Chemistry

Kenneth W Whitten

Chapter 13

Liquids and Solids - all with Video Answers

Educators

Chapter Questions

Problem 1

What causes dispersion forces? What factors determine the strengths of dispersion forces between molecules?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 2

What is hydrogen bonding? Under what conditions can hydrogen bonds be formed?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 3

Which of the following substances have permanent dipole-dipole forces? (a) $\mathrm{GeH}_{4} ;$ (b) molecular $\mathrm{MgCl}_{2}$;
(c) $\mathrm{PI}_{3} ;(\mathrm{d}) \mathrm{F}_{2} \mathrm{O}$.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 4

Which of the following substances have permanent dipole-dipole forces? (a) molecular $\mathrm{AlBr}_{3} ;$ (b) $\mathrm{PCl}_{5} ;$ (c) NO;
(d) $\mathrm{SeF}_{4}$.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 5

For which of the substances in Exercise 3 are dispersion forces the only important forces in determining boiling points?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 6

For which of the substances in Exercise 4 are dispersion forces the only important forces in determining boiling points?

Crystal Wang

Numerade Educator

Problem 7

For each of the following pairs of compounds, predict which compound would exhibit stronger hydrogen bonding. Justify your prediction. It may help to write a Lewis formula for each. (a) water, $\mathrm{H}_{2} \mathrm{O}$, or hydrogen sulfide, $\mathrm{H}_{2} \mathrm{~S}$;
(b) dichloromethane, $\mathrm{CH}_{2} \mathrm{Cl}_{2}$ or fluoroamine, $\mathrm{NH}_{2} \mathrm{~F} ;$
(c) acetone, $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$ (contains a $\mathrm{C}=\mathrm{O}$ double bond) or ethanol, $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ (contains one $\mathrm{C}-\mathrm{O}$ single bond).

Lottie Adams

Numerade Educator

Problem 8

Which of the following substances exhibits strong hydrogen bonding in the liquid and solid states? (a) $\mathrm{CH}_{3} \mathrm{OH}$ (methanol); (b) $\mathrm{PH}_{3}$; (c) $\mathrm{CH}_{4}$; (d) $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH} ;$ (e) $\mathrm{CH}_{3} \mathrm{NH}_{2}$.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 9

Describe the intermolecular forces that are present in each of the following compounds. Which kind of force would have the greatest influence on the properties of each compound? (a) bromine pentafluoride, $\mathrm{BrF}_{5} ;$ (b) acetone, $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$ (contains a central $\mathrm{C}=\mathrm{O}$ double bond); $(\mathrm{c})$ formaldehyde, $\mathrm{H}_{2} \mathrm{CO}$.

Lottie Adams

Numerade Educator

Problem 10

Describe the intermolecular forces that are present in each of the following compounds. Which kind of force would have the greatest influence on the properties of each compound? (a) ethyl alcohol, $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ (contains one $\mathrm{C}-\mathrm{O}$ single bond); (b) phosphine, $\mathrm{PH}_{3} ;$ (c) sulfur hexafluoride, $\mathrm{SF}_{6}$.

Crystal Wang

Numerade Educator

Problem 11

Account for the fact that ethylene glycol $\left(\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}\right)$ is less viscous than glycerine $\left(\mathrm{HOCH}_{2} \mathrm{CHOHCH}_{2} \mathrm{OH}\right)$, but more viscous than ethyl alcohol $\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\right)$.

Lottie Adams

Numerade Educator

Problem 12

Hydrogen bonding is a very strong dipole-dipole interaction. Why is hydrogen bonding so strong in comparison with other dipole-dipole interactions?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 13

Which of the following substances exhibits strong hydrogen bonding in the liquid and solid states? (a) $\mathrm{H}_{2} \mathrm{~S}$;
(b) $\mathrm{NH}_{3} ;$ (c) $\mathrm{SiH}_{4}$;
(d) HF;
(e) HCl.

Lottie Adams

Numerade Educator

Problem 14

Q The molecular weights of $\mathrm{SiH}_{4}$ and $\mathrm{PH}_{3}$ are nearly the same. Account for the fact that the melting and boiling points of $\mathrm{PH}_{3}\left(-133^{\circ} \mathrm{C}\right.$ and $\left.-88^{\circ} \mathrm{C}\right)$ are higher than those of $\mathrm{SiH}_{4}\left(-185^{\circ} \mathrm{C}\right.$ and $\left.-112^{\circ} \mathrm{C}\right)$.

Crystal Wang

Numerade Educator

Problem 15

Give an example of each of the six types of phase changes.

Crystal Wang

Numerade Educator

Problem 16

For each of the following pairs of compounds, predict which would exhibit hydrogen bonding. Justify your prediction. It may help to write a Lewis formula for each. (a) ammonia, $\mathrm{NH}_{3}$, or phosphine, $\mathrm{PH}_{3} ;$ (b) ethylene, $\mathrm{C}_{2} \mathrm{H}_{4}$, or hydrazine, $\mathrm{N}_{2} \mathrm{H}_{4} ;$ (c) hydrogen fluoride, HF, or hydrogen chloride, HCl.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 17

A Imagine replacing one $\mathrm{H}$ atom of a methane molecule, $\mathrm{CH}_{4}$, with another atom or group of atoms. Account for the order in the normal boiling points of the resulting compounds: $\mathrm{CH}_{4}\left(-161^{\circ} \mathrm{C}\right) ; \mathrm{CH}_{3} \operatorname{Br}\left(3.59^{\circ} \mathrm{C}\right) ; \mathrm{CH}_{3} \mathrm{~F}$
$\left(-78^{\circ} \mathrm{C}\right) ; \mathrm{CH}_{3} \mathrm{OH}\left(65^{\circ} \mathrm{C}\right)$

Lottie Adams

Numerade Educator

Problem 18

Water forms a concave meniscus in a 10-mL glass graduated cylinder but the meniscus it forms in a $10-\mathrm{mL}$ plastic graduated cylinder is flat. Why is the appearance of the water surface in these two measuring devices different?

Crystal Wang

Numerade Educator

Problem 19

Why does HF have a lower boiling point and lower heat of vaporization than $\mathrm{H}_{2} \mathrm{O}$, even though their molecular weights are nearly the same and the hydrogen bonds between molecules of $\mathrm{HF}$ are stronger?

Lottie Adams

Numerade Educator

Problem 20

Many carboxylic acids form dimers in which two molecules "stick together." These dimers result from the formation of two hydrogen bonds between the two molecules. Use acetic acid to draw a likely structure for this kind of hydrogen-bonded dimer.

