Chemistry The Molecular Nature of Matter

Problem 6

Which thermodynamic quantity corresponds to the heat at constant volume? Which corresponds to the heat at constant pressure?

David Collins

Numerade Educator

01:12

Problem 7

What are the units of $P \Delta V$ if pressure is expressed in pascals and volume is expressed in cubic meters?

David Collins

Numerade Educator

02:10

Problem 8

If there is a decrease in the number of moles of gas during an exothermic chemical reaction, which is numerically larger, $\Delta E$ or $\Delta H ?$ Why?

David Collins

Numerade Educator

01:57

Problem 9

Which of the following changes is accompanied by the most negative value of $\Delta E ?$ (a) A spring is compressed and heated. (b) A compressed spring expands and is cooled.
(c) A spring is compressed and cooled. (d) A compressed spring expands and is heated.

David Collins

Numerade Educator

01:35

Problem 10

What is a spontaneous change? What role does kinetics play in determining the apparent spontaneity of a chemical reaction?

David Collins

Numerade Educator

01:46

Problem 11

List five changes that you have encountered recently that occurred spontaneously. List five changes that are nonspontaneous that you have caused to occur.

David Collins

Numerade Educator

00:20

Problem 12

Which of the items that you listed in Question $19.11$ are exothermic (leading to a lowering of the potential energy) and which are endothermic (accompanied by an increase in potential energy)?

Aadit Sharma

Numerade Educator

01:45

Problem 13

At constant pressure, what role does the enthalpy change play in determining the spontaneity of an event?

David Collins

Numerade Educator

01:49

Problem 14

How do the probabilities of the initial and final states in a process affect the spontaneity of the process?

David Collins

Numerade Educator

01:49

Problem 15

An instant cold pack purchased in a pharmacy contains a packet of solid ammonium nitrate surrounded by a pouch of water. When the packet of $\mathrm{NH}_{4} \mathrm{NO}_{3}$ is broken, the solid dissolves in water and a cooling of the mixture occurs because the solution process for $\mathrm{NH}_{4} \mathrm{NO}_{3}$ in water is endothermic. Explain, in terms of what happens to the molecules and ions, why this mixing occurs spontaneously.

David Collins

Numerade Educator

01:08

Problem 16

What is entropy?

Aadit Sharma

Numerade Educator

01:28

Problem 17

How is the entropy of a substance affected by (a) an increase in temperature, (b) a decrease in volume, (c) changing from a liquid to a solid, and (d) dissociating into individual atoms?

David Collins

Numerade Educator

02:32

Problem 18

Will the entropy change for each of the following be positive or negative?
(a) Moisture condenses on the outside of a cold glass.
(b) Raindrops form in a cloud.
(c) Gasoline vaporizes in the carburetor of an automobile engine.
(d) Air is pumped into a tire.
(e) Frost forms on the windshield of your car.
(f) Sugar dissolves in coffee.

David Collins

Numerade Educator

01:04

Problem 19

On the basis of our definition of entropy, suggest why entropy is a state function.

David Collins

Numerade Educator

01:06

Problem 20

State the second law of thermodynamics.

Amanda Hyde

Numerade Educator

Problem 21

How can a process have a negative entropy change for the system, and yet still be spontaneous?

David Collins

Numerade Educator

Problem 22

What is the third law of thermodynamics?

Aadit Sharma

Numerade Educator

Problem 23

Would you expect the entropy of an alloy (a solution of two metals) to be zero at $0 \mathrm{~K}$ ? Explain your answer.

David Collins

Numerade Educator

01:50

Problem 24

Why does entropy increase with increasing temperature? 19.25 Does glass have $S=0$ at $0 \mathrm{~K}$ ? Explain.

Aadit Sharma

Numerade Educator

Problem 25

Does glass have $S=0$ at $0 \mathrm{~K} ?$ Explain.

David Collins

Numerade Educator

Problem 26

What is the equation expressing the change in the Gibbs free energy for a reaction occurring at constant temperature and pressure?

David Collins

Numerade Educator

01:31

Problem 27

In terms of the algebraic signs of $\Delta H$ and $\Delta S$, under which of the following circumstances will a change be spontaneous:
(a) At all temperatures?
(b) At low temperatures but not at high temperatures?
(c) At high temperatures but not at low temperatures?

David Collins

Numerade Educator

Problem 28

Under what circumstances will a change be nonspontaneous regardless of the temperature?

David Collins

Numerade Educator

02:05

Problem 29

How is free energy related to useful work?

David Collins

Numerade Educator

01:42

Problem 30

What is a thermodynamically reversible process? How is the amount of work obtained from a change related to thermodynamic reversibility?

David Collins

Numerade Educator

01:41

Problem 31

How is the rate at which energy is withdrawn from a system related to the amount of that energy that can appear as useful work?

David Collins

Numerade Educator

01:25

Problem 32

When glucose is oxidized by the body to generate energy, part of the energy is used to make molecules of ATP (adenosine triphosphate). However, of the total energy released in the oxidation of glucose, only $38 \%$ actually goes to making ATP. What happens to the rest of the energy?

David Collins

Numerade Educator

01:49

Problem 33

Why are real, observable changes not considered to be thermodynamically reversible processes?

David Collins

Numerade Educator

Problem 34

In what way is free energy related to equilibrium?

David Collins

Numerade Educator

Problem 35

Considering the fact that the formation of a bond between two atoms is exothermic and is accompanied by an entropy decrease, explain why all chemical compounds decompose into individual atoms if heated to a high enough temperature.

David Collins

Numerade Educator

02:20

Problem 36

When a warm object is placed in contact with a cold one, they both gradually come to the same temperature. On a molecular level, explain how this is related to entropy and spontaneity.

David Collins

Numerade Educator

01:25

Problem 37

Sketch the shape of the free energy curve for a chemical reaction that has a positive $\Delta G^{\circ} .$ Indicate the composition of the reaction mixture corresponding to equilibrium.

David Collins

Numerade Educator

Problem 38

Many reactions that have large, negative values of $\Delta G^{\circ}$ are not actually observed to happen at $25^{\circ} \mathrm{C}$ and 1 atm. Why?

David Collins

Numerade Educator

Problem 39

Suppose a reaction has a negative $\Delta H^{\circ}$ and a negative $\Delta S^{\circ} .$ Will more or less product be present at equilibrium as the temperature is raised?

