄H₁₀) - $\frac { 13 } { 2 }$$\Delta$G_f^o(O₂) = 4(-394.4 kJ/mol) + 5(-228.57 kJ/mol) - (-15.0 kJ/mol) - $\frac { 13 } { 2 }$(0 kJ/mol) = -2705 kJ

Question 13

Which statement characterizes the following table? Temperature Dependence of Reaction Spontaneity $$\begin{array} { | c | l | l | } \hline & { \Delta S < 0 } & { \Delta S > 0 } \ \hline \Delta H < 0 & \begin{array} { l } \text { Spontaneous only at a sufficiently } \ \text { low temperature. } \end{array} & \begin{array} { l } \text { Always spontaneous at any } \ \text { temperature. } \end{array} \ \hline \Delta H > 0 & \begin{array} { l } \text { Never spontaneous at any } \ \text { temperature. } \end{array} & \begin{array} { l } \text { Spontaneous only at a sufficiently } \ \text { high temperature. } \end{array} \ \hline \end{array}$$

Accepted Answer

The table correctly describes the conditions for reaction spontaneity based on the signs of enthalpy change ($\Delta H$) and entropy change ($\Delta S$).

Question 14

What is the maximum amount of work that can be done by the reaction CH₄(g) + 2O₂(g) $\leftrightarrow$CO₂(g) + 2H₂O(g) Given $$\begin{array}{l} \text { Substance }\ \begin{array} { c c } & \Delta G _ { \mathrm { f } } ^ { \circ } \ & ( \mathbf { k J } / \mathbf { m o l } ) \ \mathrm { CH } _ { 4 } ( g ) & 50.8 \ \mathrm { CO } _ { 2 } ( g ) & 394.4 \ \mathrm { H } _ { 2 } \mathrm { O } ( g ) & - 228.57 \end{array} \end{array}$$

Accepted Answer

The answer of What is the maximum amount of work...

Question 15

At what temperature does the Fe(s) $\leftrightarrow$Fe(g) phase transition occur? $\Delta$H= 415.5 kJ/mol; $\Delta$S = 153.4 J/mol · K.

Accepted Answer

The correct answer is D.The phase transition temperature can be calculated using the equation:$$\Delta G = \Delta H - T\Delta S$$At the phase transition temperature, $\Delta G = 0$. Therefore, we can solve for T:$$T = \frac{\Delta H}{\Delta S} = \frac{415.5 kJ/mol}{153.4 J/mol · K} = 2709 K$$Converting to Fahrenheit:$$T = 2709 K \times \frac{9}{5} - 459.67 = 4416°F$$

Question 16

Which statement characterizes the following table? Temperature Dependence of Reaction Spontaneity $$\begin{array} { | c | l | l | } \hline & { \Delta S < 0 } & { \Delta S > 0 } \ \hline \Delta H < 0 & \begin{array} { l } \text { Spontaneous only at a sufficiently } \ \text { high temperature. } \end{array} & \begin{array} { l } \text { Never spontaneous at any } \ \text { temperature. } \end{array} \ \hline \Delta H > 0 & \begin{array} { l } \text { Always spontaneous at any } \ \text { temperature. } \end{array} & \begin{array} { l } \text { Spontaneous only at a sufficiently } \ \text { low temperature. } \end{array} \ \hline \end{array}$$

Accepted Answer

The answer of Which statement characterizes the following table?
Temperature Dependence...

Question 17

Alcohols for use as biofuels can be produced from glucose that is obtained from starch and cellulose in plants. For example, 1 mol of glucose can produce 2 mol of ethanol. Use the information in the table below to determine the maximum amount of work and energy that can be produced by the combustion of glucose compared with that by the combustion of 2 mol of ethanol. C₆H₁₂O₆(s) $\longrightarrow$ 2CH₃CH₂OH(l) + 2CO₂(g) $$\begin{array} { | c | c | } \hline \text { Compound } & \ & \Delta G _ { \mathrm { f } } ^ { \circ } \ & ( \mathbf { k J } / \mathbf { m o l } ) \ \hline \text { Glucose } ( s ) & - 910 \ \hline \text { Ethanol } ( l ) & - 175 \ \hline \text { Water } ( g ) & - 229 \ \hline \text { Carbon dioxide } ( g ) & - 394 \ \hline \end{array}$$

Accepted Answer

The maximum amount of work and energy that can be produced by the combustion of glucose is 2,830 kJ, and that by the combustion of 2 mol of ethanol is 2,600 kJ.

Question 18

Dinitrogen tetroxide (N₂O₄) decomposes to nitrogen dioxide (NO₂). If$\Delta$H° = 58.02 kJ/mol and$\Delta$S° = 176.1 J/mol · K, at what temperature are reactants and products in their standard states at equilibrium?

