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Problem 11

Which of these processes are spontaneous? (a) A satellite falls to Earth. (b) Water decomposes to $\mathrm{H}_{2}$ and $\mathrm{O}_{2}$ at 298 $\mathrm{K}$ and 1 $\mathrm{atm} .(\mathrm{c})$ Average car prices increase.

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## Discussion

## Video Transcript

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## Recommended Questions

Which of the following processes are spontaneous?

a. A house is built.

b. A satellite is launched into orbit.

c. A satellite falls back to the earth.

d. The kitchen gets cluttered.

Which of the following processes are spontaneous?

a. A house is built.

b. A satellite is launched into orbit.

c. A satellite falls back to earth.

d. The kitchen gets cluttered.

Which of these processes are spontaneous? (a) Water evaporates from a puddle. (b) A lion chases an antelope. (c) An isotope undergoes radioactive disintegration.

Which of the following processes is/are spontaneous?

a. A hurricane forms.

b. A corpse decomposes.

c. You get an $A$ in this course.

d. Ice cream melts on a hot summer day.

Which of these processes are spontaneous? (a) Earth moves around the Sun. (b) A boulder rolls up a hill. (c) Sodium metal and chlorine gas form solid sodium chloride.

Which of the following processes are spontaneous, and which are nonspontaneous?

(a) Freezing of water at $2^{\circ} \mathrm{C}$

(b) Corrosion of iron metal

(c) Expansion of a gas to fill the available volume

(d) Separation of an unsaturated aqueous solution of potassium chloride into solid $\mathrm{KCl}$ and liquid water

Identify the following processes as either spontaneous or not spontaneous.

(a) Ice melts when placed in a flask containing water at $5^{\circ} \mathrm{C}.$

(b) Hydrogen iodide molecules decompose at $400 \mathrm{K}$ to give a mixture of $\mathrm{H}_{2}, \mathrm{I}_{2},$ and $\mathrm{HI}$

(c) Ethanol and water are mixed to form a solution.

(d) Slightly soluble $\mathrm{PbCl}_{2}\left(K_{\mathrm{sp}}=1.7 \times 10^{-5}\right)$ dissolves in water to form a saturated solution.

Which of these processes is spontaneous?

a. the combustion of natural gas

b. the extraction of iron metal from iron ore

c. a hot drink cooling to room temperature

d. drawing heat energy from the ocean's surface to power a ship

Which of the following processes are spontaneous and which are nonspontaneous: (a) the ripening of a banana, (b) dissolution of sugar in a cup of hot coffee, (c) the reaction of nitrogen atoms to form $\mathrm{N}_{2}$ molecules at $25^{\circ} \mathrm{C}$ and $1 \mathrm{atm},(\mathbf{d})$ lightning, (e) formation of $\mathrm{CH}_{4}$ and $\mathrm{O}_{2}$ molecules from $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ at room temperature and 1 atm of pressure?

Which of these processes is spontaneous?

\begin{equation}\begin{array}{l}{\text { a. the combustion of natural gas }} \\ {\text { b. the extraction of iron metal from iron ore }} \\ {\text { c. a hot drink cooling to room temperature }} \\ {\text { d. drawing heat energy from the ocean's surface to power a ship }}\end{array}\end{equation}

Which of these processes are spontaneous? (a) Methane burns in air. (b) A teaspoonful of sugar dissolves in a cup of hot coffee. (c) A soft-boiled egg becomes raw.

Which of the following processes is/are spontaneous?

a. Wood burns in air.

b. Water vapor condenses on the sides of a glass of iced tea.

c. Salt dissolves in water.

d. Photosynthesis.

Which of the following processes are spontaneous: (a) the melting of ice cubes at $-10^{\circ} \mathrm{C}$ and 1 atm pressure; (b) separating a mixture of $\mathrm{N}_{2}$ and $\mathrm{O}_{2}$ into two separate samples, one that is pure $\mathrm{N}_{2}$ and one that is pure $\mathrm{O}_{2}$;(c) alignment of iron filings in a magnetic field; (d) the reaction of hydrogen gas with oxygen gas to form water vapor at room temperature; (e) the dissolution of HCl(g) in water to form concentrated hydrochloric acid?

Determine which of the following suggested decays can occur spontaneously:

(a) $_{20}^{40} \mathrm{Ca} \rightarrow \mathrm{c}^{+}+_{19}^{40} \mathrm{K}$ (b) $_{60}^{144} \mathrm{Nd} \rightarrow_{2}^{4} \mathrm{He}+\stackrel{140}{58} \mathrm{Ce}$

Which of these reactions would you expect to be spontaneous at relatively high temperatures? At relatively low temperatures? Explain.

$$

\begin{array}{l}{\text { a. } \mathrm{CH}_{3} \mathrm{OH}(1) \rightarrow \mathrm{CH}_{3} \mathrm{OH}(\mathrm{g})} \\ {\text { b. } \mathrm{CH}_{3} \mathrm{OH}(\mathrm{g}) \rightarrow \mathrm{CH}_{3} \mathrm{OH}(1)} \\ {\text { c. } \mathrm{CH}_{3} \mathrm{OH}(\mathrm{s}) \rightarrow \mathrm{CH}_{3} \mathrm{OH}(1)}\end{array}

$$

Determine whether each of the following reactions is spontaneous.