David Collins

Numerade Educator

Problem 40

Write the equation that relates the free energy change to the value of the reaction quotient for a reaction.

David Collins

Numerade Educator

Problem 41

How is the equilibrium constant related to the standard free energy change for a reaction? (Write the equation.)

David Collins

Numerade Educator

Problem 42

What is the value of $\Delta G^{\circ}$ for a reaction for which $K=1 ?$

David Collins

Numerade Educator

Problem 43

Define the term atomization energy.

David Collins

Numerade Educator

Problem 44

Why are the heats of formation of gaseous atoms from their elements endothermic quantities?

David Collins

Numerade Educator

01:30

Problem 45

The gaseous $\mathrm{C}_{2}$ molecule has a bond energy of $602 \mathrm{~kJ}$ $\mathrm{mol}^{-1}$. Why isn't the standard heat of formation of $\mathrm{C}(\mathrm{g})$ equal to half this value?

David Collins

Numerade Educator

View

Problem 46

A certain system absorbs $0.300 \mathrm{~kJ}$ of heat and has $0.700 \mathrm{~kJ}$ of work performed on it. What is the value of $\Delta E$ for the change? Is the overall change exothermic or endothermic?

Ronald Prasad

Numerade Educator

Problem 47

The value of $\Delta E$ for a certain change is $-1455 \mathrm{~J}$. During the change, the system absorbs $812 \mathrm{~J}$ of heat. Did the system do work, or was work done on the system? How much work, expressed in joules, was involved?

David Collins

Numerade Educator

Problem 48

Suppose that you were pumping an automobile tire with a hand pump that pushed $24.0 \mathrm{in.}^{3}$ of air into the tire on each stroke, and that during one such stroke the opposing pressure in the tire was $30.0 \mathrm{lb} / \mathrm{in} .{ }^{2}$ above the normal atmospheric pressure of $14.7 \mathrm{lb} / \mathrm{in} .^{2}$. Calculate the number of joules of work accomplished during each stroke. $(1 \mathrm{~L} \mathrm{~atm}=101.325 \mathrm{~J})$

David Collins

Numerade Educator

01:39

Problem 49

Consider the reaction between aqueous solutions of baking soda, $\mathrm{NaHCO}_{3}$, and vinegar, $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$.
$\mathrm{NaHCO}_{3}(a q)+\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q) \longrightarrow$
$\mathrm{NaC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{CO}_{2}(g)$
If this reaction occurs at $1.00$ atmospheres of pressure, how much work, expressed in $L$ atm, is done by the system in pushing back the atmosphere when $1.00 \mathrm{~mol} \mathrm{NaHCO}_{3}$ reacts at a temperature of $25^{\circ} \mathrm{C}$ ?

Aadit Sharma

Numerade Educator

16:16

Problem 50

Calculate $\Delta H^{\circ}$ and $\Delta E^{\circ}$ for the following reactions at $25^{\circ} \mathrm{C}$. (If necessary, refer to the data in Table C.2 in Appendix C.)
(a) $3 \mathrm{PbO}(s)+2 \mathrm{NH}_{3}(g) \longrightarrow 3 \mathrm{~Pb}(s)+\mathrm{N}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)$
(b) $\mathrm{NaOH}(s)+\mathrm{HCl}(g) \longrightarrow \mathrm{NaCl}(s)+\mathrm{H}_{2} \mathrm{O}(l)$
(c) $\mathrm{Al}_{2} \mathrm{O}_{3}(s)+2 \mathrm{Fe}(s) \longrightarrow \mathrm{Fe}_{2} \mathrm{O}_{3}(s)+2 \mathrm{Al}(s)$
(d) $2 \mathrm{CH}_{4}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g)+\mathrm{H}_{2}(g)$

Alex M

Numerade Educator

05:28

Problem 51

Calculate $\Delta H^{\circ}$ and $\Delta E^{\circ}$ for the following reactions at $25^{\circ} \mathrm{C}$. (If necessary, refer to the data in Table C.2 in Appendix C.)
(a) $2 \mathrm{C}_{2} \mathrm{H}_{2}(\mathrm{~g})+5 \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow 4 \mathrm{CO}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(g)$
(b) $\mathrm{C}_{2} \mathrm{H}_{2}(g)+5 \mathrm{~N}_{2} \mathrm{O}(g) \longrightarrow$
$2 \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)+5 \mathrm{~N}_{2}(g)$
(c) $\mathrm{NH}_{4} \mathrm{Cl}(s) \longrightarrow \mathrm{NH}_{3}(g)+\mathrm{HCl}(g)$
(d) $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}(l)+4 \mathrm{O}_{2}(g) \longrightarrow 3 \mathrm{CO}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)$

David Collins

Numerade Educator

01:47

Problem 52

The reaction
$$2 \mathrm{~N}_{2} \mathrm{O}(g) \longrightarrow 2 \mathrm{~N}_{2}(g)+\mathrm{O}_{2}(g)$$
has $\Delta H^{\circ}=-163.14 \mathrm{~kJ}$. What is the value of $\Delta E$ for the decomposition of $186 \mathrm{~g}$ of $\mathrm{N}_{2} \mathrm{O}$ at $25^{\circ} \mathrm{C}$ ? If we assume that $\Delta H$ doesn't change appreciably with temperature, what is $\Delta E$ for this same reaction at $217^{\circ} \mathrm{C}$ ?

David Collins

Numerade Educator

04:53

Problem 53

A $10.0 \mathrm{~L}$ vessel at $22^{\circ} \mathrm{C}$ contains butane, $\mathrm{C}_{4} \mathrm{H}_{10}(g)$, at a pressure of $2.00 \mathrm{~atm} .$ What is the maximum amount of work that can be obtained by the combustion of this butane if the gas is first brought to a pressure of $1 \mathrm{~atm}$ and the temperature is brought to $28^{\circ} \mathrm{C}$ ? Assume the products are also returned to this same temperature and pressure.