Crystal Wang

Numerade Educator

Problem 21

Use the kinetic-molecular theory to describe the behavior of liquids with changing temperature. Why are liquids denser than gases?

Lottie Adams

Numerade Educator

Problem 22

Within each group, assign each of the boiling points to the appropriate substance on the basis of intermolecular forces. (a) Ne, Ar, Kr: $-246^{\circ} \mathrm{C},-186^{\circ} \mathrm{C},-152{ }^{\circ} \mathrm{C} ;$ (b) $\mathrm{NH}_{3}$, $\mathrm{H}_{2} \mathrm{O}, \mathrm{HF}:-33^{\circ} \mathrm{C}, 20^{\circ} \mathrm{C}, 100^{\circ} \mathrm{C}$.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 23

Support or criticize the statement that liquids with high normal boiling points have low vapor pressures. Give examples of three common liquids that have relatively high vapor pressures at $25^{\circ} \mathrm{C}$ and three that have low vapor pressures at $25^{\circ} \mathrm{C}$.

Crystal Wang

Numerade Educator

Problem 24

(a) What is the definition of the normal boiling point?
(b) Why is it necessary to specify the atmospheric pressure over a liquid when measuring a boiling point?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 25

Within each group, assign each of the boiling points to the respective substances on the basis of intermolecular forces. (a) $\mathrm{N}_{2}, \mathrm{HCN}, \mathrm{C}_{2} \mathrm{H}_{6}:-196^{\circ} \mathrm{C},-89^{\circ} \mathrm{C}, 26^{\circ} \mathrm{C} ;(\mathrm{b}) \mathrm{H}_{2}$, $\mathrm{HCl}, \mathrm{Cl}_{2}:-35^{\circ} \mathrm{C},-259^{\circ} \mathrm{C},-85^{\circ} \mathrm{C}$.

Lottie Adams

Numerade Educator

Problem 26

Distinguish between evaporation and boiling. Use the kinetic-molecular theory to explain the dependence of rate of evaporation on temperature.

Crystal Wang

Numerade Educator

Problem 27

What factors determine how viscous a liquid is? How does viscosity change with increasing temperature?

Lottie Adams

Numerade Educator

Problem 28

What is the surface tension of a liquid? What causes this property? How does surface tension change with increasing temperature?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 29

Dispersion forces are extremely weak in comparison to the other intermolecular attractions. Explain why this is so.

Lottie Adams

Numerade Educator

Problem 30

What are some of the similarities of the molecular-level descriptions of the viscosity, surface tension, vapor pressure, and rate of evaporation of a liquid?

Crystal Wang

Numerade Educator

Problem 31

What happens inside a capillary tube when a liquid "wets" the tube? What happens when a liquid does not. "wet" the tube?

Lottie Adams

Numerade Educator

Problem 32

Choose from each pair the substance that, in the liquid state, would have the greater vapor pressure at a given temperature. Base your choice on predicted strengths of intermolecular forces. (a) $\mathrm{BiBr}_{3}$ or $\mathrm{BiCl}_{3} ;$ (b) $\mathrm{CO}$ or $\mathrm{CO}_{2}$;
(c) $\mathrm{N}_{2}$ or $\mathrm{NO}$;
(d) $\mathrm{CH}_{3} \mathrm{COOH}$ or $\mathrm{HCOOCH}_{3}$.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 33

Q Repeat Exercise 32 for (a) $\mathrm{C}_{2} \mathrm{H}_{6}$ or $\mathrm{C}_{2} \mathrm{Cl}_{6} ;$ (b) $\mathrm{F}_{2} \mathrm{C}=\mathrm{O}$ or $\mathrm{CH}_{3} \mathrm{OH} ;$ (c) $\mathrm{He}$ or $\mathrm{H}_{2}$

Crystal Wang

Numerade Educator

Problem 34

Q. The temperatures at which the vapor pressures of the following liquids are all 100 torr are given. Predict the order of increasing boiling points of the liquids: butane, $\mathrm{C}_{4} \mathrm{H}_{10}$ $-44.2^{\circ} \mathrm{C} ; 1$ -butanol, $\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}, 70.1^{\circ} \mathrm{C} ;$ diethyl ether. $\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O},-11.5^{\circ} \mathrm{C}$

Crystal Wang

Numerade Educator

Problem 35

Plot a vapor pressure curve for $\mathrm{GaCl}_{3}$ from the following vapor pressures. Determine the boiling point of $\mathrm{GaCl}_{3}$ under a pressure of 250 torr from the plot:
$$
\begin{array}{llrrllll}
t\left({ }^{\circ} \mathrm{C}\right) & 91 & 108 & 118 & 132 & 153 & 176 & 200 \\
\operatorname{vp} \text { (torr) } & 20 . & 40 . & 60 . & 100 . & 200 . & 400 . & 760 .
\end{array}
$$

Lottie Adams

Numerade Educator

Problem 36

Plot a vapor pressure curve for $\mathrm{GaCl}_{3}$ from the following vapor pressures. Determine the boiling point of $\mathrm{GaCl}_{3}$ under a pressure of 250 torr from the plot:
\begin{array}{lcrrrrrrr}
t\left({ }^{\circ} \mathrm{C}\right) & -24 & -13 & -2 & 10 & 29 & 45 & 62 & 79 \\
\text { vp (torr) } & 5.0 & 10 . & 20 . & 40 . & 100 . & 200 . & 400 . & 760 .
\end{array}

Crystal Wang

Numerade Educator

Problem 37

The vapor pressure of liquid bromine at room temperature is 168 torr. Suppose that bromine is introduced drop by drop into a closed system containing air at 775 torr and room temperature. (The volume of liquid bromine is negligible compared to the gas volume.) If the bromine is added until no more vaporizes and a few drops of liquid are present in the flask, what would be the total pressure? What would be the total pressure if the volume of this closed system were decreased to one half its original value at the same temperature?

Lottie Adams

Numerade Educator

Problem 38

A closed flask contains water at $75.0^{\circ} \mathrm{C}$. The total pressure of the air-and-water-vapor mixture is $633.5$ torr. The vapor pressure of water at this temperature is given in Appendix $\mathrm{E}$ as $289.1$ torr. What is the partial pressure of the air in the flask?

Crystal Wang

Numerade Educator

Problem 39

A closed flask contains water at $75.0^{\circ} \mathrm{C}$. The total pressure of the air-and-water-vapor mixture is $633.5$ torr. The vapor pressure of water at this temperature is given in Appendix E as $289.1$ torr. What is the partial pressure of the air in the flask?