a. $\Delta H_{\text { system }}=-75.9 \mathrm{kJ}, T=273 \mathrm{K}, \Delta S_{\text { system }}=138 \mathrm{J} / \mathrm{K}$

b. $\Delta \mathrm{H}_{\text { system }}=-27.6 \mathrm{kJ}, T=535 \mathrm{K}, \Delta S_{\text { system }}=-55.2 \mathrm{J} / \mathrm{K}$

c. $\Delta H_{\text { system }}=365 \mathrm{kJ}, T=388 \mathrm{K}, \Delta S_{\mathrm{system}}=-55.2 \mathrm{J} / \mathrm{K}$

d. $\Delta H_{\mathrm{system}}=452 \mathrm{kJ}, T=165 \mathrm{K}, \Delta S_{\mathrm{system}}=55.7 \mathrm{J} / \mathrm{K}$

Which of the following processes are spontaneous and which are nonspontaneous? (a) dissolving table salt (NaCl) in hot soup; (b) climbing Mt. Everest; (c) spreading fragrance in a room by removing the cap from a perfume bottle; (d) separating helium and neon from a mixture of the gases

Indicate whether the following processes are spontaneous or nonspontaneous.

(a) Liquid water freezing at a temperature below its freezing point

(b) Liquid water freezing at a temperature above its freezing point

(c) The combustion of gasoline

(d) A ball thrown into the air

(e) A raindrop falling to the ground

(f) Iron rusting in a moist atmosphere

Indicate whether the following processes are spontaneous or nonspontaneous:

(a) Heat transfer from a block of ice to a room maintained at $25^{\circ} \mathrm{C}$

(b) Evaporation of water from an open beaker

(c) Conversion of iron(III) oxide to iron metal and oxygen

(d) Uphill motion of an automobile

Which of these processes are nonspontaneous? Are thenonspontaneous processes impossible?

\begin{equation}\begin{array}{l}{\text { a. a bike going up a hill }} \\ {\text { b. a meteor falling to Earth }} \\ {\text { c. obtaining hydrogen gas from liquid water }} \\ {\text { d. a ball rolling down a hill }}\end{array}\end{equation}

Which of the following processes are spontaneous? Which are nonspontaneous?

(a) Diffusion of perfume molecules from one side of a room to the other

(b) Heat flow from a cold object to a hot object

(c) Decomposition of rust $\left(\mathrm{Fe}_{2} \mathrm{O}_{3} \cdot \mathrm{H}_{2} \mathrm{O}\right)$ to iron metal, oxygen, and water

(d) Decomposition of solid $\mathrm{CaCO}_{3}$ to solid CaO and gaseous $\mathrm{CO}_{2}$ at $25^{\circ} \mathrm{C}$ and 1 atm pressure $\left(K_{\mathrm{p}}=1.4 \times 10^{-23}\right)$

Which of the following reactions is spontaneous (i) only at low temperatures; (ii) only at high temperatures; (iii) at all temperatures?

a. $2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{NO}_{2}(g)$

b. $2 \mathrm{NH}_{3}(g)+2 \mathrm{O}_{2}(g) \rightarrow \mathrm{N}_{2} \mathrm{O}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)$

c. $\mathrm{NH}_{4} \mathrm{NO}_{3}(s) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(g)+\mathrm{N}_{2} \mathrm{O}(g)$

Which of these processes are nonspontaneous? Are the nonspontaneous processes impossible?

a. a bike going up a hill

b. a meteor falling to Earth

c. obtaining hydrogen gas from liquid water

d. a ball rolling down a hill

Tell whether the following processes are spontaneous or nonspontaneous:

(a) Dissolving sugar in hot coffee

(b) Decomposition of NaCl to solid sodium and gaseous chlorine at $25^{\circ} \mathrm{C}$ and 1 atm pressure

(c) Uniform mixing of bromine vapor and nitrogen gas

(d) Boiling of gasoline at $25^{\circ} \mathrm{C}$ and 1 atm pressure

For a certain chemical reaction, $\Delta H^{\circ}=-35.4 \mathrm{kJ}$ and $\Delta S^{\circ}=-85.5 \mathrm{J} / \mathrm{K}$ . (a) Is the reaction exothermic or endothermic? (b) Does the reaction lead to an increase or decrease in the randomness or disorder of the system?(c) Calculate $\Delta G^{\circ}$ for the reaction at 298 $\mathrm{K}$ . (d) Is the reaction spontaneous at 298 $\mathrm{K}$ under standard conditions?

Explain what is meant by a spontaneous process. Give two examples each of spontaneous and nonspontaneous processes.

Which process is spontaneous at 298 K?

a. H2O(l)-H2O(g, 1 atm)

b. H2O(l)-H2O(g, 0.10 atm)

c. H2O(l)-H2O(g, 0.010 atm)

At $1500 \mathrm{K},$ the process $$\begin{aligned} &\mathbf{I}_{2}(g) \longrightarrow 2 \mathbf{I}(g)\\ &10 \mathrm{atm} \quad 10 \mathrm{atm} \end{aligned}$$ is not spontaneous. However, the process $$\begin{aligned} &\mathbf{I}_{2}(g) \longrightarrow 2 \mathbf{I}(g)\\ &0.10 \mathrm{atm} \quad 0.10 \mathrm{atm} \end{aligned}$$ is spontaneous at $1500 \mathrm{K}$. Explain.

