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Exam 18: Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

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Question 31

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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.

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Question 32

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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.

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Question 33

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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?

The equilibrium constant for a reaction is determined at several temperatures by measuring concentrations of reactants and products. To determine the standard enthalpy and entropy changes for the reactions, you need to plot ________ on the y-axis and ________ on the x-axis and fit the data to a linear equation. The slope of this line is equal to ________, and the intercept provides a value for ________.

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

When plotting ln K vs. 1/T, a linear relationship is obtained ________

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

If for a given chemical reaction at 298 K, the change in free energy, $\Delta$ G, is more negative than the change in the standard free energy, $\Delta$ G°, then ________

In a biochemical reaction, A + B $\Delta$ C with $\Delta$ G ^°rxn = 30 kJ/mol. Which of the following reactions might be effectively coupled to this reaction so that it becomes more spontaneous? I.C + D $\rightarrow$ B + E $\Delta$ G^°rxn = -40 kJ/mol II.C + D $\rightarrow$ B + E $\Delta$ G ^°rxn = +40 kJ/mol

The heat of fusion for water is 333.6 J/g. What is the entropy change for the universe when 1.00 L of water at 0°C freezes at -5°C? Comment on the sign.

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.

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

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

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 $\begin{array} { | c | c | c | c | } \hline \text { Parameter } & \mathbf { F e } & \mathbf { O } _ { 2 } & \mathrm { Fe } _ { 2 } \mathbf { O } _ { 3 } \\\hline & 0 & 0 & - 742 \\\Delta G _ { \mathrm { f } } ^ { \circ } & & & \\( \mathrm { kJ } / \mathrm { mol } ) & & & \\\hline &0 & 0& - 824 \\\Delta H _ { \mathrm { f } } ^ { \circ } & & & \\( \mathrm { kJ } / \mathrm { mol } ) & & & \\\hline & & & \\ S ^ { \circ } &27 &205 &87 \\ \mathrm { J } / ( \mathrm { mol } \cdot \mathrm { K } ) ] & & & \\\hline\end{array}$

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

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

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

Carbon monoxide has a very weak dipole moment. In the formation of solid carbon monoxide some molecules will be reversed in their orientation from C O - - - C O to C O - - - O C. What do you expect the absolute entropy of carbon monoxide solid to be at 0 K, and why?

If for a given chemical reaction at 298 K, the change in free energy, $\Delta$ G, is positive and the change in the standard free energy, $\Delta$ G°, is negative, then ________

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