Crystal Wang

Numerade Educator

Problem 40

A The heat of vaporization of water at $100^{\circ} \mathrm{C}$ is $2.26 \mathrm{~kJ} / \mathrm{g} ; \mathrm{at}$ $37^{\circ} \mathrm{C}$ (body temperature), it is $2.41 \mathrm{~kJ} / \mathrm{g}$. (a) Convert the latter value to standard molar heat of vaporization, $\Delta H_{\text {vap }}^{\circ}$, at \begin{array}{l}
37^{\circ} \mathrm{C} \text { . (b) Why is the heat of vaporization greater at } 37^{\circ} \mathrm{C}\\
\text { than at } 100^{\circ} \mathrm{C} \text { ? }
\end{array}

Crystal Wang

Numerade Educator

Problem 41

Plot a vapor pressure curve for $\mathrm{C}_{2} \mathrm{Cl}_{2} \mathrm{~F}_{4}$ from the following vapor pressures. Determine the boiling point of $\mathrm{C}_{2} \mathrm{Cl}_{2} \mathrm{~F}_{4}$ under a pressure of 300 . torr from the plot:
$\begin{array}{lllllll}{ }\left({ }^{\circ} \mathrm{C}\right) & -95.4 & -72.3 & -53.7 & -39.1 & -12.0 & 3.5\end{array}$
$\begin{array}{lll}\text { (torr) } & 1.0 & 10 .\end{array}$
$\begin{array}{llll}40 . & 100 . & 400 . & 760 .\end{array}$

Crystal Wang

Numerade Educator

Problem 42

Plot a vapor pressure curve for $\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{~F}_{2}$ from the following vapor pressures. From the plot, determine the boiling point of $\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{~F}_{2}$ under a pressure of 200 . torr.
$\left({ }^{\circ} \mathrm{C}\right)$ $\begin{array}{llll}-77.2 & -51.2 & -31.1 & -15.0\end{array}$ $\begin{array}{rr}14.8 & 31.7\end{array}$
P (torr) $1.0$ $\begin{array}{lllll}10 . & 40 . & 100 . & 400 . & 760 .\end{array}$ $\mathrm{rD}$

Crystal Wang

Numerade Educator

Problem 43

What amount of heat energy, in joules, must be removed to condense $24.4 \mathrm{~g}$ of water vapor at $123.5^{\circ} \mathrm{C}$ to liquid at $23.0^{\circ} \mathrm{C} ?$

Crystal Wang

Numerade Educator

Problem 44

Is the equilibrium that is established between two physical states of matter an example of static or dynamic equilibrium? How could one demonstrate the type of equilibrium established? Explain your answer.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 45

Which of the following changes of state are exothermic? Explain. (a) fusion; (b) liquefaction; (c) sublimation; (d) deposition.

Lottie Adams

Numerade Educator

Problem 46

Suppose that heat was added to a $21.8-g$ sample of solid zinc at the rate of $9.84 \mathrm{~J} / \mathrm{s}$. After the temperature reached the normal melting point of zinc, $420 .{ }^{\circ} \mathrm{C}$, it remained constant for $3.60$ minutes. Calculate $\Delta H_{\text {fusion }}^{\circ}$ at $420 .{ }^{\circ} \mathrm{C}$, in $\mathrm{J} / \mathrm{mol}$, for zinc.

Crystal Wang

Numerade Educator

Problem 47

The specific heat of silver is $0.237 \mathrm{~J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}$. Its melting point is $961^{\circ} \mathrm{C}$. Its heat of fusion is $11 \mathrm{~J} / \mathrm{g}$. How much heat is needed to change $9.72 \mathrm{~g}$ of silver from solid at $24^{\circ} \mathrm{C}$ to liquid at $961^{\circ} \mathrm{C}^{2}$

Crystal Wang

Numerade Educator

Problem 48

The heat of fusion of thallium is $21 \mathrm{~J} / \mathrm{g}$, and its heat of vaporization is $795 \mathrm{~J} / \mathrm{g}$. The melting and boiling points are $304^{\circ} \mathrm{C}$ and $1457^{\circ} \mathrm{C}$. The specific heat of liquid thallium is $0.13 \mathrm{~J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}$. How much heat is needed to change $204 \mathrm{~g}$ of solid thallium at $304^{\circ} \mathrm{C}$ to vapor at $1457^{\circ} \mathrm{C}$ and 1 atm?

Crystal Wang

Numerade Educator

Problem 49

Calculate the amount of heat required to convert $70.0 \mathrm{~g}$ of ice at $0^{\circ} \mathrm{C}$ to liquid water at $100 .{ }^{\circ} \mathrm{C}$.

Crystal Wang

Numerade Educator

Problem 50

Calculate the amount of heat required to convert $70.0 \mathrm{~g}$ of ice at $-15.0^{\circ} \mathrm{C}$ to steam at $125.0^{\circ} \mathrm{C}$.

Crystal Wang

Numerade Educator

Problem 51

Use data in Appendix $\mathrm{E}$ to calculate the amount of heat required to warm $170 . \mathrm{g}$ of mercury from $25^{\circ} \mathrm{C}$ to its boiling point and then to vaporize it.

Crystal Wang

Numerade Educator

Problem 52

If $275 \mathrm{~g}$ of liquid water at $100 .{ }^{\circ} \mathrm{C}$ and $550 \mathrm{~g}$ of water at $30.0^{\circ} \mathrm{C}$ are mixed in an insulated container, what is the final temperature?

Crystal Wang

Numerade Educator

Problem 53

If $20.0 \mathrm{~g}$ of ice at $-10.0^{\circ} \mathrm{C}$ and $20.0 \mathrm{~g}$ of liquid water at $100 .{ }^{\circ} \mathrm{C}$ are mixed in an insulated container, what will the final temperature be?

John Nicolle

Numerade Educator

Problem 54

If $180 . \mathrm{g}$ of liquid water at $0^{\circ} \mathrm{C}$ and $18.0 \mathrm{~g}$ of steam at $110 .{ }^{\circ} \mathrm{C}$ are mixed in an insulated container, what will the final temperature be?

Crystal Wang

Numerade Educator

Problem 55

Water can be cooled in hot climates by the evaporation of water from the surfaces of canvas bags. What mass of water can be cooled from $35.0^{\circ} \mathrm{C}$ to $30.0^{\circ} \mathrm{C}$ by the evaporation of one gram of water? Assume that $\Delta H_{\mathrm{vap}}$ does not change with temperature.