David Collins

Numerade Educator

01:47

Problem 54

Use the data from Table $7.2$ to calculate $\Delta H^{\circ}$ for the following reactions. On the basis of their values of $\Delta H^{\circ}$, which are favored to occur spontaneously?
(a) $\mathrm{CaO}(s)+\mathrm{CO}_{2}(g) \longrightarrow \mathrm{CaCO}_{3}(s)$
(b) $\mathrm{C}_{2} \mathrm{H}_{2}(\mathrm{~g})+2 \mathrm{H}_{2}(\mathrm{~g}) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g)$
(c) $3 \mathrm{CaO}(s)+2 \mathrm{Fe}(s) \longrightarrow 3 \mathrm{Ca}(s)+\mathrm{Fe}_{2} \mathrm{O}_{3}(s)$

David Collins

Numerade Educator

01:47

Problem 55

Use the data from Table $7.2$ to calculate $\Delta H^{\circ}$ for the following reactions. On the basis of their values of $\Delta H^{\circ}$, which are favored to occur spontaneously?
(a) $\mathrm{NH}_{4} \mathrm{Cl}(s) \longrightarrow \mathrm{NH}_{3}(g)+\mathrm{HCl}(g)$
(b) $2 \mathrm{C}_{2} \mathrm{H}_{2}(g)+5 \mathrm{O}_{2}(g) \longrightarrow 4 \mathrm{CO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(g)$
(c) $\mathrm{C}_{2} \mathrm{H}_{2}(g)+5 \mathrm{~N}_{2} \mathrm{O}(g) \longrightarrow$
$2 \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)+5 \mathrm{~N}_{2}(g)$

David Collins

Numerade Educator

01:25

Problem 56

What factors must you consider to determine the sign of $\Delta S$ for the reaction $2 \mathrm{~N}_{2} \mathrm{O}(g) \longrightarrow 2 \mathrm{~N}_{2}(g)+\mathrm{O}_{2}(g)$ if it
occurs at constant temperature?

David Collins

Numerade Educator

01:24

Problem 57

What factors must you consider to determine the sign of $\Delta S$ for the reaction: $2 \mathrm{HI}(g) \longrightarrow \mathrm{H}_{2}(g)+\mathrm{I}_{2}(s) ?$

David Collins

Numerade Educator

Problem 58

Predict the algebraic sign of the entropy change for the following reactions.
(a) $\mathrm{PCl}_{3}(g)+\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{PCl}_{5}(g)$
(b) $\mathrm{SO}_{2}(g)+\mathrm{CaO}(s) \longrightarrow \mathrm{CaSO}_{3}(s)$
(c) $\mathrm{CO}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{2} \mathrm{CO}_{3}(a q)$
(d) $\mathrm{Ni}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{H}_{2}(g)+\mathrm{NiCl}_{2}(a q)$

David Collins

Numerade Educator

Problem 59

Predict the algebraic sign of the entropy change for the following reactions.
(a) $\mathrm{I}_{2}(s) \longrightarrow \mathrm{I}_{2}(g)$
(b) $\mathrm{Br}_{2}(g)+3 \mathrm{Cl}_{2}(g) \longrightarrow 2 \mathrm{BrCl}_{3}(g)$
(c) $\mathrm{NH}_{3}(g)+\mathrm{HCl}(g) \longrightarrow \mathrm{NH}_{4} \mathrm{Cl}(s)$
(d) $\mathrm{CaO}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{Ca}(\mathrm{OH})_{2}(s)$

David Collins

Numerade Educator

04:10

Problem 60

Calculate $\Delta S^{\circ}$ for the following reactions in $\mathrm{J} \mathrm{K}^{-1}$ from the data in Table 19.1. On the basis of their values of $\Delta S^{\circ}$, which of these reactions are favored to occur spontaneously?
(a) $\mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \longrightarrow 2 \mathrm{NH}_{3}(g)$
(b) $\mathrm{CO}(\mathrm{g})+2 \mathrm{H}_{2}(\mathrm{~g}) \longrightarrow \mathrm{CH}_{3} \mathrm{OH}(l)$
(c) $2 \mathrm{C}_{2} \mathrm{H}_{6}(g)+7 \mathrm{O}_{2}(g) \longrightarrow 4 \mathrm{CO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(g)$
(d) $\mathrm{Ca}(\mathrm{OH})_{2}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(l) \longrightarrow \mathrm{CaSO}_{4}(s)+2 \mathrm{H}_{2} \mathrm{O}(l)$
(e) $\mathrm{S}(s)+2 \mathrm{~N}_{2} \mathrm{O}(g) \longrightarrow \mathrm{SO}_{2}(g)+2 \mathrm{~N}_{2}(g)$

David Collins

Numerade Educator

04:02

Problem 61

Calculate $\Delta S^{\circ}$ for the following reactions in $J \mathrm{~K}^{-1}$, using the data in Table $19.1$.
(a) $\mathrm{Ag}(s)+\frac{1}{2} \mathrm{Cl}_{2}(g) \longrightarrow \mathrm{AgCl}(s)$
(b) $\mathrm{H}_{2}(g)+\frac{1}{2} \mathrm{O}_{2}(g) \longrightarrow \mathrm{H}_{2} \mathrm{O}(g)$
(c) $\mathrm{H}_{2}(g)+\frac{1}{2} \mathrm{O}_{2}(g) \longrightarrow \mathrm{H}_{2} \mathrm{O}(l)$
(d) $\mathrm{CaCO}_{3}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(l) \longrightarrow$
$\mathrm{CaSO}_{4}(s)+\mathrm{H}_{2} \mathrm{O}(g)+\mathrm{CO}_{2}(g)$
(e) $\mathrm{NH}_{3}(g)+\mathrm{HCl}(g) \longrightarrow \mathrm{NH}_{4} \mathrm{Cl}(s)$

David Collins

Numerade Educator

02:16

Problem 62

Calculate $\Delta S_{\mathrm{f}}^{\circ}$ for the following compounds in $\mathrm{J} \mathrm{mol}^{-1} \mathrm{~K}^{-1}$
(a) $\mathrm{C}_{2} \mathrm{H}_{4}(g)$
(c) $\mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}(s)$
(b) $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(l)$

David Collins

Numerade Educator

02:22

Problem 63

Calculate $\Delta S_{f}^{o}$ for the following compounds in $\mathrm{J} \mathrm{mol}^{-1} \mathrm{~K}^{-1}$
(a) $\mathrm{Al}_{2} \mathrm{O}_{3}(s)$
(c) $\mathrm{NH}_{4} \mathrm{Cl}(s)$
(b) $\mathrm{CaSO}_{4} \cdot \frac{1}{2} \mathrm{H}_{2} \mathrm{O}(s)$

David Collins

Numerade Educator

01:07

Problem 64

Nitrogen dioxide, $\mathrm{NO}_{2}$, an air pollutant, dissolves in rainwater to form a dilute solution of nitric acid. The equation for the reaction is
$$3 \mathrm{NO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2 \mathrm{HNO}_{3}(l)+\mathrm{NO}(g)$$
Calculate $\Delta S^{\circ}$ for this reaction in $\mathrm{J} \mathrm{K}^{-1}$.