Which of the following processes are spontaneous?

a. Salt dissolves in $\mathrm{H}_{2} \mathrm{O}$ .

b. A clear solution becomes a uniform color after a few drops of dye are added.

c. Iron rusts.

d. You clean your bedroom.

Which of the following reactions are spontaneous under standard conditions at $25^{\circ} \mathrm{C},$ and which are nonspontaneous?

$$

\begin{array}{l}{\text { (a) } \mathrm{AgNO}_{3}(a q)+\mathrm{NaCl}(a q) \longrightarrow \mathrm{AgCl}(s)+\mathrm{NaNO}_{3}(a q) \quad \Delta G^{\circ}=-55.7 \mathrm{kJ}} \\ {\text { (b) } 2 \mathrm{C}(s)+2 \mathrm{H}_{2}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{4}(g) \quad \Delta G^{\circ}=68.1 \mathrm{kJ}}\end{array}

$$

Which of the following events is not followed by primary succession?

a. A glacier recedes.

b. A volcano erupts.

c. A fire destroys a forest.

d. A hurricane creates a bare-sand beach.

e. All of these disturbances are followed by primary succession.

What is a spontaneous process? Provide an example.

What is a spontaneous process? Provide an example.

A certain reaction has $\Delta H^{\circ}=+23.7 \mathrm{kJ}$ and $\Delta S^{\circ}=$ $+52.4 \mathrm{J} / \mathrm{K}$ . (a) Is the reaction exothermic or endothermic? (b) Does the reaction lead to an increase or decrease in the randomness or disorder of the system?(c) Calculate $\Delta G^{\circ}$ for the reaction at 298 $\mathrm{K}$ . (d) Is the reaction spontaneous at 298 $\mathrm{K}$ under standard conditions?

At what temperatures will the following processes be spontaneous?

a. $\Delta H=-18 \mathrm{kJ}$ and $\Delta S=-60 . \mathrm{J} / \mathrm{K}$

b. $\Delta H=+18 \mathrm{kJ}$ and $\Delta S=+60 . \mathrm{J} / \mathrm{K}$

c. $\Delta H=+18 \mathrm{kJ}$ and $\Delta S=-60 . \mathrm{J} / \mathrm{K}$

d. $\Delta H=-18 \mathrm{kJ}$ and $\Delta S=+60 . \mathrm{J} / \mathrm{K}$

Which process is necessarily driven by an increase in the entropy of the surroundings?

\begin{equation}\begin{array}{l}{\text { a. the condensation of water }} \\ {\text { b. the sublimation of dry ice }} \\ {\text { c. the freezing of water }}\end{array}\end{equation}

At what temperatures will the following processes be spontaneous?

a. $\Delta H=-18 \mathrm{kJ}$ and $\Delta S=-60 . \mathrm{J} / \mathrm{K}$

b. $\Delta H=+18 \mathrm{kJ}$ and $\Delta S=+60 . \mathrm{JK}$

c. $\Delta H=+18 \mathrm{kJ}$ and $\Delta S=-60 . \mathrm{J} / \mathrm{K}$

d. $\Delta H=-18 \mathrm{kJ}$ and $\Delta S=+60 . \mathrm{J} / \mathrm{K}$

(a) Does the entropy of the surroundings increase for spontaneous processes? (b) In a particular spontaneous process the entropy of the system decreases. What can you conclude about the sign and magnitude of $\Delta S_{\text { surr. }} ?(\mathbf{c})$ During a certain reversible process, the surroundings undergo an entropy change, $\Delta S_{\text { surr }}=-78 \mathrm{J} / \mathrm{K}$ . What is the entropy change of the system for this process?

Which process is necessarily driven by an increase in the entropy of the surroundings?

a. the condensation of water

b. the sublimation of dry ice

c. the freezing of water

In which of the following reactions or decays is strangeconserved? In each case, explain your reasoning. (a) $\mathrm{K}^{+} \rightarrow$ $\mu^{+}+\nu_{\mu} ;(\mathrm{b}) \mathrm{n}+\mathrm{K}^{+} \rightarrow \mathrm{p}+\pi^{0} ;(\mathrm{c}) \mathrm{K}^{+}+\mathrm{K}^{-} \rightarrow \pi^{0}+\pi^{0} ;(\mathrm{d}) \mathrm{p}+$ $\mathrm{K}^{-} \rightarrow \Lambda^{0}+\pi^{0} .$

The reaction, $$2 \mathrm{Cl}_{2} \mathrm{O}(\mathrm{g}) \longrightarrow 2 \mathrm{Cl}_{2}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g})$$ $$\Delta_{r} H^{\circ}=$$ $-161 \mathrm{kJmol}^{-1},$ is expected to be (a) spontaneous at all temperatures; (b) spontaneous at low temperatures, but nonspontaneous at high temperatures;

(c) nonspontaneous at all temperatures; (d) spontaneous at high temperatures only.

Predict whether each of the following processes results in an increase in entropy in the system. (Define reactants and products as the system.)

(a) Water vapor condenses to liquid water at $90^{\circ} \mathrm{C}$ and 1 atm pressure.