Accepted Answer

$\Delta$G° = $\Delta$H° - T$\Delta$S° = 0 at equilibrium. Solving for T gives:T = $\Delta$H°/ $\Delta$S° = (58.02 kJ/mol)/(176.1 J/mol · K) = 329.5 K = +56.5°C

Question 19

The enthalpy and entropy of vaporization of ethanol are 38.6 kJ/mol and 109.8 J/mol · K, respectively. What is the boiling point of ethanol under equilibrium conditions, in °C?

Accepted Answer

The boiling point can be calculated using the formula ΔG = ΔH - TΔS = 0 at equilibrium. Solving for T gives T = ΔH/ΔS. Converting ΔH to J/mol (38,600 J/mol) and using ΔS = 109.8 J/mol·K, T = 38,600 / 109.8 = 351.64 K, which is approximately 78.5°C.

Question 20

Because the triple point of water is 273 K, what must be true of the change in enthalpy and the change in entropy for ice converting to water at this temperature?

Accepted Answer

The triple point is the temperature and pressure at which the solid, liquid, and gas phases of a substance coexist in equilibrium. At the triple point, the change in enthalpy ($\Delta$H) and the change in entropy ($\Delta$S) are both zero. Therefore, ($\Delta$H/$\Delta$S) = 0.

Quiz 18: Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

One of the following statements A-D may be incorrect. If so, identify it.

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

Which of the following must be true for a reaction to proceed to form products?

The entropy of vaporization of water is 109.0 J/mol · K. What is the enthalpy of vaporization of water at its normal boiling point?

A reaction with a low enthalpy of reaction value is not spontaneous at low temperature but becomes spontaneous at high temperature. What are the signs for $\Delta$ H° and $\Delta$ S°, respectively?

When a solution of DNA in water is heated, the double helix separates into two single strands. This process is called melting. What can be deduced from this information about the signs of the enthalpy and entropy changes for DNA melting?

At what temperature does the Fe(s) $\leftrightarrow$ Fe(g) phase transition occur? $\Delta$ H= 415.5 kJ/mol; $\Delta$ S = 153.4 J/mol · K.

Dinitrogen tetroxide (N₂O₄) decomposes to nitrogen dioxide (NO₂) . If $\Delta$ H° = 58.02 kJ/mol and $\Delta$ S° = 176.1 J/mol · K, at what temperature are reactants and products in their standard states at equilibrium?

The enthalpy and entropy of vaporization of ethanol are 38.6 kJ/mol and 109.8 J/mol · K, respectively. What is the boiling point of ethanol under equilibrium conditions, in °C?

Because the triple point of water is 273 K, what must be true of the change in enthalpy and the change in entropy for ice converting to water at this temperature?

Quiz 18: Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

One of the following statements A-D may be incorrect. If so, identify it.

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

Which of the following must be true for a reaction to proceed to form products?

The entropy of vaporization of water is 109.0 J/mol · K. What is the enthalpy of vaporization of water at its normal boiling point?

A reaction with a low enthalpy of reaction value is not spontaneous at low temperature but becomes spontaneous at high temperature. What are the signs for Δ\DeltaΔ H° and Δ\DeltaΔ S°, respectively?

When a solution of DNA in water is heated, the double helix separates into two single strands. This process is called melting. What can be deduced from this information about the signs of the enthalpy and entropy changes for DNA melting?

At what temperature does the Fe(s) ↔\leftrightarrow↔ Fe(g) phase transition occur? Δ\DeltaΔ H = 415.5 kJ/mol; Δ\DeltaΔ S = 153.4 J/mol · K.

Dinitrogen tetroxide (N2O4) decomposes to nitrogen dioxide (NO2) . If Δ\DeltaΔ H° = 58.02 kJ/mol and Δ\DeltaΔ S° = 176.1 J/mol · K, at what temperature are reactants and products in their standard states at equilibrium?

The enthalpy and entropy of vaporization of ethanol are 38.6 kJ/mol and 109.8 J/mol · K, respectively. What is the boiling point of ethanol under equilibrium conditions, in °C?

Because the triple point of water is 273 K, what must be true of the change in enthalpy and the change in entropy for ice converting to water at this temperature?

A reaction with a low enthalpy of reaction value is not spontaneous at low temperature but becomes spontaneous at high temperature. What are the signs for $\Delta$ H° and $\Delta$ S°, respectively?

At what temperature does the Fe(s) $\leftrightarrow$ Fe(g) phase transition occur? $\Delta$ H= 415.5 kJ/mol; $\Delta$ S = 153.4 J/mol · K.

Dinitrogen tetroxide (N₂O₄) decomposes to nitrogen dioxide (NO₂) . If $\Delta$ H° = 58.02 kJ/mol and $\Delta$ S° = 176.1 J/mol · K, at what temperature are reactants and products in their standard states at equilibrium?