Question 1

Which of the following best describes the concept of entropy as illustrated by the image of a disordered pile of playing cards?

Accepted Answer

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

Question 2

According to the second law of thermodynamics, which of the following statements is true?

Accepted Answer

The entropy of the universe is constantly increasing.

Question 3

Which process would result in a negative entropy change ($$\Delta S \u003c 0$$)?

Accepted Answer

Water vapor condensing to form liquid water.

Question 4

Given the reaction: $$2SO_2(g) + O_2$(g) \rightarrow 2SO_3(g)$$, and the following standard molar entropies: $$SO_2(g$$): 248.1\ J/K\cdot mol$$, O_2$(g): 205.3\ J/K\cdot mol$$, $$SO_3(g$$): 256.6\ J/K\cdot mol$$, calculate $$\Delta S^\circ_{rxn}$$ at 25°C.

Accepted Answer

$$-188.3\ J/K$$

Question 5

Which of the following scenarios would result in the greatest increase in entropy?

Accepted Answer

$$CO_2(s$$) \rightarrow $$CO_2(g$$)$$

Question 6

For the reaction $$Sb_2S_3(s) + 3Fe(s) \rightarrow 2Sb(s) + 3FeS(s)$$ with $$\Delta H = -125\ kJ at 25$$°C, what is $$\Delta S_{surr}$$?

Accepted Answer

$$-2.61 	imes 10^3$\ J/K$$

Question 7

Which of the following is true regarding the spontaneity of a reaction?

Accepted Answer

A reaction is spontaneous if $$\Delta G is $$negative.

Question 8

Calculate the temperature at which water boils thermodynamically, given $$\Delta H_{vap} = 44\ kJ$$ and $$\Delta S_{vap} = 118.8\ J/K.$$

Accepted Answer

$$370\ K$$

Question 9

Which equation correctly relates the standard free energy change to the equilibrium constant $$K$$?

Accepted Answer

$$\Delta G^\circ = -RT\ln K$$

Question 10

For the reaction $$C_{diamond}(s) \rightarrow C_{graphite}(s)$$, given $$\Delta G^\circ$$ for $$C_{diamond}(s) + O_2$(g) \rightarrow CO_2$(g) is$$ $$-397\ kJ$$ and for $$C_{graphite}(s) + O_2$(g) \rightarrow CO_2$(g) is$$ $$-394\ kJ$$, what is $$\Delta G^\circ$$ for the conversion?

Accepted Answer

$$-3\ kJ$$

Question 11

Which of the following best explains why a highly exothermic reaction can be spontaneous even if the system's entropy decreases?

Accepted Answer

The large negative $$\Delta H$$ increases the entropy of the surroundings enough to make $$\Delta S_{universe}$$ positive.

Question 12

Which of the following is the correct formula for calculating the entropy change for a reversible phase change at constant temperature?

Accepted Answer

$$\Delta S = \frac{q}{T}$$

Question 13

Which of the following conditions will always result in a nonspontaneous reaction?

Accepted Answer

$$\Delta H \u003e 0$$ \, and \, \Delta S \u003c 0$

Question 14

A battery is used to do work by sending current to a starter motor, as shown in the diagram. Which thermodynamic concept does this best illustrate?

Accepted Answer

The maximum work a system can do at constant temperature and pressure is equal to $$\Delta G.$$

Question 15

Which of the following best describes the relationship between $$\Delta G$$ and the equilibrium constant $$K$$?

Accepted Answer

$$\Delta G  1$$

Question 16

Which of the following is NOT a factor that increases the entropy of a system?

Accepted Answer

A gas condensing to a liquid.

Question 17

Which equation would you use to calculate the free energy change for a reaction under non-standard conditions?

Accepted Answer

$$\Delta G = \Delta G^\circ + RT\ln Q$$

Question 18

Which of the following best explains why the entropy of a perfect crystal at 0 K is zero?

Accepted Answer

There is only one possible arrangement of the particles.

Question 19

Which of the following best describes the significance of the graphs showing free energy versus fraction of A reacted?

Accepted Answer

Equilibrium occurs at the minimum value of free energy.

Thermodynamics: Entropy, Free Energy, and Spontaneity

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