Crystal Wang

Numerade Educator

Problem 56

(a) How much heat must be removed to prepare $14.0 \mathrm{~g}$ of ice at $0.0^{\circ} \mathrm{C}$ from $14.0 \mathrm{~g}$ of water at $25.0^{\circ} \mathrm{C} ?$ (b) Calculate the mass of water at $100.0^{\circ} \mathrm{C}$ that could be cooled to $23.5^{\circ} \mathrm{C}$ by the same amount of heat as that calculated in part (a).

Lottie Adams

Numerade Educator

Problem 57

Toluene, $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{3}$, is a liquid used in the manufacture of TNT. Its normal boiling point is $111.0^{\circ} \mathrm{C}$, and its molar heat of vaporization is $35.9 \mathrm{~kJ} / \mathrm{mol}$. What would be the vapor pressure (torr) of toluene at $75.00^{\circ} \mathrm{C}$ ?

Crystal Wang

Numerade Educator

Problem 58

At their normal boiling points, the heat of vaporization of water $\left(100^{\circ} \mathrm{C}\right)$ is $40,656 \mathrm{~J} / \mathrm{mol}$ and that of heavy water $\left(101.41^{\circ} \mathrm{C}\right)$ is $41,606 \mathrm{~J} / \mathrm{mol}$. Use these data to calculate the vapor pressure of each liquid at $80.00^{\circ} \mathrm{C}$.

Lottie Adams

Numerade Educator

Problem 59

(a) Use the Clausius-Clapeyron equation to calculate the temperature $\left({ }^{\circ} \mathrm{C}\right)$ at which pure water would boil at a pressure of $400.0$ torr. (b) Compare this result with the temperature read from Figure $13-13 .$ (c) Compare the results of
(a) and (b) with a value obtained from Appendix E.

Lottie Adams

Numerade Educator

Problem 60

Show that the Clausius-Clapeyron equation can be written as
$$
P=\frac{-\Delta H_{\mathrm{vap}}}{R T}+B
$$
where $B$ is a constant that has different values for different substances. This is an equation for a straight line. (a) What is the expression for the slope of this line? (b) Using the following vapor pressure data, plot $\ln P$ vs. $1 / T$ for ethyl acetate, $\mathrm{CH}_{3} \mathrm{COOC}_{2} \mathrm{H}_{5}$, a common organic solvent used in nail polish removers. $\begin{array}{lccccc}t\left({ }^{\circ} \mathrm{C}\right) & -43.4 & -23.5 & -13.5 & -3.0 & +9.1 \\ \operatorname{vp} \text { (torr) } & 1 & 5 & 10 . & 20 . & 40 . \\ t\left({ }^{\circ} \mathrm{C}\right) & 16.6 & 27.0 & 42.0 & 59.3 & \\ \operatorname{vp} \text { (torr) } & 60 . & 100 . & 200 . & 400 . & \end{array}$
(c) From the plot, estimate $\Delta H_{\mathrm{vap}}$ for ethyl acetate.
(d) From the plot, estimate the normal boiling point of ethyl acetate.

Crystal Wang

Numerade Educator

Problem 61

A Repeat Exercise $60(\mathrm{~b})$ and $60(\mathrm{c})$ for mercury, using the following data for liquid mercury. Then compare this value with the one in Appendix $\mathrm{E}$.
$\begin{array}{lcccll}t\left({ }^{\circ} \mathrm{C}\right) & 126.2 & 184.0 & 228.8 & 261.7 & 323.0 \\ \text { vp (torr) } & 1 & 10 . & 40 . & 100 . & 400 .\end{array}$

Crystal Wang

Numerade Educator

Problem 62

Isopropyl alcohol, $\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}$, is marketed as "rubbing alcohol." Its vapor pressure is 100 . torr at $39.5^{\circ} \mathrm{C}$ and 400 . torr at $67.8^{\circ} \mathrm{C}$. Estimate the molar heat of vaporization of isopropyl alcohol.

Lottie Adams

Numerade Educator

Problem 63

Using data from Exercise 62 , predict the normal boiling point of isopropyl alcohol.

Lottie Adams

Numerade Educator

Problem 64

Boiling mercury is often used in diffusion pumps to attain a very high vacuum; pressures down to $10^{-10}$ atm can be readily attained with such a system. Mercury vapor is very toxic to inhale, however. The normal boiling point of liquid mercury is $357^{\circ} \mathrm{C}$. What would be the vapor pressure of mercury at $25^{\circ} \mathrm{C}$ ?

Lottie Adams

Numerade Educator

Problem 65

How many phases exist at a triple point? Describe what would happen if a small amount of heat were added under constant-volume conditions to a sample of water at the triple point. Assume a negligible volume change during fusion.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 66

What is the critical point? Will a substance always be a liquid below the critical temperature? Why or why not?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 67

Refer to the phase diagram of $\mathrm{CO}_{2}$ in Active Figure $13-17 \mathrm{~b}$ to answer Exercises $67-70$.
What phase of $\mathrm{CO}_{2}$ exists at $1.25$ atm pressure and a temperature of (a) $-90^{\circ} \mathrm{C}$, (b) $-60^{\circ} \mathrm{C}$, (c) $0^{\circ} \mathrm{C}$ ?

Crystal Wang

Numerade Educator

Problem 68

What phases of $\mathrm{CO}_{2}$ are present (a) at a temperature of $-78^{\circ} \mathrm{C}$ and a pressure of $1.0 \mathrm{~atm}$ ? (b) at $-57^{\circ} \mathrm{C}$ and a pressure of $5.2$ atm?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 69

List the phases that would be observed if a sample of $\mathrm{CO}_{2} \mathrm{at}$ 10 atm pressure were heated from $-80^{\circ} \mathrm{C}$ to $40^{\circ} \mathrm{C}$.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 70

How does the melting point of $\mathrm{CO}_{2}$ change with pressure? What does this indicate about the relative density of solid $\mathrm{CO}_{2}$ versus liquid $\mathrm{CO}_{2} ?$

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 71

A You are given the following data for ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$.
Normal melting point $-117^{\circ} \mathrm{C}$
Normal boiling point $78.0^{\circ} \mathrm{C}$
Critical temperature $243^{\circ} \mathrm{C}$
Critical pressure $63.0 \mathrm{~atm}$
Assume that the triple point is slightly lower in temperature than the melting point and that the vapor pressure at the triple point is about $10^{-5}$ torr. (a) Sketch a phase diagram for ethanol. (b) Ethanol at 1 atm and $140 .{ }^{\circ} \mathrm{C}$ is compressed to $70 .$ atm. Are two phases present at any time during this process? (c) Ethanol at 1 atm and $270 .{ }^{\circ} \mathrm{C}$ is compressed to 70 . atm. Are two phases present at any time during this process?

