Question 1

Which of the following statements best describes a spontaneous process in chemical thermodynamics?

Accepted Answer

A process that occurs without continuous energy input from outside the system.

Question 2

Consider the reaction: $$\mathrm{C_6H_{12}O_6$ (s) \rightarrow 2C_2H_5OH (l) + 2CO_2 (g)}. $$Predict the sign of the entropy change $$\Delta S$$ for this reaction.

Accepted Answer

Positive, because there is an increase in the number of gas molecules.

Question 3

Which law of thermodynamics states that the total entropy of the universe increases in any spontaneous process?

Accepted Answer

Second Law of Thermodynamics

Question 4

A chemical reaction has $$\Delta H  0. $$What can be said about its spontaneity at all temperatures?

Accepted Answer

It is spontaneous at all temperatures.

Question 5

Which of the following processes results in a decrease in entropy ($$\Delta S \u003c 0$$)?

Accepted Answer

Freezing of water

Question 6

Given the reaction $$\mathrm{N_2$ (g) + 3H_2 (g) \rightarrow 2NH_3 (g)}$$, calculate the standard entropy change $$\Delta S^\circ at 298 K $$using the following standard molar entropies: $$S^\circ(N_2$) = 191.5\ \mathrm{J/(mol\cdot K)}$$, $$S^\circ(H_2$) = 130.6\ \mathrm{J/(mol\cdot K)}$$, $$S^\circ(NH_3$) = 192.3\ \mathrm{J/(mol\cdot K)}.$$

Accepted Answer

$$\Delta S^\circ = -198.7\ \mathrm{J/(mol\cdot K)}$$

Question 7

Which equation correctly relates Gibbs free energy ($$\Delta G$$), enthalpy ($$\Delta H$$), and entropy ($$\Delta S) $$for a process at constant temperature?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 8

A reaction is endothermic ($$\Delta H \u003e 0) $$and results in an increase in entropy ($$\Delta S \u003e 0). $$Under what conditions will this reaction be spontaneous?

Accepted Answer

At high temperatures

Question 9

Which of the following best explains why the condensation of water vapor is spontaneous at room temperature, even though the entropy of the system decreases?

Accepted Answer

The process is exothermic, and the heat released increases the entropy of the surroundings.

Question 10

Which of the following statements about entropy ($$S) is $$correct?

Accepted Answer

Entropy is a measure of disorder or randomness in a system.

Question 11

A process occurs at constant pressure and temperature, releasing heat to the surroundings. How does the entropy of the surroundings change?

Accepted Answer

It increases.

Question 12

Which of the following is true for a reversible process?

Accepted Answer

$$\Delta S_{univ} = 0$$

Question 13

Which of the following changes will always increase the entropy of a system?

Accepted Answer

Increasing the volume

Question 14

The third law of thermodynamics states that the entropy of a perfect crystal at absolute zero is:

Accepted Answer

Zero

Question 15

Which of the following reactions is most likely to have a positive entropy change ($$\Delta S \u003e 0$$)?

Accepted Answer

$$\mathrm{$$CaCO_3$$ (s) \rightarrow CaO (s) + CO_2$ (g)}$$

Question 16

Which of the following best describes the relationship between the number of microstates and entropy?

Accepted Answer

More microstates correspond to higher entropy.

Question 17

For the reaction $$\mathrm{CH_3OH (g) + H_2O (g) \rightarrow CO_2$ (g) + 3H_2 (g)}$$, given the following standard molar entropies: $$S^\circ(CH_3OH) = 239.9\ \mathrm{J/(mol\cdot K)}$$, $$S^\circ(H_2O) = 188.7\ \mathrm{J/(mol\cdot K)}$$, $$S^\circ(CO_2$) = 213.8\ \mathrm{J/(mol\cdot K)}$$, $$S^\circ(H_2$) = 130.6\ \mathrm{J/(mol\cdot K)}$$, calculate $$\Delta S^\circ$$ for the reaction.

Accepted Answer

$$\Delta S^\circ = 176.9\ \mathrm{J/(mol\cdot K)}$$

Question 18

Which of the following is the correct expression for the entropy change of the surroundings ($$\Delta S_{surr}) $$for a process at constant pressure and temperature?

Accepted Answer

$$\Delta S_{surr} = \dfrac{q_{sys}}{T}$$

Question 19

A reaction has $$\Delta H \u003e 0$$ and $$\Delta S \u003c 0. $$What can be said about its spontaneity?

Accepted Answer

It is never spontaneous.

Lecture Slides Chapter 12

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