Problem 1

What is dependent on the average kinetic

energy of the atoms in a substance?

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Problem 8

How can you tell which one of two samples

will release energy in the form of heat when

the two samples are in contact?

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Problem 15

Which thermodynamic property of a food

is of interest to nutritionists? Why?

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Problem 18

Explain how a comprehensive table of

standard Gibbs energies of formation can

be used to determine the spontaneity

of any chemical reaction.

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Problem 19

What information is needed to be certain

that a chemical reaction is nonspontaneous?

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Problem 20

You need 70.2 $\mathrm{J}$ to raise the temperature of

34.0 $\mathrm{g}$ of ammonia, $\mathrm{NH}_{3}(g),$ from $23.0^{\circ} \mathrm{C}$ to

$24.0^{\circ} \mathrm{C}$ . Calculate the molar heat capacity

of ammonia.

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Problem 21

Calculate $C$ for indium metal given that

1.0 mol In absorbs 53 J during the following

process.

$$\operatorname{In}(s, 297.5 \mathrm{K}) \longrightarrow \operatorname{In}(s, 299.5 \mathrm{K})$$

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Problem 22

Calculate $\Delta H$ when 1.0 mol of nitrogen is

heated from 233 $\mathrm{K}$ to 475 $\mathrm{K}$ .

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Problem 23

What is the change in enthalpy when 11.0 $\mathrm{g}$

of liquid mercury is heated by $15^{\circ} \mathrm{C}$ ?

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Problem 24

Calculate $\Delta H$ when 1.0 $\mathrm{mol}$ of argon is

cooled from 475 $\mathrm{K}$ to 233 $\mathrm{K}$

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Problem 25

What enthalpy change occurs when 112.0 $\mathrm{g}$

of barium chloride experiences a change of

temperature from $15^{\circ} \mathrm{C}$ to $-30^{\circ} \mathrm{C}$ .

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Problem 26

The diagram below represents an interpretation of Hess's law for the following reaction.

$$\mathrm{Sn}(s)+2 \mathrm{Cl}_{2}(g) \rightarrow \mathrm{SnCl}_{4}(l)$$

Use the diagram to determine $\Delta H$ for each

step and the net reaction.

\begin{equation}

\begin{array}{ll}{\mathrm{Sn}(s)+\mathrm{Cl}_{2}(g) \rightarrow \mathrm{SnCl}_{2}(l)} & {\Delta H=?} \\ {\mathrm{SnCl}_{2}(s)+\mathrm{Cl}_{2}(g) \rightarrow \mathrm{SnCl}_{4}(l)} & {\Delta H=?} \\ {\mathrm{Sn}(s)+2 \mathrm{Cl}_{2}(g) \rightarrow \operatorname{SnCl}_{4}(l)} & {\Delta H=?}\end{array}

\end{equation}

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Problem 27

Use tabulated values of standard enthalpies

of formation to calculate the enthalpy

change accompanying the reaction

$4 \mathrm{Al}(s)+6 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 2 \mathrm{Al}_{2} \mathrm{O}_{3}(s)+6 \mathrm{H}_{2}(g)$

Is the reaction exothermic?

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Problem 28

The reaction $2 \mathrm{Fe}_{2} \mathrm{O}_{3}(s)+3 \mathrm{C}(s) \rightarrow 4 \mathrm{Fe}(s)+$

3 $\mathrm{CO}_{2}(g)$ is involved in the smelting of iron.

Use $\Delta H_{f}^{o}$ values to calculate the enthalpy

change during the production of 1 $\mathrm{mol}$

of iron.

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Problem 29

For glucose, $\Delta H_{f}^{o}=-1263 \mathrm{kJ} / \mathrm{mol} .$ Calculate

the enthalpy change when 1 $\mathrm{mol}$ of

$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(s)$ combusts to form $\mathrm{CO}_{2}(g)$ and

$\mathrm{H}_{2} \mathrm{O}(l) .$

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Problem 30

Given the entropy change for the first two

reactions below, calculate the entropy

change for the third reaction below.