(b) The exothermic reaction of $\mathrm{Na}(\mathrm{s})$ and $\mathrm{Cl}_{2}(\mathrm{g})$ forms $\mathrm{NaCl}(\mathrm{s})$

(c) The endothermic reaction of $\mathrm{H}_{2}$ and $\mathrm{I}_{2}$ produces an equilibrium mixture of $\mathrm{H}_{2}(\mathrm{g})$ $\mathrm{I}_{2}(\mathrm{g}),$ and $\mathrm{HI}(\mathrm{g})$

(d) Solid NaCl dissolves in water forming a saturated solution.

Calculate the standard free-energy change of the following reaction. Is it spontaneous?

$$2 \mathrm{NO}(g)+2 \mathrm{H}_{2}(g) \rightarrow \mathrm{N}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(g)$$

The spontaneous reaction $A \rightarrow B+C$ increases the system entropy by $72.0 \mathrm{J} / \mathrm{K} .$ What is the minimum value of the entropy change of the surroundings?

From the values of $\Delta H$ and $\Delta S$, predict which of the following reactions would be spontaneous at $25^{\circ} \mathrm{C}$ : reaction $\mathrm{A}$ : $\Delta H=10.5 \mathrm{kJ} / \mathrm{mol}, \Delta S=30 \mathrm{J} / \mathrm{K} \cdot \mathrm{mol} ;$ reaction $\mathrm{B}: \Delta H=$ $1.8 \mathrm{kJ} / \mathrm{mol}, \Delta S=-113 \mathrm{J} / \mathrm{K} \cdot$ mol. If either of the reactions is nonspontaneous at $25^{\circ} \mathrm{C},$ at what temperature might it become spontaneous?

(II) A falling rock has kinetic energy $\small\mathrm{KE}$ just before striking the ground and coming to rest. What is the total change in entropy of rock plus environment as a result of this collision?

Of the four processes that shape the surface of a terrestrial world, the one with the greatest potential for catastrophic rearrangement is

a. impact cratering.

b. volcanism.

c. tectonism.

d. erosion.

In which of the following reactions or decays is strangeness conserved? In each case, explain your reasoning. (a) $K^+ \rightarrow \mu^+ + \nu_\mu$; (b) $n + K^+ \rightarrow p + \pi^0$; (c) $K^+ + K^- \rightarrow \pi^0 + \pi^0$; (d) $p + K^- \rightarrow \Lambda^0 + \pi^0$.

Indicate whether each of the following changes represents an increase or a decrease in entropy in a system, and explain your reasoning: (a) the freezing of ethanol; (b) the sublimation of dry ice; (c) the burning of a rocket fuel.

Predict the mode(s) of decay of the following radionuclides:

(a) $^{24} \mathrm{Ne} ;$ (b) $^{38} \mathrm{K} ;(\mathrm{c})^{45} \mathrm{Ti} ;(\mathrm{d})^{237} \mathrm{Np}$

Consider the following facts: Water freezes spontaneously at $-5^{\circ} \mathrm{C}$ and $1 \mathrm{atm},$ and ice has a more ordered structure than liquid water. Explain how a spontaneous process can lead to a decrease in entropy.

Forces that cause geologic change include _______________(select all that are correct).

a. movement of water

b. natural selection

c. volcanic activity

d. tectonic plate movement

e. wind

f. asteroid impacts

Predict the sign of the entropy change for the following processes.

(a) An ice cube is warmed to near its melting point.

(b) Exhaled breath forms fog on a cold morning.

(c) Snow melts.

What type of decay process is involved in each of the following?

a. $_{92}^{228} \mathrm{U} \rightarrow_{91}^{228} \mathrm{Pa}+(?)$

b.$_{100} ^{254}\mathrm {Fm} \rightarrow_{98}^{250} \mathrm{gg}$ Cf $+(?)$

List these in order of increasing entropy: (a) $0.5 \mathrm{kg}$ of ice and $0.5 \mathrm{kg}$ of (liquid) water at $0^{\circ} \mathrm{C} ;$ (b) $1 \mathrm{kg}$ of ice at $0^{\circ} \mathrm{C} ;$ (c) $1 \mathrm{kg}$ of (liquid) water at $0^{\circ} \mathrm{C} ;$ (d) $1 \mathrm{kg}$ of water at $20^{\circ} \mathrm{C}$.

\begin{equation}

\begin{array}{l}{\text { Which of these processes are nonspontaneous? Are the nonspontane- }} \\ {\text { ous processes impossible? }} \\ {\text { a. a bike going up a hill }} \\ {\text { b. a meteor falling to Earth }} \\ {\text { c. obtaining hydrogen gas from liquid water }} \\ {\text { d. a ball rolling down a hill }}\end{array}

\end{equation}

Predict whether each of the following processes results in an increase in entropy in the system. (Define reactants and products as the system.)

(a) Water vapor condenses as dew (liquid water) at $0^{\circ} \mathrm{C}$ and 1 atm pressure.

(b) An exothermic reaction of $\mathrm{Al}(\mathrm{s})$ and $\mathrm{Br}_{2}(\ell)$ forms $\mathrm{Al}_{2} \mathrm{Br}_{6}(\mathrm{s})$

(c) The endothermic decomposition of solid $\mathrm{CaCO}_{3}$ at $800^{\circ} \mathrm{C}$ to produce an equilibrium mixture containing solid $\mathrm{CaCO}_{3},$ solid $\mathrm{CaO}$ and gaseous $\mathrm{CO}_{2}$

(d) One mol of AgCl(s) decomposes, forming 1.0 mole of $\mathrm{Ag}(\mathrm{s})$ and $0.5 \mathrm{mol} \mathrm{Cl}_{2}(\mathrm{g})$

Which of the following changes in a thermodynamic property would you expect to find for the reaction $\mathrm{Br}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{Br}(\mathrm{g})$ at all temperatures? Explain. (a)

$\Delta H<0 ;(\mathbf{b}) \Delta S>0 ;(\mathrm{c}) \Delta G<0 ;$ (d) $\Delta S<0$.