Crystal Wang

Numerade Educator

Problem 72

( You are given the following data for butane, $\mathrm{C}_{4} \mathrm{H}_{10}$
Normal melting point $-138^{\circ} \mathrm{C}$
Normal boiling point $0^{\circ} \mathrm{C}$
Critical temperature $152^{\circ} \mathrm{C}$
Critical pressure 38 atm
Assume that the triple point is slightly lower in temperature than the melting point and that the vapor pressure at the triple point is $3 \times 10^{-5}$ torr. (a) Sketch a phase diagram for butane. (b) Butane at 1 atm and $140^{\circ} \mathrm{C}$ is compressed to $40 \mathrm{~atm}$. Are two phases present at any time during this process? (c) Butane at 1 atm and $200^{\circ} \mathrm{C}$ is compressed to 40 atm. Are two phases present at any time during this process?

Crystal Wang

Numerade Educator

Problem 73

Refer to the phase diagram for sulfur. (The vertical axis is on a logarithmic scale.) Sulfur has two solid forms, monoclinic and rhombic.
- (a) How many triple points are there for sulfur?
(b) Indicate the approximate pressure and temperature at each triple point. (c) Which phases are in equilibrium at each triple point?

Lottie Adams

Numerade Educator

Problem 74

Refer to the phase diagram for sulfur. (The vertical axis is on a logarithmic scale.) Sulfur has two solid forms, monoclinic and rhombic.
Which physical states should be present at equilibrium under the following conditions? (a) $10^{-1}$ atm and $110^{\circ} \mathrm{C}$;
(b) $10^{-5}$ atm and $80^{\circ} \mathrm{C}$;
(c) $5 \times 103 \mathrm{~atm}$ and $160^{\circ} \mathrm{C}$;
(d) $10^{-1}$ atm and $80^{\circ} \mathrm{C}$;
(e) $10^{-5}$ atm and $140^{\circ} \mathrm{C}$; (f) 1 atm and $140^{\circ} \mathrm{C} .$

Crystal Wang

Numerade Educator

Problem 75

I Comment on the following statement: "The only perfectly ordered state of matter is the crystalline state."

Crystal Wang

Numerade Educator

Problem 76

Ice floats in water. Why? Would you expect solid mercury to float in liquid mercury at its freezing point? Explain.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 77

Distinguish among and compare the characteristics of molecular, covalent, ionic, and metallic solids. Give two examples of each kind of solid.

Lottie Adams

Numerade Educator

Problem 78

Classify each of the following substances, in the solid state, as molecular, ionic, covalent (network), or metallic solids:

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 79

Q Classify each of the following substances, in the solid state, as molecular, ionic, covalent (network), or metallic solids:

Crystal Wang

Numerade Educator

Problem 80

Based only on their formulas, classify each of the following in the solid state as a molecular, ionic, covalent (network), or metallic solid: (a) $\mathrm{SO}_{2} \mathrm{~F}$, (b) $\mathrm{MgF}_{2}$, (c) $\mathrm{W}$, (d) $\mathrm{Pb},(\mathrm{e}) \mathrm{PF}_{5}$

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 81

Based only on their formulas, classify each of the following in the solid state as a molecular, ionic, covalent (network), or metallic solid: (a) $\mathrm{Au}$, (b) $\mathrm{NO}_{2}$, (c) $\mathrm{CaF}_{2},(\mathrm{~d}) \mathrm{SF}_{4}$, (e) $\mathrm{C}_{\text {diamond }}$.

Lottie Adams

Numerade Educator

Problem 82

Arrange the following solids in order of increasing melting points and account for the order: $\mathrm{NaF}, \mathrm{MgF}_{2}$, AlF $_{3}$.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 83

Q Arrange the following solids in order of increasing melting points and account for the order: $\mathrm{MgO}, \mathrm{CaO}, \mathrm{SrO}$, $\mathrm{BaO} .$

Crystal Wang

Numerade Educator

Problem 84

Distinguish among and sketch simple cubic, body-centered cubic (bcc), and face-centered cubic (fcc) lattices. Use $\mathrm{CsCl}$, sodium, and nickel as examples of solids existing in simple cubic, bcc, and fcc lattices, respectively.

Crystal Wang

Numerade Educator

Problem 85

Describe a unit cell as precisely as you can.

Lottie Adams

Numerade Educator

Problem 86

Determine the number of ions of each type present in each unit cell shown in Figure $13-29$.

Lottie Adams

Numerade Educator

Problem 87

Refer to Figure $13-29$ a. (a) If the unit cell edge is represented as $a$, what is the distance (center to center) from $\mathrm{Cs}^{+}$ to its nearest neighbor? (b) How many equidistant nearest neighbors does each $\mathrm{Cs}^{+}$ ion have? What are the identities of these nearest neighbors? (c) What is the distance (center to center), in terms of $a$, from a $\mathrm{Cs}^{+}$ ion to the nearest $\mathrm{Cs}^{+}$ ion? (d) How many equidistant nearest neighbors does each $\mathrm{Cl}^{-}$ ion have? What are their identities?

Lottie Adams

Numerade Educator

Problem 88

Refer to Figure $13-28$. (a) If the unit cell edge is represented as $a$, what is the distance (center to center) from $\mathrm{Na}^{+}$ to its nearest neighbor? (b) How many equidistant nearest neighbors does each $\mathrm{Na}^{+}$ ion have? What are the identities of these nearest neighbors? (c) What is the distance (center to center), in terms of $a$, from a $\mathrm{Na}^{+}$ ion to the nearest $\mathrm{Na}^{+}$ ion? (d) How many equidistant nearest neighbors does each $\mathrm{Cl}^{-}$ ion have? What are their identities?

Crystal Wang

Numerade Educator

Problem 89

Polonium crystallizes in a simple cubic unit cell with an edge length of $3.36$ ?. (a) What is the mass of the unit cell? (b) What is the volume of the unit cell? (c) What is the theoretical density of Po?

Crystal Wang

Numerade Educator

Problem 90

Calculate the density of Na metal. The length of the bodycentered cubic unit cell is $4.24 \AA$.

Crystal Wang

Numerade Educator

Problem 92

The atomic radius of iridium is $1.36 \AA$ A. The unit cell of iridium is a face-centered cube. Calculate the density of iridium.