\begin{equation}

\begin{array}{c}{\mathrm{S}_{8}(s)+8 \mathrm{O}_{2}(g) \rightarrow 8 \mathrm{SO}_{2}(g) \Delta S=89 \mathrm{J} / \mathrm{K}} \\ {2 \mathrm{SO}_{2}(s)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{SO}_{3}(g) \Delta S=-188 \mathrm{J} / \mathrm{K}} \\ {\mathrm{S}_{8}(s)+12 \mathrm{O}_{2}(g) \rightarrow 8 \mathrm{SO}_{3}(g) \Delta S=?}\end{array}

\end{equation}

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Problem 31

$.$ The standard entropies for the following

substances are 26.9 $\mathrm{J} / \mathrm{K} \bullet$ mol for $\mathrm{MgO}(s)$

213.8 $\mathrm{J} / \mathrm{K} \bullet \mathrm{mol}$ for $\mathrm{CO}_{2}(g),$ and

65.7 $\mathrm{J} / \mathrm{K} \bullet \mathrm{mol}$ for $\mathrm{MgCO}_{3}(s) .$ Determine

the entropy for the reaction below.

$$

\mathrm{MgCO}_{3}(s) \rightarrow \mathrm{MgO}(s)+\mathrm{CO}_{2}(g)

$$

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Problem 32

A reaction has $\Delta H=-356 \mathrm{kJ}$ and $\Delta S=-36$

$\mathrm{J} / \mathrm{K} .$ Calculate $\Delta G$ at $25^{\circ} \mathrm{C}$ to confirm that

the reaction is spontaneous.

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Problem 33

A reaction has $\Delta H=98 \mathrm{kJ}$ and $\Delta S=292 \mathrm{J} / \mathrm{K}$ .

Investigate the spontaneity of the reaction at

room temperature. Would increasing the

temperature have any effect on the

spontaneity of the reaction?

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Problem 34

The sugars glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(a q),$ and

sucrose, $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}(a q),$ have $\Delta G_{f}^{\prime}$ values of

$-915 \mathrm{kJ}$ and $-1551 \mathrm{kJ}$ respectively. Is the

hydrolysis reaction, $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}(a q)+$

$\mathrm{H}_{2} \mathrm{O}(l) \rightarrow 2 \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(a q),$ likely to occur $?$

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Problem 35

How are the coefficients in a chemical

equation used to determine the change in a

thermodynamic property during a chemical

reaction?

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Problem 36

Is the following reaction exothermic? The

standard enthalpy of formation for

$\mathrm{CH}_{2} \mathrm{O}(g)$ is approximately $-109 \mathrm{kJ} / \mathrm{mol}$ .

$$\mathrm{CH}_{2} \mathrm{O}(g)+\mathrm{CO}_{2}(g) \rightarrow \mathrm{H}_{2} \mathrm{O}(g)+2 \mathrm{CO}(g)$$

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Problem 37

Predict whether $\Delta S$ is positive or negative

for the following reaction.

$$\mathrm{Ag}^{+}(a q)+\mathrm{Cl}^{-}(a q) \rightarrow \mathrm{AgCl}(s)$$

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Problem 38

Explain why $\mathrm{AlCl}_{3}$ has a molar heat

capacity that is approximately four times the

molar heat capacity of a metallic crystal.

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Problem 39

At high temperatures, does enthalpy or

entropy have a greater effect on a reaction's

Gibbs energy?

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Problem 40

Calculate the enthalpy of formation for

sulfur dioxide, $\mathrm{SO}_{2},$ from its elements, sulfur

and oxygen. Use the balanced chemical

equation and the following information.

\begin{equation}

\begin{array}{c}{\mathrm{S}(s)+\frac{3}{2} \mathrm{O}_{2}(g) \rightarrow \mathrm{SO}_{3}(g) \quad \Delta H=-395.8 \mathrm{kJ} / \mathrm{mol}} \\ {2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{SO}_{3}(g) \quad \Delta H=-198.2 \mathrm{kJ} / \mathrm{mol}}\end{array}

\end{equation}

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Problem 41

Using the following values, compute the $\Delta G$

value for each reaction and predict whether

they will occur spontaneously.