A reaction that occurs in the internal combustion engine is

$$\mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{NO}(g)$$

(a) Determine $\Delta H^{\circ}$ and $\Delta S^{\circ}$ for the reaction at 298 $\mathrm{K}$ .

(b) Assuming that these values are relatively independent of temperature, calculate $\Delta G^{\circ}$ at $100 .^{\circ} \mathrm{C}, 2560 .^{\circ} \mathrm{C},$ and $3540 .^{\circ} \mathrm{C} .$

(c) What is the significance of the different values of $\Delta G^{\circ} ?$

(d) At what temperature (in $\mathrm{K} )$ does the reaction become spontaneous?

Which of the following processes would not result in an entropy increase for the indicated system?

a. Melting of an ice cube

b. Evaporation of a sample of an alcohol

c. Sublimation of a mothball

d. Cooling of hot water to room temperature

From the values given for $\Delta H^{\circ}$ and $\Delta S^{\circ},$ calculate $\Delta G^{\circ}$ for

each of the following reactions at 298 $\mathrm{K}$ . If the reaction is not spontaneous under standard conditions at 298 $\mathrm{K}$ , at what temperature (if any) would the reaction become

spontaneous?

$$

\begin{array}{l}{\text { (a) } 2 \mathrm{PbS}(s)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{PbO}(s)+2 \mathrm{SO}_{2}(g)} \\ {\Delta H^{\circ}=-844 \mathrm{kk} ; \Delta S^{\circ}=-165 \mathrm{J} / \mathrm{K}} \\ {\text { (b) } 2 \mathrm{POCl}_{3}(g) \longrightarrow 2 \mathrm{PCl}_{3}(g)+\mathrm{O}_{2}(g)} \\ {\Delta H^{\circ}=572 \mathrm{kJ} ; \Delta S^{\circ}=179 \mathrm{J} / \mathrm{K}}\end{array}

$$

What process takes place in each situation? (Chapter 12$)$

a. a solid air-freshener cube getting smaller and smaller

b. dewdrops forming on leaves in the morning

c. steam rising from a hot spring

d. a crust of ice forming on top of a pond

Which of the following reactions occur spontaneously, and which can be brought about only through electrolysis, assuming that all reactants and products are in their standard states? For those requiring electrolysis, what is the minimum voltage required?

(a) $2 \mathrm{H}_{2} \mathrm{O}(1) \longrightarrow 2 \mathrm{H}_{2}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g})\left[\operatorname{in} 1 \mathrm{M} \mathrm{H}^{+}(\mathrm{aq})\right]$

(b) $\mathrm{Zn}(\mathrm{s})+\mathrm{Fe}^{2+}(\mathrm{aq}) \longrightarrow \mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{Fe}(\mathrm{s})$

(c) $2 \mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{I}_{2}(\mathrm{s}) \longrightarrow 2 \mathrm{Fe}^{3+}(\mathrm{aq})+2 \mathrm{I}^{-}(\mathrm{aq})$

(d) $\mathrm{Cu}(\mathrm{s})+\mathrm{Sn}^{4+}(\mathrm{aq}) \longrightarrow \mathrm{Cu}^{2+}(\mathrm{aq})+\mathrm{Sn}^{2+}(\mathrm{aq})$

\begin{equation}

\begin{array}{l}{\text { Which of thesc processes is spontaneous? }} \\ {\text { a. the combustion of natural gas }} \\ {\text { b. the extraction of iron metal from iron ore }} \\ {\text { c. a hot drink cooling to room temperature }} \\ {\text { d. drawing heat energy from the ocean's surface to power a ship }}\end{array}

\end{equation}

Which statement is true?

a. A spontaneous reaction is always a fiast reaction.

b. A spontaneous reaction is always a slow reaction.

c. The spontaneity of a reaction is not necessarily related to the speed

of a reaction.

Calculate $\Delta G_{\text { system }}$ for each process, and state whether

the process is spontaneous or nonspontaneous.

a. $\Delta H_{\text { system }}=145 \mathrm{kJ}, T=293 \mathrm{K}, \Delta S_{\mathrm{system}}=195 \mathrm{J} / \mathrm{K}$

b. $\Delta H_{\text { system }}=-232 \mathrm{kJ}, T=273 \mathrm{K}, \Delta S_{\mathrm{system}}=138 \mathrm{J} / \mathrm{K}$

c. $\Delta H_{\mathrm{system}}=-15.9 \mathrm{kJ}, T=373 \mathrm{K}, \Delta S_{\mathrm{system}}=-268 \mathrm{J} / \mathrm{K}$

A reaction has $\Delta H_{298}^{\circ}=100 \mathrm{kJ} / \mathrm{mol}$ and $\Delta S_{298}^{\mathrm{o}}=250 \mathrm{J} / \mathrm{mol}$ . Is the reaction spontaneous at room temperature? If not, under what temperature conditions will it become spontaneous?