Crystal Wang

Numerade Educator

Problem 93

A certain metal has a specific gravity of $10.200$ at $25^{\circ} \mathrm{C}$. It crystallizes in a body-centered cubic arrangement with a unit cell edge length of $3.147 \AA$. Determine the atomic weight, and identify the metal.

Crystal Wang

Numerade Educator

Problem 94

The structure of diamond follows, with each sphere representing a carbon atom. (a) How many carbon atoms are there per unit cell in the diamond structure? (b) Verify, by extending the drawing if necessary, that each carbon atom has four nearest neighbors. What is the arrangement of these nearest neighbors? (c) What is the distance (center to center) from any carbon atom to its nearest neighbor, expressed in terms of $a$, the unit cell edge? (d) The observed unit cell edge length in diamond is $3.567 \AA$. What is the $\mathrm{C}-\mathrm{C}$ single bond length in diamond? (e) Calculate the density of diamond.

Crystal Wang

Numerade Educator

Problem 95

The crystal structure of $\mathrm{CO}_{2}$ is cubic, with a cell edge length of $5.540$ A. A diagram of the cell is shown in Figure $13-31$ a. (a) What is the number of molecules of $\mathrm{CO}_{2}$ per unit cell? (b) Is this structure face-centered cubic? How can you tell? (c) What is the density of solid $\mathrm{CO}_{2}$ at this temperature?

Crystal Wang

Numerade Educator

Problem 96

A Group 4A element with a density of $11.35 \mathrm{~g} / \mathrm{cm}^{3}$ crystallizes in a face-centered cubic lattice whose unit cell edge length is $4.95 \AA$. Calculate its atomic weight. What is the element?

Lottie Adams

Numerade Educator

Problem 97

Crystalline silicon has the same structure as diamond, with a unit cell edge length of $5.430 \AA$ A. (a) What is the $\mathrm{Si}-\mathrm{Si}$ distance in this crystal? (b) Calculate the density of crystalline silicon.

Crystal Wang

Numerade Educator

Problem 98

$\Delta$ (a) What types of electromagnetic radiation are suitable for diffraction studies of crystals? (b) Describe the X-ray diffraction experiment. (c) What must be the relationship between the wavelength of incident radiation and the spacing of the particles in a crystal for diffraction to occur?

Crystal Wang

Numerade Educator

Problem 99

$\Delta$ (a) Write the Bragg equation. Identify each symbol. (b) $\mathrm{X}$ -rays from a palladium source $(\mathrm{I}=0.576 \AA$ \& were reflected by a sample of copper at an angle of $9.40^{\circ}$. This reflection corresponds to the unit cell length $(d=a)$ with $n=2$ in the Bragg equation. Calculate the length of the copper unit cell.

Lottie Adams

Numerade Educator

Problem 100

The spacing between successive planes of platinum atoms parallel to the cubic unit cell face is $2.256 \AA$. When X-radiation emitted by copper strikes a crystal of platinum metal, the minimum diffraction angle of X-rays is $19.98^{\circ}$. What is the wavelength of the Cu radiation?

Lottie Adams

Numerade Educator

Problem 101

Gold crystallizes in a fcc structure. When X-radiation of $0.70926$ \& wavelength from molybdenum is used to determine the structure of metallic gold, the minimum diffraction angle of X-rays by the gold is $8.683^{\circ} .$ Calculate the spacing between parallel layers of gold atoms.

Lottie Adams

Numerade Educator

Problem 102

In general, metallic solids are ductile and malleable, whereas ionic salts are brittle and shatter readily (although they are hard). Explain this observation.

Lottie Adams

Numerade Educator

Problem 103

What single factor accounts for the ability of metals to conduct both heat and electricity in the solid state? Why are ionic solids poor conductors of heat and electricity although they are composed of charged particles?

Lottie Adams

Numerade Educator

Problem 104

Compare the temperature dependence of electrical conductivity of a metal with that of a typical metalloid. Explain the difference.

Lottie Adams

Numerade Educator

Problem 105

Benzene, $\mathrm{C}_{6} \mathrm{H}_{6}$, boils at $80.1^{\circ} \mathrm{C}$. How much energy, in joules, would be required to change $450.0 \mathrm{~g}$ of liquid benzene at $21.5^{\circ} \mathrm{C}$ to a vapor at its boiling point? (The specific heat of liquid benzene is $1.74 \mathrm{~J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}$ and its heat of vaporization is $395 \mathrm{~J} / \mathrm{g} .$

Lottie Adams

Numerade Educator

Problem 106

The three major components of air are $\mathrm{N}_{2}\left(\mathrm{bp}-196^{\circ} \mathrm{C}\right)$, $\mathrm{O}_{2}\left(\mathrm{bp}-183{ }^{\circ} \mathrm{C}\right)$, and $\mathrm{Ar}$ (bp $\left.-186^{\circ} \mathrm{C}\right)$. Suppose we have a
sample of liquid air at $-200^{\circ} \mathrm{C}$. In what order will these gases evaporate as the temperature is raised?

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 107

Sample of liquid ethanol, osorbs $5.13 \times 10^{3} \mathrm{~J}$ of heat at its normal boiling point, $78.0^{\circ} \mathrm{C}$. The molar enthalpy of vaporization of ethanol, $\Delta H_{\text {vap }}$, is $39.3$ $\mathrm{kJ} / \mathrm{mol}$. (a) What volume of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$ vapor is produced? The volume is measured at $78.0^{\circ} \mathrm{C}$ and $1.00 \mathrm{~atm}$ pressure.
(b) What mass of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$ remains in the liquid state?A A $15.0$ -g sample of liquid ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$, absorbs $5.13 \times 10^{3} \mathrm{~J}$ of heat at its normal boiling point, $78.0^{\circ} \mathrm{C}$. The molar enthalpy of vaporization of ethanol, $\Delta H_{\text {vap }}$, is $39.3$ $\mathrm{kJ} / \mathrm{mol}$. (a) What volume of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$ vapor is produced? The volume is measured at $78.0^{\circ} \mathrm{C}$ and $1.00$ atm pressure.
(b) What mass of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$ remains in the liquid state?

Crystal Wang

Numerade Educator

Problem 108

A What is the pressure predicted by the ideal gas law for one mole of steam in $31.0 \mathrm{~L}$ at $100^{\circ} \mathrm{C}$ ? What is the pressure predicted by the van der Waals equation (Section $12-15)$ given that $a=5.464 \mathrm{~L}^{2} \cdot \mathrm{atm} / \mathrm{mol}^{2}$ and $\bar{b}=0.03049 \mathrm{~L} / \mathrm{mol}$ ?
What is the percent difference between these values? Does steam deviate from ideality significantly at $100^{\circ} \mathrm{C}$ ? Why?