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Problem 42

Hydrogen gas can be prepared for use in

cars in several ways, such as by the decomposition of water or hydrogen chloride.

$$\begin{array}{l}{2 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g)} \\ {2 \mathrm{HCl}(g) \rightarrow \mathrm{H}_{2}(g)+\mathrm{Cl}_{2}(g)}\end{array}$$

Use the following data to determine whether

these reactions can occur spontaneously at

$25^{\circ} \mathrm{C}$ . Assume that $\Delta H$ and $\Delta S$ are constant.

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Problem 43

Why are the specific heats of $\mathrm{F}_{2}(g)$ and

$\mathrm{Br}_{2}(g)$ very different, whereas their molar

heat capacities are very similar?

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Problem 44

Look at the two pictures below this

question. Which picture appears to have

more order? Why? Are there any

similarities between the order of marbles

and the entropy of particles?

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Problem 45

Why must nutritionists make corrections to

bomb calorimetric data if a food contains

cellulose or other indigestible fibers?

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Problem 46

Give examples of situations in which (a) the

entropy is low; (b) the entropy is high.

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Problem 47

Design an experiment to measure the

molar heat capacities of zinc and copper.

If your teacher approves the design, obtain

the materials needed and conduct the

experiment. When you are finished, com-

pare your experimental values with those

rom a chemical handbook or other

reference source.

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Problem 48

Use the following terms to create a concept

map: calorimeter, enthalpy, entropy, Gibbs

energy, and Hesss's Law

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Problem 49

How would the slope differ if you were to

cool the water at the same rate that graph

shows the water was heated?

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Problem 50

What would a slope of zero indicate about

the temperature of water during heating?

Matthew L.

Numerade Educator

Problem 51

Calculate the slope given the following data.

$$\begin{array}{ll}{y_{2}=3.3 \mathrm{K}} & {x_{2}=50 \mathrm{s}} \\ {y_{1}=5.6 \mathrm{K}} & {x_{1}=30 \mathrm{s}}\end{array}$$

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Problem 52

Calculate the slope given the following data.

$$\begin{array}{ll}{y_{2}=63.7 \mathrm{mL}} & {x_{2}=5 \mathrm{s}} \\ {y_{1}=43.5 \mathrm{mL}} & {x_{1}=2 \mathrm{s}}\end{array}$$

Matthew L.

Numerade Educator

Problem 53

Graphing Calculator

Calculating the Gibbs-Energy Change

The graphing calculator can run a program

that calculates the Gibbs-energy change,

given the temperature, $T$ , change in enthalpy

$\Delta H,$ and change in entropy, $\Delta S .$ Given that

the temperature is 298 $\mathrm{K}$ , the change in

enthalpy is 131.3 $\mathrm{kJ} / \mathrm{mol}$ , and the change in

entropy is $0.134 \mathrm{kJ} /(\mathrm{mol} \cdot \mathrm{K}),$ you can calculate Gibbs-energy change in kilojoules per

mole. Then use the program to make calculations.

Go to Appendix C. If you are using a TI-83

Plus, you can download the program

ENERGY data and run the application

as directed. If you are using another

calculator, your teacher will provide you with

keystrokes and data sets to use. After you

have run the program, answer the following

questions.

\begin{equation}

\begin{array}{l}{\text { a. What is the Gibbs-energy change given a }} \\ {\text { temperature of } 300 \mathrm{K}, \text { a change in enthalpy }} \\ {\text { of } 132 \mathrm{kJ} / \mathrm{mol} \text { and a change in entropy of }} \\ {0.086 \mathrm{kJ} / /(\mathrm{mol} \cdot \mathrm{K}) ?}\\{\text { b. What is the Gibbs-energy change given a }} \\ {\text { temperature of } 288 \mathrm{K}, \text { a change in enthalpy }} \\ {\text { of } 115 \mathrm{kJ} / \mathrm{mol} \text { and a change in entropy of }} \\ {0.113 \mathrm{kJ} /(\mathrm{mol} \cdot \mathrm{K}) ?}\\{\text { c. What is the Gibbs-energy change given a }} \\ {\text { temperature of } 298 \mathrm{K} \text { , a change in enthalpy }} \\ {\text { of } 181 \mathrm{kJ} / \mathrm{mol} \text { and a change in entropy of }} \\ {0.135 \mathrm{kJ} /(\mathrm{mol} \cdot \mathrm{K}) ?}\end{array}

\end{equation}

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