Which statement is true?

a. A reaction in which the entropy of the system increases can be spontaneous only if it is exothermic.

b. A reaction in which the entropy of the system increases can be spontaneous only if it is endothermic.

c. A reaction in which the entropy of the system decreases can be spontaneous only if it is exothermic.

Which of the following is not a major problem with the damming of rivers?

a. increase in salinity

b. loss of water through evaporation

c. change in the level of the water table

d. buildup of sediment

A 70.0 -kg log falls from a height of 25.0 $\mathrm{m}$ into a lake. If the log, the lake, and the air are all at $300 . \mathrm{K}$ , find the change in entropy of the Universe during this process.

Which of the reactions (a) $-(\mathrm{d})$ in Problem 8.102 are spontaneous at all temperatures, which are nonspontaneous at all temperatures, and which have an equilibrium temperature?

In which of the following reactions is entropy increasing?

(A) $2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{SO}_{3}(g)$ (B) $\mathrm{CO}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{H}_{2}(g)+\mathrm{CO}_{2}(g)$

(C) $\mathrm{H}_{2}(g)+\mathrm{Cl}_{2}(g) \rightarrow 2 \mathrm{HCl}(g)$

(D) $2 \mathrm{NO}_{2}(g) \rightarrow 2 \mathrm{NO}(g)+\mathrm{O}_{2}(g)$

Forces that cause geologic change do not include ________.

a. erosion

b. natural selection

c. volcanic activity

d. tectonic plate movement

e. wind

f. meteorite impacts

Predict by what mode(s) of spontaneous radioactive decay each of the following unstable isotopes might proceed:

(a) $_{2}^{6} \mathrm{He}$

(b) 60 $\mathrm{Zn}$

(c) $\frac{235}{91} \mathrm{Pa}$

(d) 241

(e) $^{18} \mathrm{F}$

Tell whether reactions with the following values of $\Delta H$ and $\Delta S$ are spontaneous or nonspontaneous and whether they are exothermic or endothermic:

$$

\begin{array}{l}{\text { (a) } \Delta H=-128 \mathrm{kJ} ; \Delta S=35 \mathrm{J} / \mathrm{K} \text { at } 500 \mathrm{K}} \\ {\text { (b) } \Delta H=+67 \mathrm{kJ} ; \Delta S=-140 \mathrm{J} / \mathrm{K} \text { at } 250 \mathrm{K}} \\ {\text { (c) } \Delta H=+75 \mathrm{kJ} ; \Delta S=95 \mathrm{J} / \mathrm{K} \text { at } 800 \mathrm{K}}\end{array}

$$

Which of the following processes are exothermic, and which are endothermic? (a) frost forms on a car window in the winter; (b) water condenses on a glass of ice water on a humid summer afternoon; (c) adding ammonium nitrate to water causes the temperature of the solution to decrease.

Arrange the entropy changes of the following processes, all at $25^{\circ} \mathrm{C}$, in the expected order of increasing $\Delta S,$ and explain your reasoning:

(a) $\mathrm{H}_{2} \mathrm{O}(\mathrm{l}, 1 \mathrm{bar}) \longrightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{g}, 1 \mathrm{bar})$

(b) $\mathrm{CO}_{2}(\mathrm{s}, 1 \mathrm{bar}) \longrightarrow \mathrm{CO}_{2}(\mathrm{g}, 0.01 \mathrm{bar})$

(c) $\mathrm{H}_{2} \mathrm{O}(1,1 \mathrm{bar}) \longrightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{g}, 0.01 \mathrm{bar})$

Classify each of the following reactions as one of the four possible types summarized in Table $19.3 :$ (i) spontanous at all temperatures; (ii) not spontaneous at any temperature; (iii) spontaneous at low $T$ but not spontaneous at high $T ;$ (iv) spontaneous at high T but not spontaneous at low $T .$

$$

\begin{array}{c}{\text { (a) } \mathrm{N}_{2}(g)+3 \mathrm{F}_{2}(g) \longrightarrow 2 \mathrm{NF}_{3}(g)} \\ {\Delta H^{\circ}=-249 \mathrm{kJ} ; \Delta S^{\circ}=-278 \mathrm{J} / \mathrm{K}}\\{\text { (b) } \mathrm{N}_{2}(g)+3 \mathrm{Cl}_{2}(g) \longrightarrow 2 \mathrm{NCl}_{3}(g)} \\ {\Delta H^{\circ}=460 \mathrm{kJ} ; \Delta S^{\circ}=-275 \mathrm{J} / \mathrm{K}} \\ {\text { (c) } \mathrm{N}_{2} \mathrm{F}_{4}(g) \longrightarrow 2 \mathrm{NF}_{2}(g)} \\ {\Delta H^{\circ}=85 \mathrm{kJ} ; \Delta S^{\circ}=198 \mathrm{J} / \mathrm{K}}\end{array}

$$

In which of the following systems is entropy increasing? (Do not include the surroundings as part of the system.)

a. An egg is broken and scrambled.

b. A cluttered room is cleaned and organized.

c. A thin stick is placed in a glass of sugar-saturated water, and sugar crystals form on the stick.

(a) Can endothermic chemical reactions be spontaneous?