David Collins

Numerade Educator

00:52

Problem 65

Good wine will turn to vinegar if it is left exposed to air, because the alcohol is oxidized to acetic acid. The equation for the reaction is
$$\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(l)+\mathrm{H}_{2} \mathrm{O}(l)$$
Calculate $\Delta S^{\circ}$ for this reaction in $\mathrm{J} \mathrm{K}^{-1}$.

Aadit Sharma

Numerade Educator

Problem 66

Phosgene, $\mathrm{COCl}_{2}$, was used as a war gas during World War I. It reacts with the moisture in the lungs to produce $\mathrm{HCl}$, which causes the lungs to fill with fluid, and CO, which asphyxiates the victim. Both lead ultimately to death. For $\mathrm{COCl}_{2}(g), S^{\circ}=284 \mathrm{~J} / \mathrm{mol} \mathrm{K}$ and
$\Delta H_{\mathrm{f}}^{\mathrm{o}}=-223 \mathrm{~kJ} / \mathrm{mol}$. Use this information and the
data in Table $19.1$ to calculate $\Delta G_{\mathrm{f}}^{\circ}$ for $\mathrm{COCl}_{2}(g)$ in $\mathrm{kJ} \mathrm{mol}^{-1} .$

David Collins

Numerade Educator

01:40

Problem 67

Aluminum oxidizes rather easily, but forms a thin protective coating of $\mathrm{Al}_{2} \mathrm{O}_{3}$ that prevents further oxidation of the aluminum beneath. Use the data for $\Delta H_{\mathrm{f}}^{\circ}$ (Table 7.2) and $S^{\circ}$ (Table 19.1) to calculate $\Delta G_{\mathrm{f}}^{\circ}$ for $\mathrm{Al}_{2} \mathrm{O}_{3}(s)$ in $\mathrm{kJ} \mathrm{mol}^{-1}$.

David Collins

Numerade Educator

01:29

Problem 68

Compute $\Delta G^{\circ}$ in $\mathrm{kJ}$ for the following reactions, using the data in Table $19.2$.
(a) $\mathrm{SO}_{3}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{2} \mathrm{SO}_{4}(l)$
(b) $2 \mathrm{NH}_{4} \mathrm{Cl}(s)+\mathrm{CaO}(s) \longrightarrow$
$\mathrm{CaCl}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l)+2 \mathrm{NH}_{3}(g)$
(c) $\mathrm{CaSO}_{4}(s)+2 \mathrm{HCl}(g) \longrightarrow \mathrm{CaCl}_{2}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(l)$

David Collins

Numerade Educator

Problem 69

Compute $\Delta G^{\circ}$ in $\mathrm{kJ}$ for the following reactions, using the data in Table $19.2$.
(a) $2 \mathrm{HCl}(\mathrm{g})+\mathrm{CaO}(s) \longrightarrow \mathrm{CaCl}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(g)$
(b) $2 \mathrm{AgCl}(s)+\mathrm{Ca}(s) \longrightarrow \mathrm{CaCl}_{2}(s)+2 \mathrm{Ag}(s)$
(c) $3 \mathrm{NO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2 \mathrm{HNO}_{3}(l)+\mathrm{NO}(g)$

David Collins

Numerade Educator

01:12

Problem 70

Given the following,
$4 \mathrm{NO}(g) \longrightarrow 2 \mathrm{~N}_{2} \mathrm{O}(g)+\mathrm{O}_{2}(g) \quad \Delta G^{\circ}=-139.56 \mathrm{~kJ}$
$2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{NO}_{2}(g) \quad \Delta G^{\circ}=-69.70 \mathrm{~kJ}$
calculate $\Delta G^{\circ}$ for the reaction
$$2 \mathrm{~N}_{2} \mathrm{O}(g)+3 \mathrm{O}_{2}(g) \longrightarrow 4 \mathrm{NO}_{2}(g)$$

Aadit Sharma

Numerade Educator

01:33

Problem 71

Given the following reactions and their $\Delta G^{\circ}$ values,
$\mathrm{COCl}_{2}(g)+4 \mathrm{NH}_{3}(g) \longrightarrow \mathrm{CO}\left(\mathrm{NH}_{2}\right)_{2}(s)+2 \mathrm{NH}_{4} \mathrm{Cl}(s)$
$\Delta G^{\circ}=-332.0 \mathrm{~kJ}$
$\mathrm{COCl}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{CO}_{2}(g)+2 \mathrm{HCl}(g)$
$\Delta G^{\circ}=-141.8 \mathrm{~kJ}$
$\mathrm{NH}_{3}(g)+\mathrm{HCl}(g) \longrightarrow \mathrm{NH}_{4} \mathrm{Cl}(s) \quad \Delta G^{\circ}=-91.96 \mathrm{~kJ}$
Calculate the value of $\Delta G^{\circ}$ for the reaction
$\mathrm{CO}\left(\mathrm{NH}_{2}\right)_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{CO}_{2}(g)+2 \mathrm{NH}_{3}(g)$

David Collins

Numerade Educator

Problem 72

Gasohol is a mixture of gasoline and ethanol (grain alcohol), $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$. Calculate the maximum work that could be obtained at $25^{\circ} \mathrm{C}$ and 1 atm by burning $1 \mathrm{~mol}$ of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$.
$$\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)$$

Aadit Sharma

Numerade Educator

01:33

Problem 73

What is the maximum amount of useful work that could possibly be obtained at $25^{\circ} \mathrm{C}$ and 1 atm from the combustion of $48.0 \mathrm{~g}$ of natural gas, $\mathrm{CH}_{4}(g)$ to give $\mathrm{CO}_{2}(g)$ and $\mathrm{H}_{2} \mathrm{O}(g) ?$

David Collins

Numerade Educator

01:20

Problem 74

Chloroform, formerly used as an anesthetic and now believed to be a carcinogen, has a heat of vaporization $\Delta H_{\text {vaporianion }}=31.4 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The change, $\mathrm{CHCl}_{3}(l)$
$\mathrm{CHCl}_{3}(g)$, has $\Delta S^{\circ}=94.2 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$. At what tempera-
ture do we expect $\mathrm{CHCl}_{3}$ to boil (i.e., at what temperature will liquid and vapor be in equilibrium at 1 atm pressure)?