Crystal Wang

Numerade Educator

Problem 109

A The boiling points of $\mathrm{HCl}, \mathrm{HBr}$, and HI increase with increasing molecular weight. Yet the melting and boiling points of the sodium halides, $\mathrm{NaCl}$, $\mathrm{NaBr}$, and NaI, decrease with increasing formula weight. Explain why the trends are opposite. Describe the intermolecular forces present in each of these compounds and predict which has the lowest boiling point.

Lottie Adams

Numerade Educator

Problem 110

The structures for three molecules having the formula $\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{Cl}_{2}$ are
Describe the intermolecular forces present in each of these compounds and predict which has the lowest boiling point.

Crystal Wang

Numerade Educator

Problem 111

Are the following statements true or false? Indicate why if a statement is false. (a) The vapor pressure of a liquid will decrease if the volume of liquid decreases. (b) The normal boiling point of a liquid is the temperature at which the external pressure equals the vapor pressure of the liquid. (c) The vapor pressures of liquids in a similar series tend to increase with increasing molecular weight.

Lottie Adams

Numerade Educator

Problem 112

Are the following statements true or false? Indicate why if a statement is false. (a) The equilibrium vapor pressure of a liquid is independent of the volume occupied by the vapor above the liquid. (b) The normal boiling point of a liquid changes with changing atmospheric pressure. (c) The vapor pressure of a liquid will increase if the mass of liquid is increased.

Lottie Adams

Numerade Educator

Problem 113

The following are vapor pressures at $20^{\circ} \mathrm{C}$. Predict the order of increasing normal boiling points of the liquids, acetone, 185 torr; ethanol, 44 torr; carbon disulfide, $\mathrm{CS}_{2}$, 309 torr.

Lottie Adams

Numerade Educator

Problem 114

Refer to Exercise $113 .$ What is the expected order of increasing molar heats of vaporization, $\Delta H_{\mathrm{vap}}$, of these liquids at their boiling points? Account for the order.

Crystal Wang

Numerade Educator

Problem 115

Refer to the sulfur phase diagram in Exercises 73 and 74 .
(a) Can rhombic sulfur be sublimed? If so, under what conditions? (b) Can monoclinic sulfur be sublimed? If so, under what conditions? (c) Describe what happens if rhombic sulfur is slowly heated from $80^{\circ} \mathrm{C}$ to $140^{\circ} \mathrm{C}$ at constant 1 -atm pressure. (d) What happens if rhombic sulfur is heated from $80^{\circ} \mathrm{C}$ to $140^{\circ} \mathrm{C}$ under constant pressure of $5 \times 10^{-6}$ atm?

Lottie Adams

Numerade Educator

Problem 116

The normal boiling point of ammonia, $\mathrm{NH}_{3}$, is $-33^{\circ} \mathrm{C}$, and its freezing point is $-78^{\circ} \mathrm{C}$. Fill in the blanks. (a) At STP $\left(0^{\circ} \mathrm{C}, 1 \mathrm{~atm}\right.$ pressure $), \mathrm{NH}_{3}$ is a
(b) If the temperature drops to $-40^{\circ} \mathrm{C}$, the ammonia will and be-
come a
(c) If the temperature drops further to $-80^{\circ} \mathrm{C}$ and the molecules arrange themselves in an orderly pattern, the ammonia will and become a
(d) If crystals of ammonia are left on the planet Mars at a temperature of $-100^{\circ} \mathrm{C}$, they will gradually disappear by the process of and form a

Crystal Wang

Numerade Educator

Problem 117

Give the correct names for these changes in state: (a) Crystals of para-dichlorobenzene, used as a moth repellent, gradually become vapor without passing through the liquid phase. (b) As you enter a warm room from the outdoors on a cold winter day, your eyeglasses become fogged with a film of moisture. (c) On the same (windy) winter day, a pan of water is left outdoors. Some of it turns to vapor, the rest to ice.

Lottie Adams

Numerade Educator

Problem 118

The normal boiling point of trichlorofluoromethane, $\mathrm{CCl}_{3} \mathrm{~F}$, is $24^{\circ} \mathrm{C}$, and its freezing point is $-111^{\circ} \mathrm{C}$. Complete these sentences by supplying the proper terms that describe a state of matter or a change in state. (a) At standard temperature and pressure, $\mathrm{CCl}_{3} \mathrm{~F}$ is a
(b) In an arctic winter at $-40^{\circ} \mathrm{C}$ and 1 atm pressure, $\mathrm{CCl}_{3} \mathrm{~F}$ is a If it is cooled to $-120{ }^{\circ} \mathrm{C}$, the molecules arrange themselves in an orderly lattice, the $\mathrm{CCl}_{3} \mathrm{~F}$ and becomes
a (c) If crystalline $\mathrm{CCl}_{3} \mathrm{~F}$ is held at a temperature of $-120^{\circ} \mathrm{C}$ while a stream of helium gas is blown over it, the crystals will gradually disappear by the process of . If liquid $\mathrm{CCl}_{3} \mathrm{~F}$ is boiled at atmospheric pressure, it is converted to a

Crystal Wang

Numerade Educator

Problem 119

The van der Waals constants (Section $12-15)$ are $a=$ $19.01 \mathrm{~L}^{2} \cdot \mathrm{atm} / \mathrm{mol}^{2}, b=0.1460 \mathrm{~L} / \mathrm{mol}$ for pentane, and
$a=18.05 \mathrm{~L}^{2} \cdot \mathrm{atm} / \mathrm{mol}^{2}, b=0.1417 \mathrm{~L} / \mathrm{mol}$ for isopentane.
<smiles>CCCCCC</smiles>
<smiles>CCC(C)(C)C</smiles>
pentane isopentane
(a) Basing your reasoning on intermolecular forces, why would you expect $a$ for pentane to be greater? (b) Basing your reasoning on molecular size, why would you expect $b$ for pentane to be greater?

Crystal Wang

Numerade Educator

Problem 120

What is contained in the bubbles formed during the boiling process?

Lottie Adams

Numerade Educator

Problem 121

- How can one convert a sample of a liquid to a vapor without changing its temperature?

Lottie Adams

Numerade Educator

Problem 122

Iodine sublimes at room temperature and pressure; water does not. Explain the differences you would expect to observe at room temperature if $7.5$ grams of iodine crystals were sealed in a 10.-mL container and $7.5 \mathrm{~mL}$ of water were sealed in a similar container.