(b) Can a process be spontaneous at one temperature and nonspontaneous at a different temperature? (c) Water can be decomposed to form hydrogen and oxygen, and the hydrogen and oxygen can be recombined to form water. Does this mean that the processes are thermodynamically reversible? (d) Does the amount of work that a system can do on its surroundings depend on the path of the process?

What single criterion allows us to determine whether a process is spontaneous?

a. The sign of the equilibrium constant, $K$

b. The sign of the enthalpy change, $\Delta H$

c. The sign of the free-energy change, $\Delta G$

d. The sign of the entropy change, $\Delta S$

(II) If 0.45 $\mathrm{kg}$ of water at $100^{\circ} \mathrm{C}$ is changed by a reversible

process to steam at $100^{\circ} \mathrm{C}$ , determine the change in entropy

of $(a)$ the water, $(b)$ the surroundings, and $(c)$ the universe

as a whole. (d) How would your answers differ if the process

were irreversible?

Consider the decomposition of gaseous $\mathrm{N}_{2} \mathrm{O}_{4}$:

$$\mathrm{N}_{2} \mathrm{O}_{4}(g) \longrightarrow 2 \mathrm{NO}_{2}(g) \quad \Delta H^{\circ}=+55.3 \mathrm{kJ} ; \Delta S^{\circ}=+175.7 \mathrm{J} / \mathrm{K}$$

(a) Is this reaction spontaneous under standard-state conditions at $25^{\circ} \mathrm{C} ?$

(b) Estimate the temperature at which the reaction becomes spontaneous.

What are the signs of $\Delta H, \Delta S,$ and $\Delta G$ for the following spontaneous change? Explain.

Given the values of $\Delta H$ and $\Delta S,$ which of the following changes will be spontaneous at constant $T$ and $P ?$

a. $\Delta H=+25 \mathrm{kJ}, \Delta S=+5.0 \mathrm{J} / \mathrm{K}, T=300 . \mathrm{K}$

b. $\Delta H=+25 \mathrm{kJ}, \Delta S=+100 . \mathrm{J} / \mathrm{K}, T=300 . \mathrm{K}$

c. $\Delta H=-10 . \mathrm{kJ}, \Delta S=+5.0 \mathrm{J} / \mathrm{K}, T=298 \mathrm{K}$

d. $\Delta H=-10 . \mathrm{kJ}, \Delta S=-40 . \mathrm{J} / \mathrm{K}, T=200 . \mathrm{K}$

Briefly describe each of the following ideas, phenomena, or methods: (a) the method of initial rates;

(b) activated complex; (c) reaction mechanism;

(d) heterogeneous catalysis; (e) rate-determining step.

Which of these processes result in an entropy decrease of the system?

a. Diluting hydrochloric acid with water

b. Boiling water

c. $2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{NO}_{2}(g)$

d. Making ice cubes in the freezer

What particle is produced in each of the following decay reactions?

a) $^{188}_{80} \mathrm{Hg} \rightarrow^{188}_{79} \mathrm{Au}+?$

b) $^{218} _{85}\mathrm{At} \rightarrow^{214}_{83}\mathrm{Bi}$

c) $_{78}^{170} \mathrm{Pt} \rightarrow^{166}_{76} \mathrm{Os}+?$

Predict the sign of the entropy change in the system for each of the following processes:

(a) A solid sublimes $\quad$ (b) A liquid freezes

(c) $\mathrm{Ag}$ precipitates from a solution containing $\mathrm{Ag}^{+}$ and $\mathrm{I}^{-}$ ions

(d) Gaseous $\mathrm{CO}_{2}$ bubbles out of a carbonated beverage

What type of change, physical or chemical, takes place in each of the following?

a. Water vapor condenses to form rain.

b. Cesium metal reacts explosively with water.

c. Gold melts at $1064^{\circ} \mathrm{C}$

d. A puzzle is cut into 1000 pieces.

e. Cheese is grated.

Is the Haber process for the industrial synthesis of ammonia spontaneous or nonspontaneous under standard conditions at $25^{\circ} \mathrm{C} ?$ At what temperature ( $^{\circ} \mathrm{C} )$

does the changeover occur?

$$

\mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \longrightarrow 2 \mathrm{NH}_{3}(g) \quad \Delta H^{\circ}=-92.2 \mathrm{kJ} ; \Delta S^{\circ}=-199 \mathrm{J} / \mathrm{K}

$$

(II) Which of the following reactions and decays are possible? For those forbidden, explain what laws are violated.

(a) $\pi^{-}+\mathrm{p} \rightarrow \mathrm{n}+\eta^{0}$

(b) $\pi^{+}+\mathrm{p} \rightarrow \mathrm{n}+\pi^{0}$

(c) $\pi^{+}+\mathrm{p} \rightarrow \mathrm{p}+\mathrm{e}^{+}$

(d) $\mathrm{p} \rightarrow \mathrm{e}^{+}+\nu_{\mathrm{c}}$

(d) $\mathrm{p} \rightarrow \mathrm{e}^{+}+\nu_{\mathrm{c}}$

(e) $\mu^{+} \rightarrow \mathrm{e}^{+}+\nu_{\mathrm{c}}$

(f) $\mathrm{p} \rightarrow \mathrm{n}+\mathrm{e}^{+}+\nu_{\mathrm{e}}$

Find the temperatures at which reactions with the following $\Delta H$ and $\Delta S$ values would become spontaneous: (a) $\Delta H=-126 \mathrm{kJ} / \mathrm{mol}, \Delta S=84$ $\mathrm{J} / \mathrm{K} \cdot \mathrm{mol} ;$ (b) $\Delta H=-11.7 \mathrm{kJ} / \mathrm{mol}, \Delta S=-105$ $\mathrm{J} / \mathrm{K} \cdot \mathrm{mol}$.

