CHM 1026 Kotz9e_TB_18_Entropy and Free Energy Questions With Verified Answers

Chapter 18—Entropy and Free Energy

1. When a chemical process occurs under standard conditions, which of the following conditions always
apply?
1. Gaseous species are at a pressure of 1 bar.
2. Solution concentrations species are 1 molal.
3. The temperature is 298.15 K.
a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3
2. Which of the following statements regarding the spontaneity of chemical and physical changes is correct?
a. A reaction may be spontaneous only in one direction.
b. A process can sometimes be spontaneous in the direction that moves it away from equilibrium.
c. Endothermic processes are never spontaneous.
d. A reactant favored process cannot be spontaneous.
e. Spontaneous changes occur only in the direction that leads to equilibrium.
3. Which of the following statements concerning entropy change is/are true?
1. For a reversible . process,
2. For a spontaneous process, .
3. For a reversible process, such as a phase change, ΔS =
qrev/T .
a. 1 only b. 2 only c. 3 only d. 2 and 3 e. 1, 2, and 3
4. The following processes occur spontaneously at 25 °C. Which of these processes is/are endothermic?
1. NH4NO3 dissolving in water (which is accompanied by a cooling of the water).
2. the expansion of a real gas into a vacuum (which is accompanied by a cooling of the gas).
3. liquid water in an ice cube tray freezing into ice after being placed in a freezer.
a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3
5. Which of the following statements is/are CORRECT?
1. Spontaneous changes only occur in the direction that leads to equilibrium.
2. Exothermic reactions are always spontaneous.
3. In any chemical reaction, energy must be conserved.
a. 1 only b. 2 only c. 3 only d. 1 and 3 e. 1, 2, and 3
6. For a certain reversible process q = 57.40 kJ at 36.6°C. What is ΔS for the process?
a. 0.185 J/K b. 185 J/K c. 1.57 J/K d. −0.185 J/K e. 2130 J/K
7. A statement of the first law of thermodynamics is that
a. in a spontaneous process, the entropy of the universe increases.
b. there is no disorder in a perfect crystal at 0 K.
c. the total energy of the universe is always decreasing.
d. the total energy of the universe is constant.
e. mass and energy are conserved in all chemical reactions.
8. The second law of thermodynamics states that
a. in a spontaneous process, the entropy of the universe increases.
b. there is no disorder in a perfect crystal at 0 K.
c. the total energy of the universe is always increasing.
d. the total energy of the universe is constant.
e. mass and energy are conserved in all chemical reactions.
9. What is the change in entropy for a system going from 189 possible microstates to 734 possible microstates?
(k = 1.381 × 10-23 J/K) a. 1.64× 10−22 J/K
b. 8.70× 10−23 J/K
c. −8.70× 10−23 J/K

, Kotz 9e Chapter 18 Entropy and Free Energy
d. 1.87× 10−23 J/K
e. −1.87× 10−23 J/K
10. Which of the following statements concerning entropy is not correct?
a. The entropy of a system increases as the number of available microstates increases.
b. The entropy of a system is proportional to the natural log of the number of microstates.
c. In a spontaneous process, ΔS(universe) indicates the extent to which energy is dispersed.
d. The dispersal of matter, such as the spontaneous expansion of a gas, cannot be explained by an increase
in entropy.
e. Entropy is a measure of the extent of energy dispersal.
11. As defined by Ludwig Boltzmann, the third law of thermodynamics states that
a. there is no disorder in a perfect crystal at 0 K.
b. in a spontaneous process, the entropy of the universe increases.
c. the total entropy of the universe is always increasing.
d. the total mass of the universe is constant.
e. mass and energy are conserved in all chemical reactions.
12. Which of the following statements concerning entropy is/are CORRECT?
1. The entropy of a substance increases when converted from a liquid to a solid.
2. The entropy of a substance decreases as its temperature increases.
3. All substances have positive entropy values at temperatures above 0 K.
a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3
13. Which of the following linear chain alcohols is likely to have the highest standard entropy in the liquid state?
a. CH3OH
b. CH3CH2OH
c. CH3CH2CH2OH
d. CH3CH2CH2CH2OH
e. CH3CH2CH2CH2CH2OH
14. If a chemical reaction occurs in a direction that has a positive change in entropy then
a. the change in enthalpy must be negative.
b. the reaction must be spontaneous.
c. heat goes from the system into the surroundings.
d. the reaction must be exothermic.
e. the disorder of the system increases.
15. Which of the following reactions would be expected to have a positive entropy change, ΔrS° > 0?
1. 2 SO2(g) + O2(g) → 2 SO3(g)
2. Ba(OH)2(s) → BaO(s) + H2O(g)
3. CO(g) + 2 H2(g) → CH3OH( )
a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1 and 3
16. Which of the following changes lead to a decrease in entropy?
a. the sublimation (vaporization) of dry ice (solid carbon dioxide)
b. sugar dissolving in coffee
c. evaporation of water from a lake
d. diffusion of perfume throughout a room
e. halving the volume of a gas

17. For which of the following reactions will the entropy of the system decrease?
a. 2 NH3(g) → N2(g) + 3 H2(g)
b. 2 C(s) + O2(g) → 2 CO(g)
c. CaCO3(s) → CaO(s) + CO2(g)