Aadit Sharma

Numerade Educator

00:50

Problem 75

For the melting of aluminum, $\mathrm{Al}(s) \longrightarrow \mathrm{Al}(l), \Delta H^{\circ}=$
$10.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and $\Delta S^{\circ}=9.50 \mathrm{~J} / \mathrm{mol} \mathrm{K}$. Calculate the
melting point of Al. (The actual melting point is $660^{\circ} \mathrm{C}$.)

Aadit Sharma

Numerade Educator

01:11

Problem 76

Isooctane, an important constituent of gasoline, has a boiling point of $99.3^{\circ} \mathrm{C}$ and a heat of vaporization of $37.7 \mathrm{~kJ} \mathrm{~mol}^{-1}$. What is $\Delta S$ (in $\mathrm{J} \mathrm{mol}^{-1} \mathrm{~K}^{-1}$ ) for the
vaporization of $1 \mathrm{~mol}$ of isooctane?

Aadit Sharma

Numerade Educator

Problem 77

Acetone (nail polish remover) has a boiling point of $56.2^{\circ} \mathrm{C}$. The change, $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}(l) \longrightarrow\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}(g)$
has $\Delta H^{\circ}=31.9 \mathrm{~kJ} \mathrm{~mol}^{-1}$. What is $\Delta S^{\circ}$ for this change?

David Collins

Numerade Educator

01:10

Problem 78

Determine whether the following reaction (equation unbalanced) will be spontaneous at $25^{\circ} \mathrm{C}$. (Do we expect appreciable amounts of products to form?)
$\mathrm{C}_{2} \mathrm{H}_{4}(g)+\mathrm{HNO}_{3}(l) \longrightarrow$
$\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(l)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{NO}(g)+\mathrm{NO}_{2}(g)$

David Collins

Numerade Educator

04:23

Problem 79

Which of the following reactions (equations unbalanced) would be expected to be spontaneous at $25^{\circ} \mathrm{C}$ and 1 atm?
(a) $\mathrm{PbO}(s)+\mathrm{NH}_{3}(g) \longrightarrow \mathrm{Pb}(s)+\mathrm{N}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)$
(b) $\mathrm{NaOH}(s)+\mathrm{HCl}(g) \longrightarrow \mathrm{NaCl}(s)+\mathrm{H}_{2} \mathrm{O}(l)$
(c) $\mathrm{Al}_{2} \mathrm{O}_{3}(s)+\mathrm{Fe}(s) \longrightarrow \mathrm{Fe}_{2} \mathrm{O}_{3}(s)+\mathrm{Al}(s)$
(d) $2 \mathrm{CH}_{4}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g)+\mathrm{H}_{2}(g)$

David Collins

Numerade Educator

02:31

Problem 80

Calculate the value of the thermodynamic equilibrium constant for the following reactions at $25^{\circ} \mathrm{C}$. (Refer to the data in Appendix C.2.)
(a) $2 \mathrm{PCl}_{3}(g)+\mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{POCl}_{3}(g)$
(b) $2 \mathrm{SO}_{3}(g) \rightleftharpoons 2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g)$

David Collins

Numerade Educator

02:03

Problem 81

Calculate the value of the thermodynamic equilibrium constant for the following reactions at $25^{\circ} \mathrm{C}$. (Refer to the data in Appendix C.2.)
(a) $\mathrm{N}_{2} \mathrm{H}_{4}(g)+2 \mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{NO}(g)+2 \mathrm{H}_{2} \mathrm{O}(g)$
(b) $\mathrm{N}_{2} \mathrm{H}_{4}(g)+6 \mathrm{H}_{2} \mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{NO}_{2}(g)+8 \mathrm{H}_{2} \mathrm{O}(g)$

David Collins

Numerade Educator

01:57

Problem 82

The reaction $\mathrm{NO}_{2}(\mathrm{~g})+\mathrm{NO}(\mathrm{g}) \rightleftharpoons \mathrm{N}_{2} \mathrm{O}(\mathrm{g})+\mathrm{O}_{2}(g)$
has $\Delta G_{1273}^{\circ}=-9.67 \mathrm{~kJ} .$ A $1.00 \mathrm{~L}$ reaction vessel at $1000.0{ }^{\circ} \mathrm{C}$ contains $0.0200 \mathrm{~mol} \mathrm{NO}_{2}, 0.040 \mathrm{~mol} \mathrm{NO}$,
$0.015 \mathrm{~mol} \mathrm{~N}_{2} \mathrm{O}$, and $0.0350 \mathrm{~mol} \mathrm{O}_{2}$. Is the reaction at equi-
librium? If not, in which direction will the reaction proceed to reach equilibrium?

Aadit Sharma

Numerade Educator

01:29

Problem 83

The reaction $\mathrm{CO}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightleftharpoons \mathrm{HCHO}_{2}(g)$ has
$\Delta G_{673}^{\circ}=+79.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$. If a mixture at $673 \mathrm{~K}$ contains
$0.040 \mathrm{~mol} \mathrm{CO}, 0.022 \mathrm{~mol} \mathrm{H}_{2} \mathrm{O}$, and $3.8 \times 10^{-3} \mathrm{~mol}$
$\mathrm{HCHO}_{2}$ in a $2.50 \mathrm{~L}$ container, is the reaction at equilibrium? If not, in which direction will the reaction proceed spontaneously?

David Collins

Numerade Educator

Problem 84

A reaction that can convert coal to methane (the chief
component of natural gas) is
$$\mathrm{C}(s)+2 \mathrm{H}_{2}(g) \rightleftharpoons \mathrm{CH}_{4}(g)$$
for which $\Delta G^{\circ}=-50.79 \mathrm{~kJ} \mathrm{~mol}^{-1}$. What is the value of $K_{\mathrm{p}}$ for this reaction at $25^{\circ} \mathrm{C}$ ? Does this value of $K_{\mathrm{p}}$ suggest that studying this reaction as a means of methane production is worthwhile pursuing?