Tell whether the entropy changes, $\Delta S,$ for the following processes are likely to be positive or negative:

(a) The conversion of liquid water to water vapor at $100^{\circ} \mathrm{C}$

(b) The freezing of liquid water to ice at $0^{\circ} \mathrm{C}$

(c) The eroding of a mountain by a glacier

State whether the entropy of the system increases or decreases in each of the following processes:

(a) Gasoline burns in a car engine.

(b) Gold is extracted and purified from its ore.

(c) Ethanol $\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\right)$ dissolves in 1 -propanol

$\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\right)$

Under what conditions is an endothermic chemical

reaction in which the entropy of the system increases

likely to be spontaneous?

(a) A 5.0-kg rock at a temperature of $20^{\circ} \mathrm{C}$ is dropped into a shallow lake also at $20^{\circ} \mathrm{C}$ from a height of $1.0 \times 10^{3} \mathrm{m} .$ What is the resulting change in entropy of the universe? (b) If the temperature of the rock is $100^{\circ} \mathrm{C}$ when it is dropped, what is the change of entropy of the universe? Assume that air friction is negligible (not a good assumption) and that $c=860 \mathrm{J} / \mathrm{kg} \cdot \mathrm{K}$ is the specific heat of the rock.

An endergonic reaction has the following properties

a. $\quad+\Delta G$ and the reaction is spontaneous.

b. $\quad+\Delta G$ and the reaction is not spontaneous.

c. $\quad-\Delta G$ and the reaction is spontaneous.

d. $\quad-\Delta G$ and the reaction is not spontaneous.

Are the following processes exothermic or endothermic?

a. the combustion of gasoline in a car engine

b. water condensing on a cold pipe

c. $\mathrm{CO}_{2}(s) \rightarrow \mathrm{CO}_{2}(g)$

d. $\mathrm{F}_{2}(g) \rightarrow 2 \mathrm{F}(g)$

Study Figure 8.8

a. How has the cratering rate changed over time? Has it fallen off gradually or abruptly?

b. At present, what is the cratering rate compared to that about 4 billion years ago?

c. Explain why this falloff in cratering rate fits nicely in the theory of planet formation.

Which of the following phenomena is most likely due to the high cohesiveness of water? a) Lakes and rivers freeze from the top down, not the bottom up.

b) The fishing spider can walk across the surface of liquid water.

c) Adding salt to snow makes it melt.

d) The temperature of Santa Monica Bay, off the coast of Los Angeles, fluctuates less than the air temperature throughout the year.

e) All of the above are due to the cohesiveness of water.

Impacts on the terrestrial planets and the Moon

a. are more common than they used to be.

b. have occurred at approximately the same rate since the Solar System formed.

c. are less common than they used to be.

d. periodically become more common and then less common.

e. never occur anymore.

Which of the following is not currently a major cause of species extinctions?

a. Habitat destruction

b. Meteorite impacts

c. Overexploitation

d. Introductions of non-native predators

e. Introductions of non-native pathogens

What is a spontaneous reaction?

What is a spontaneous reaction?

Study Figure 8.10

a. How has the cratering rate changed over time? Has it fallen off gradually or abruptly?

b. At present, what is the cratering rate compared to about 4 billion years ago?

c. Explain why this falloff in cratering rate fits nicely in the theory of planet formation.

(1) What is the change in entropy of 250 $\mathrm{g}$ of steam at $100^{\circ} \mathrm{C}$ when it is condensed to water at $100^{\circ} \mathrm{C}$ ?

(II) Which of the following reactions and decays are possible? For those forbidden, explain what laws are violated.

(a) $\pi^{-}+\mathrm{p} \rightarrow \mathrm{n}+\eta^{0}$

(b) $\pi^{+}+\mathrm{p} \rightarrow \mathrm{n}+\pi^{0}$

(c) $\pi^{+}+\mathrm{p} \rightarrow \mathrm{p}+\mathrm{e}^{+}$

(d) $\mathrm{p} \rightarrow \mathrm{e}^{+}+\nu_{\mathrm{c}}$

$(e) \mu^{+} \rightarrow \mathrm{e}^{+}+\overline{v}_{\mu}$

(f) $\mathrm{p} \rightarrow \mathrm{n}+\mathrm{e}^{+}+\nu_{\mathrm{e}}$

(a) Which reaction is spontaneous in the hydrogen fuel cell: hydrogen gas plus oxygen gas makes water, or water makes hydrogen gas plus oxygen gas? (b) Using the standard reduction potentials in Appendix E, calculate the standard voltage generated by the hydrogen fuel cell in acidic solution.

Impacts on the terrestrial planets and the Moon

a. are more common than they used to be.

b. have occurred at approximately the same rate since the Solar System formed.

c. are less common than they used to be.

d. periodically become more common and then are less common for a while.

e. never occur anymore.

Distinguish between the terms spontaneous and instantaneous. Give an example of a process that is spontaneous but very slow, and one that is very fast but not spontaneous.