Crystal Wang

Numerade Educator

Problem 123

Using ball-and-stick representations, draw a sketch similar to Figure $13-3$ of four molecules of HBr that indicates dipole-dipole forces between molecules.

Lottie Adams

Numerade Educator

Problem 124

Using space-filling representations, draw a sketch similar to Figure $13-3$ of four molecules of $\mathrm{HBr}$ that indicates dipole-dipole forces between molecules.

Lottie Adams

Numerade Educator

Problem 125

Referring to the phase diagram for carbon dioxide shown in Active Figure $13-17 \mathrm{~b}$ for approximate values, draw a heating curve similar to that in Active Figure $13-15$ for carbon dioxide at 1 atmosphere pressure. Draw a second heating curve for carbon dioxide at 5 atm pressure. Estimate the transition temperatures.

Crystal Wang

Numerade Educator

Problem 126

A popular misconception is that "hot water freezes more quickly than cold water." In an experiment, two $100 .-\mathrm{mL}$ samples of water, in identical containers, were placed far apart in a freezer at $-25^{\circ} \mathrm{C}$. One sample had an initial temperature of $78^{\circ} \mathrm{C}$, while the other was at $24^{\circ} \mathrm{C}$. The second sample took 151 minutes to freeze, and the warmer sample took 166 minutes. The warmer sample took more time but not much. How can you explain their taking about the same length of time to freeze?

Lottie Adams

Numerade Educator

Problem 127

Consider the portions of the heating curves shown here. Which compound has the highest specific heat capacity?

Lottie Adams

Numerade Educator

Problem 128

More than 150 years ago Pierre Dulong and A. T. Petit discovered a rule of thumb that the heat capacity of one mole of a pure solid element is about $6.0$ calories per ${ }^{\circ} \mathrm{C}$ (i.e., about $\left.25 \mathrm{~J} /{ }^{\circ} \mathrm{C}\right)$. A $100.2-\mathrm{g}$ sample of an unknown metal at $99.9^{\circ} \mathrm{C}$ is placed in $50.6 \mathrm{~g}$ of water at $24.8^{\circ} \mathrm{C}$. The temperature is $36.6^{\circ} \mathrm{C}$ when the system comes to equilibrium. Assume all heat lost by the metal is absorbed by the water. What is the likelv identity of this metal?

Lottie Adams

Numerade Educator

Problem 129

In a flask containing dry air and some liquid silicon tetrachloride, $\mathrm{SiCl}_{4}$, the total pressure was 988 torr at $225^{\circ} \mathrm{C}$. Halving the volume of the flask increased the pressure to 1742 torr at constant temperature. What is the vapor pressure of $\mathrm{SiCl}_{4}$ in this flask at $225^{\circ} \mathrm{C}$ ?

Lottie Adams

Numerade Educator

Problem 130

A friend comes to you with this problem: "I looked up the vapor pressure of water in a table; it is $26.7$ torr at $300 \mathrm{~K}$ and 92,826 torr at $600 \mathrm{~K}$. That means that the vapor pressure increases by a factor of 3477 when the absolute temperature doubles over this temperature range. But I thought the pressure was proportional to the absolute temperature, $P=n R T / V .$ The pressure doesn't just double. Why?" How would you help the friend?

Lottie Adams

Numerade Educator

Problem 131

Using as many as six drawings (frames) for each, depict the changes that occur at the molecular level during each of the following physical changes: (a) melting an ice cube;
(b) sublimation of an ice cube below $4.6^{\circ} \mathrm{C}$ and $4.6$ torr, and
(c) evaporation of a droplet of water at room temperature and pressure.

Crystal Wang

Numerade Educator

Problem 132

Write the Lewis formula of each member of each of the following pairs. Then use VSEPR theory to predict the geometry about each central atom, and describe any features that lead you to decide which member of each pair would have the lower boiling point. (a) $\mathrm{CH}_{3} \mathrm{COOH}$ and $\mathrm{HCOCH}_{3} ;$ (b) $\mathrm{NHF}_{2}$ and $\mathrm{BH}_{2} \mathrm{Cl} ;$ (c) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}$ and
$\mathrm{CH}_{3} \mathrm{OCH}_{3}$

Lottie Adams

Numerade Educator

Problem 133

At its normal melting point of $271.3^{\circ} \mathrm{C}$, solid bismuth has a density of $9.73 \mathrm{~g} / \mathrm{cm}^{3}$, and liquid bismuth has a density of $10.05 \mathrm{~g} / \mathrm{cm}^{3}$. A mixture of liquid and solid bismuth is in equilibrium at $271.3^{\circ} \mathrm{C}$. If the pressure were increased from 1 atm to $10 \mathrm{~atm}$, would more solid bismuth melt or would more liquid bismuth freeze? What unusual property does bismuth share with water?

Lottie Adams

Numerade Educator

Problem 134

The doping of silicon with boron to an atomic concentration of $0.0010 \%$ boron atoms vs. silicon atoms increases its conductivity by a factor of $10^{3}$ at room temperature. How many atoms of boron would be needed to dope $11.5 \mathrm{~g}$ of silicon? What mass of boron is this?

Crystal Wang

Numerade Educator

Problem 135

Using The Merck Index or Handbook of Cbemistry and Pbysics or a suitable site found on the web, look up the temperature at which caffeine sublimes at standard atmospheric pressure.

Crystal Wang

Numerade Educator

Problem 136

(a) On the web locate the temperature and the pressure at the triple point of carbon dioxide and compare the data that

Crystal Wang

Numerade Educator

Problem 137

Go to http://cst-www.nrl.navy.mil/lattice, and click on "cubic close packed," "fcc(A1)," and finally "see the structure from several perspectives."
(a) Draw the top view, and indicate which atoms are in the first layer and which are in the second layer. Why is the third layer not shown?
(b) Draw the front view, and indicate which atoms are in the first layer and which are in the second layer. Does the front view differ from the top view?

Crystal Wang

Numerade Educator

Problem 138

Open http://www.lyo-san.ca/english/lyophilisation .html. Using information at this site, at another site, or from reference books, compare the terms: lyophilization, freeze-drying, and sublimation.

Crystal Wang

Numerade Educator

Problem 912

Tungsten has a density of $19.3 \mathrm{~g} / \mathrm{cm}^{3}$ and crystallizes in a cubic lattice whose unit cell edge length is $3.16 \AA$. Which type of cubic unit cell is it?

Crystal Wang

Numerade Educator