David Collins

Numerade Educator

01:07

Problem 85

One of the important reactions in living cells from which the organism draws energy is the reaction of adenosine triphosphate (ATP) with water to give adenosine diphosphate (ADP) and free phosphate ion.
$$\mathrm{ATP}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{ADP}+\mathrm{PO}_{4}^{3-}$$
The value of $\Delta G_{310}^{\circ}$ for this reaction at $37^{\circ} \mathrm{C}$ (normal human body temperature) is $-33 \mathrm{~kJ} \mathrm{~mol}^{-1} .$ Calculate the value of the equilibrium constant for the reaction at this temperature.

David Collins

Numerade Educator

01:10

Problem 86

What is the value of the equilibrium constant for a reaction for which $\Delta G^{\circ}=0$ ? What will happen to the composition of the system if we begin the reaction with the pure products?

David Collins

Numerade Educator

00:52

Problem 87

Methanol, a potential replacement for gasoline as an automotive fuel, can be made from $\mathrm{H}_{2}$ and $\mathrm{CO}$ by the reaction
$$\mathrm{CO}(g)+2 \mathrm{H}_{2}(g) \rightleftharpoons \mathrm{CH}_{3} \mathrm{OH}(g)$$
At $500.0 \mathrm{~K}$, this reaction has $K_{\mathrm{p}}=6.25 \times 10^{-3} .$ Calculate $\Delta G_{500}^{o}$ for this reaction in units of kilojoules.

Aadit Sharma

Numerade Educator

00:43

Problem 88

Use the data in Table $19.4$ to compute the approximate atomization energy of $\mathrm{NH}_{3}$.

Aadit Sharma

Numerade Educator

01:04

Problem 89

Approximately how much energy would be released during the formation of the bonds in one mole of acetone molecules? Acetone, the solvent usually found in nail polish remover, has the structural formula

David Collins

Numerade Educator

02:55

Problem 90

The standard heat of formation of ethanol vapor, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{g})$, is $-235.3 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Use the data in Table
$19.3$ and the average bond energies for $\mathrm{C}-\mathrm{C}, \mathrm{C}-\mathrm{H}$, and $\mathrm{O}-\mathrm{H}$ bonds to estimate the $\mathrm{C}-\mathrm{O}$ bond energy in this molecule. The structure of the molecule is

David Collins

Numerade Educator

01:38

Problem 91

The standard heat of formation of ethylene, $\mathrm{C}_{2} \mathrm{H}_{4}(g)$, is $+52.284 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Calculate the $\mathrm{C}=\mathrm{C}$ bond energy in this molecule.

David Collins

Numerade Educator

01:28

Problem 92

Carbon disulfide, $\mathrm{CS}_{2}$, has the Lewis structure $: \ddot{S}=\mathrm{C}=\ddot{\mathrm{S}}^{*}$, and for $\mathrm{CS}_{2}(g), \Delta H_{\mathrm{f}}^{\circ}=+115.3 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Use the data in Table $19.3$ to calculate the average $\mathrm{C}=\mathrm{S}$ bond energy in this molecule.

David Collins

Numerade Educator

01:32

Problem 93

Gaseous hydrogen sulfide, $\mathrm{H}_{2} \mathrm{~S}$, has $\Delta H_{\mathrm{f}}^{\circ}=-20.15 \mathrm{~kJ}$
$\mathrm{mol}^{-1}$. Use the data in Table $19.3$ to calculate the average $\mathrm{S}-\mathrm{H}$ bond energy in this molecule.

David Collins

Numerade Educator

01:11

Problem 94

For $\mathrm{SF}_{6}(g), \Delta H_{\mathrm{f}}^{\mathrm{o}}=-1096 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Use the data in
Table $19.3$ to calculate the average $S-\mathrm{F}$ bond energy in $\mathrm{SF}_{6}$

David Collins

Numerade Educator

Problem 95

Use the results of the preceding problem and the data in Table C.3 of Appendix $C$ to calculate the standard heat of formation of $\mathrm{SF}_{4}(g)$. The measured value of $\Delta H_{\mathrm{f}}^{\circ}$ for $\mathrm{SF}_{4}(g)$ is $-718.4 \mathrm{~kJ} \mathrm{~mol}^{-1}$. What is the percentage difference between your calculated value of $\Delta H_{\mathrm{f}}^{\circ}$ and the experimentally determined value?

David Collins

Numerade Educator

01:08

Problem 96

Use the data in Tables $19.3$ and $19.4$ to estimate the standard heat of formation of acetylene, $\mathrm{H}-\mathrm{C} \equiv \mathrm{C}-\mathrm{H}$, in the gaseous state.

David Collins

Numerade Educator

Problem 97

What would be the approximate heat of formation of $\mathrm{CCl}_{4}$ vapor at $25^{\circ} \mathrm{C}$ and $1 \mathrm{~atm} ?$

David Collins

Numerade Educator

01:44

Problem 98

Which substance should have the more exothermic heat of formation, $\mathrm{CF}_{4}$ or $\mathrm{CCl}$ ?

David Collins

Numerade Educator

01:57

Problem 99

Would you expect the value of $\Delta H_{\mathrm{f}}^{\circ}$ for benzene, $\mathrm{C}_{6} \mathrm{H}_{6}$ computed from tabulated bond energies, to be very close to the experimentally measured value of $\Delta H_{1}^{\text {?? }}$ Justify your answer.

David Collins

Numerade Educator

Problem 100

If pressure is expressed in atmospheres and volume is expressed in liters, $P \Delta V$ has units of $L$ atm (liters $x$ atmospheres). In Chapter 11 you learned that 1 atm $=$ $101,325 \mathrm{~Pa}$, and in Chapter 2 you learned that $1 \mathrm{~L}=$ $1 \mathrm{dm}^{3}$. Use this information to determine the number of joules corresponding to $1 \mathrm{~L}$ atm.

Aadit Sharma

Numerade Educator

01:04

Problem 101

Calculate the work, in joules, done by a gas as it expands at constant temperature from a volume of $3.00 \mathrm{~L}$ and $a$ pressure of $5.00 \mathrm{~atm}$ to a volume of $8.00 \mathrm{~L} .$ The external pressure against which the gas expands is $1.00 \mathrm{~atm}$. $(1 \mathrm{~atm}=101,325 \mathrm{~Pa})$.

David Collins

Numerade Educator

01:06

Problem 102

When an ideal gas expands at a constant temperature, $\Delta E=0$ for the change. Why?

David Collins

Numerade Educator

Problem 103

When a real gas expands at a constant temperature, $\Delta E>0$ for the change. Why?

David Collins

Numerade Educator

01:15

Problem 104

An ideal gas in a cylinder fitted with a piston expands at constant temperature from a pressure of $5 \mathrm{~atm}$ and $a$ volume of $6.0 \mathrm{~L}$ to a final volume of $12 \mathrm{~L}$ against a constant opposing pressure of $2.5 \mathrm{~atm} .$ How much heat does the gas absorb, expressed in units of $\mathrm{L}$ atm (liter $\times$ atm)? (Hint: See Exercise 19.102.)

David Collins

Numerade Educator

01:10

Problem 105

A cylinder fitted with a piston contains $5.00 \mathrm{~L}$ of a gas at a pressure of $4.00 \mathrm{~atm} .$ The entire apparatus is contained in a water bath to maintain a constant temperature of $25^{\circ} \mathrm{C}$. The piston is released and the gas expands until the pressure inside the cylinder equals the atmospheric pressure outside, which is 1 atm. Assume ideal gas behavior and calculate the amount of work done by the gas as it expands at constant temperature.

David Collins

Numerade Educator

05:46

Problem 106

The experiment described in Exercise $19.105$ is repeated, but this time a weight, which exerts a pressure of $2 \mathrm{~atm}$, is placed on the piston. When the gas expands, its pressure drops to this 2 atm pressure. Then the weight is removed and the gas is allowed to expand again to a final pressure of 1 atm. Throughout both expansions the temperature of the apparatus was held at a constant $25^{\circ} \mathrm{C}$. Calculate the amount of work performed by the gas in each step. How does the combined total amount of work in this two-step expansion compare with the amount of work done by the gas in the one-step expansion described in Exercise $19.105 ?$ How can even more work be obtained by the expansion of the gas?

Ronald Prasad

Numerade Educator

01:08

Problem 107

When potassium iodide dissolves in water, the mixture becomes cool. For this change, which is of a larger magnitude, $T \Delta S$ or $\Delta H ?$

David Collins

Numerade Educator

03:57

Problem 108

The enthalpy of combustion, $\Delta H_{\text {combustion }}^{\circ}$ of oxalic acid, $\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(s)$, is $-246.05 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Consider the
following data:
(a) Write the balanced thermochemical equation that describes the combustion of one mole of oxalic acid.
(b) Write the balanced thermochemical equation that describes the formation of one mole of oxalic acid.
(c) Use the information in the table above and the equations in parts (a) and (b) to calculate $\Delta H_{\mathrm{t}}^{\circ}$ for oxalic acid.
(d) Calculate $\Delta S_{\mathrm{f}}^{\circ}$ for oxalic acid and $\Delta S^{\circ}$ for the combustion of one mole of oxalic acid.
(e) Calculate $\Delta G_{\mathrm{f}}^{\mathrm{o}}$ for oxalic acid and $\Delta G^{\circ}$ for the combustion of one mole of oxalic acid.

Adriano Chikande

Numerade Educator

00:52

Problem 109

Many biochemical reactions have positive values for $\Delta G^{\circ}$ and seemingly should not be expected to be spontaneous. They occur, however, because they are chemically coupled with other reactions that have negative values of $\Delta G^{\circ}$. An example is the set of reactions that forms the beginning part of the sequence of reactions involved in the metabolism of glucose, a sugar. Given these reactions and their corresponding $\Delta G^{\circ}$ values, glucose $+$ phosphate $\longrightarrow$ glucose 6 -phosphate $+\mathrm{H}_{2} \mathrm{O}$
$\Delta G^{\circ}=+13.13 \mathrm{~kJ}$
$\mathrm{ATP}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{ADP}+$ phosphate
$\Delta G^{\circ}=-32.22 \mathrm{~kJ}$
calculate $\Delta G^{\circ}$ for the coupled reaction
glucose + ATP $\longrightarrow$ glucose 6-phosphate $+$ ADP

Aadit Sharma

Numerade Educator

01:01

Problem 110

The reaction $$2 \mathrm{C}_{4} \mathrm{H}_{10}(g)+13 \mathrm{O}_{2}(g) \longrightarrow 8 \mathrm{CO}_{2}(g)+10 \mathrm{H}_{2} \mathrm{O}(g)$$
has $\Delta G^{\circ}=-5407 \mathrm{~kJ}$. Determine the value of $\Delta G_{i}^{\circ}$ for $\mathrm{C}_{4} \mathrm{H}_{10}(g) .$ Calculate the value of $K_{c}$ for the reaction at $25^{\circ} \mathrm{C} .$

Aadit Sharma

Numerade Educator

04:57

Problem 111

At $1500^{\circ} \mathrm{C}, K_{c}=5.67$ for the reaction
$$\mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightleftharpoons \mathrm{CO}(g)+3 \mathrm{H}_{2}(g)$$
Calculate the value of $\Delta G_{1773}^{\circ}$ for the reaction at this
temperature.

David Collins

Numerade Educator

00:25

Problem 112

Given the following reactions and their values of $\Delta G^{\circ}$, calculate the value of $\Delta G_{\mathrm{f}}^{\circ}$ for $\mathrm{N}_{2} \mathrm{O}_{5}(g)$
$2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(l) \quad \Delta G^{\circ}=-474.4 \mathrm{~kJ}$
$\mathrm{N}_{2} \mathrm{O}_{5}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2 \mathrm{HNO}_{3}(l)$
$\Delta G^{\circ}=-37.6 \mathrm{~kJ}$
$\frac{1}{2} \mathrm{~N}_{2}(g)+\frac{1}{2} \mathrm{O}_{2}(g)+\frac{1}{2} \mathrm{H}_{2}(g) \longrightarrow \mathrm{HNO}_{3}(l)$
$\Delta G^{\circ}=-79.91 \mathrm{~kJ}$

Aadit Sharma

Numerade Educator

00:34

Problem 113

At room temperature $\left(25^{\circ} \mathrm{C}\right)$, the gas CINO is impure because it decomposes slightly according to the equation
$$2 \mathrm{CINO}(g) \rightleftharpoons \mathrm{Cl}_{2}(g)+2 \mathrm{NO}(g)$$
The extent of decomposition is about $5 \%$. What is the approximate value of $\Delta G_{298}^{o}$ for this reaction at this temperature?

Aadit Sharma

Numerade Educator

02:21

Problem 114

The reaction
$$\mathrm{N}_{2} \mathrm{O}(g)+\mathrm{O}_{2}(g) \rightleftharpoons \mathrm{NO}_{2}(g)+\mathrm{NO}(g)$$
has $\Delta H^{\circ}=-42.9 \mathrm{~kJ}$ and $\Delta S^{\circ}=-26.1 \mathrm{~J} / \mathrm{K}$. Suppose
$0.100 \mathrm{~mol}$ of $\mathrm{N}_{2} \mathrm{O}$ and $0.100 \mathrm{~mol}$ of $\mathrm{O}_{2}$ are placed in a
$2.00 \mathrm{~L}$ container at $475^{\circ} \mathrm{C}$ and this equilibrium is established. What percentage of the $\mathrm{N}_{2} \mathrm{O}$ has reacted? (Note: Assume that $\Delta H$ and $\Delta S$ are relatively insensitive to temperature, so $\Delta H_{298}^{\circ}$ and $\Delta S_{29 \mathrm{~s}}^{\circ}$ are about the same as $\Delta H_{773}^{\circ}$ and $\Delta S_{773}^{\circ}$, respectively.)

Alexander Clippinger

Numerade Educator

00:18

Problem 115

Use the data in Table $19.3$ to calculate the bond energy in the nitrogen molecule and the oxygen molecule.

Aadit Sharma

Numerade Educator

02:15

Problem 116

The heat of vaporization of carbon tetrachloride, $\mathrm{CCl}_{4}$, is $29.9 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Using this information and data in Tables $19.3$ and $19.4$, estimate the standard heat of formation of liquid $\mathrm{CCl}_{d}$.

Oluwapelumi Kolawole

Numerade Educator

Problem 117

At $25^{\circ} \mathrm{C}, 0.0560 \mathrm{~mol} \mathrm{O}_{2}$ and $0.020 \mathrm{~mol} \mathrm{~N}_{2} \mathrm{O}$ were
placed in a $1.00 \mathrm{~L}$ container where the following equilibrium was then established.
$$2 \mathrm{~N}_{2} \mathrm{O}(g)+3 \mathrm{O}_{2}(g) \rightleftharpoons 4 \mathrm{NO}_{2}(g)$$
At equilibrium, the $\mathrm{NO}_{2}$ concentration was $0.020 \mathrm{M}$. Calculate the value of $\Delta G^{\circ}$ for the reaction.

David Collins

Numerade Educator

01:11

Problem 118

For the substance $\mathrm{SO}_{2} \mathrm{~F}_{2}(g), \Delta H_{\mathrm{f}}^{\circ}=-858 \mathrm{~kJ} \mathrm{~mol}^{-1}$.
The structure of the $\mathrm{SO}_{2} \mathrm{~F}_{2}$ molecule is Use the value of the $S-F$ bond energy calculated in Problem $19.94$ and the data in Appendix $\mathrm{C} .3$ to determine the average $S=\mathrm{O}$ bond energy in $\mathrm{SO}_{2} \mathrm{~F}_{2}$ in units of $\mathrm{kJ} \mathrm{mol}^{-1}$.

David Collins

Numerade Educator

20:49

Problem 119

Ethyl alcohol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$, has been suggested as an alternative to gasoline as a fuel. In Example $19.5$ we calculated $\Delta G^{\circ}$ for combustion of $1 \mathrm{~mol}$ of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$; in Example $19.6$ we calculated $\Delta G^{\circ}$ for combustion of 1 mol of octane. Let's assume that gasoline has the same properties as octane (one of its constituents). The density of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$ is $0.7893 \mathrm{~g} / \mathrm{mL} ;$ the density of
octane, $\mathrm{C}_{8} \mathrm{H}_{18}$, is $0.7025 \mathrm{~g} / \mathrm{mL}$. Calculate the maximum work that could be obtained by burning 1 gallon ( $3.78$ liters) each of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$ and $\mathrm{C}_{8} \mathrm{H}_{18} .$ On a volume basis, which is the better fuel?

Tianyu Li

Numerade Educator

01:15

Problem 120

When solutions of sodium hydroxide are used to neutralize hydrochloric acid, the standard heat of reaction is found to be $-55.86 \mathrm{~kJ}$. When propionic acid $\mathrm{HC}_{3} \mathrm{H}_{5} \mathrm{O}_{2}$ is neutralized with sodium hydroxide the standard heat of the reaction is $-49.23 \mathrm{~kJ} .$ What is the standard heat and entropy change for the ionization of propionic acid?

Aadit Sharma

Numerade Educator

02:24

Problem 121

You've recently inherited a fortune and immediately after that an inventor approaches you with the investment deal of a lifetime. The inventor has found a "system" to react water with methane to make methanol and hydrogen gas, two potentially valuable fuels. In your interview with the inventor, it is claimed that a revolutionary new catalyst shifts the equilibrium position of the reaction to favor products and that $134 \mathrm{~kg}$ of methanol are produced for each 117 cubic meters of methane used (at STP). Use your knowledge of chemical principles to find all of the flaws in this project before deciding to risk your new fortune on it.

David Collins

Numerade Educator

01:15

Problem 122

A certain weak acid has a $\mathrm{p} K_{\mathrm{a}}$ of $5.83$. When $100.0 \mathrm{~mL}$ of a $0.00525 M$ solution of this weak acid at $21.26^{\circ} \mathrm{C}$ is reacted with $45.6 \mathrm{~mL}$ of $0.00634 M$ sodium hydroxide $\left(\mathrm{HA}+\mathrm{OH}^{-} \longrightarrow \mathrm{A}^{-}+\mathrm{H}_{2} \mathrm{O}\right)$ at $22.18^{\circ} \mathrm{C}$, the tem-
perature of the mixture rises to $24.88^{\circ} \mathrm{C}$. What is the entropy change associated with the ionization $\left(\mathrm{HA} \longrightarrow \mathrm{A}^{-}+\mathrm{H}^{+}\right)$ of this weak acid? (Assume that
the volumes are additive and the densities of the two solutions are $1.000 \mathrm{~g} \mathrm{~cm}^{-3}$, with a specific heat that is the same as pure water.)

Aadit Sharma

Numerade Educator

04:42

Problem 123

On earth, we do not normally find collections of individual subatomic particles, such as protons, neutrons, and electrons. Rather, they are assembled into atoms of various kinds. On the other hand, in the interior of stars individual atoms don't exist. There, an atom would break apart into separate subatomic particles. Explain this in terms of the principles of thermodynamics.

Nadir Iqbal

Numerade Educator