# Holt Chemistry

## Educators

TD

Problem 1

Most substances can be in three states. What
are they?

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Problem 2

Explain how solid naphthalene in mothballs
is distributed evenly through clothes in a
drawer.

TD
Theodore D.

Problem 3

What is the freezing point of a substance?

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Problem 4

Carbon tetrachloride, $\mathrm{CCl}_{4},$ is nonpolar.
What forces hold the molecules together?

TD
Theodore D.

Problem 5

Compare dipole-dipole forces and hydrogen
bonds.

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Problem 6

What is the difference between the terms
state and phase?

TD
Theodore D.

Problem 7

Define boiling point in terms of vapor
pressure.

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Problem 8

What is a triple point?

TD
Theodore D.

Problem 9

Compare the arrangement and movement
of particles in the solid, liquid, and gas states
of matter.

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Problem 10

What is surface tension?

TD
Theodore D.

Problem 11

A small drop of water assumes an almost
spherical form on a Teflon surface.
Explain why.

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Problem 12

What is happening when water is heated
from $25^{\circ} \mathrm{C}$ to $155^{\circ} \mathrm{C}$ ?

TD
Theodore D.

Problem 13

Give an example of deposition.

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Problem 14

Contrast ionic and molecular substances in
terms of the types of attractive forces that
govern their behavior.

TD
Theodore D.

Problem 15

Is the melting point of CaCl_ higher than
that of $\mathrm{NaCl}$ or lower? Explain your answer.

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Problem 16

A fellow student says, "All substances
experience London dispersion forces of
attraction between particles." Is this

TD
Theodore D.

Problem 17

Which has larger London dispersion forces
between its molecules, CF $_{4}$ or $\mathrm{CCl}_{4}$ ?

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Problem 18

Of the three forces, ionic, dipole-dipole, and
London dispersion forces, which is the
strongest?

TD
Theodore D.

Problem 19

Why does ice float in water even though
most solids sink in the pure liquid?

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Problem 20

Why does $\mathrm{CBr}_{4}$ boil at a higher temperature
than $\mathrm{CCl}_{4}$ does?

TD
Theodore D.

Problem 21

The molar enthalpy of fusion of water is
6.009 $\mathrm{kJ} / \mathrm{mol}$ at $0^{\circ} \mathrm{C}$ . Explain what this
statement means.

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Problem 22

Why is the molar enthalpy of vaporization
of a substance much higher than the molar
enthalpy of fusion?

TD
Theodore D.

Problem 23

How do you calculate the entropy change
during a change of state at equilibrium?

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Problem 24

Why is the entropy of a substance higher in
the liquid state than in the solid state?

TD
Theodore D.

Problem 25

At $100^{\circ} \mathrm{C},$ the enthalpy change for condensa-
tion of water vapor to liquid is negative. Is
the entropy change positive, or is it negative?

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Problem 26

$\Delta H$ for a process is positive, and $\Delta S$ is
negative. What can you conclude about
the process?

TD
Theodore D.

Problem 27

Explain why liquid water at 273.0 $\mathrm{K}$ will not
melt in terms of Gibbs energy.

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Problem 28

What thermodynamic values do you need
to know to calculate a substance's melting
point?

TD
Theodore D.

Problem 29

How does pressure affect the entropy of
a gas?

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Problem 30

How does pressure affect changes between
the liquid and vapor states?

TD
Theodore D.

Problem 31

You have sweetened iced tea with sugar,
and ice cubes are present. How many phases
are present?

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Problem 32

The term vapor pressure almost always
means the equilibrium vapor pressure. What
physical arrangement is needed to measure
vapor pressure?

TD
Theodore D.

Problem 33

What is meant by the statement that a liquid
and its vapor in a closed container are in a
state of equilibrium?

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Problem 34

As the temperature of a liquid increases,
what happens to the vapor pressure?

TD
Theodore D.

Problem 35

Use the above graph of the vapor pressure
of water versus temperature to answer the
following questions.

\begin{array}{l}{\text { a. At what point(s) does water boil at }} \\ {\text { standard atmospheric pressure? }} \\ {\text { b. At what point(s) is water only in the }} \\ {\text { liquid phase? }}\end{array}

\begin{array}{l}{\text { c. At what point(s) is water only in the }} \\ {\text { vapor phase? }} \\ {\text { d. At what point(s) is liquid water in }} \\ {\text { equilibrium with water vapor? }}\end{array}

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Problem 36

What two fixed points are on all phase
diagrams?

TD
Theodore D.

Problem 37

\begin{array}{l}{\text { The enthalpy of fusion of chlorine, } \mathrm{Cl}_{2}, \text { is }} \\ {6.40 \mathrm{kJ} / \mathrm{mol}, \text { and the entropy of fusion is }} \\ {37.2 \mathrm{J} / \mathrm{mol} \cdot \mathrm{K} \text { . }}\end{array}

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Problem 38

The enthalpy of fusion of sulfur trioxide is
8.60 $\mathrm{kJ} / \mathrm{mol}$ , and the entropy of fusion is
29.7 $\mathrm{J} / \mathrm{mol} \cdot \mathrm{K}$

TD
Theodore D.

Problem 39

The enthalpy of vaporization of butane,
$\mathrm{C}_{4} \mathrm{H}_{10},$ is 22.44 $\mathrm{kJ} / \mathrm{mol}$ , and the entropy of
vaporization is 82.2 $\mathrm{J} / \mathrm{mol} \cdot \mathrm{K}$ .

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Problem 40

$\Delta H_{v a p}$ for silicon tetrachloride is
$28.7 \mathrm{kJ} / \mathrm{mol},$ and $\Delta S_{\text {vap}}$ is 86.7 $\mathrm{J} / \mathrm{mol} \cdot \mathrm{K}$

TD
Theodore D.

Problem 41

The critical point for krypton is at $-64^{\circ} \mathrm{C}$
and a pressure of $5.5 \times 10^{3} \mathrm{kP}$ . The triple
point is at $-157.4^{\circ} \mathrm{C}$ and a pressure of
$73.2 \mathrm{kPa} . \mathrm{At}-172^{\circ} \mathrm{C}$ the vapor pressure is
13 $\mathrm{kPa}$ . The normal boiling point is
$-152^{\circ} \mathrm{C} .$ Sketch the phase diagram.

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Problem 42

The critical point for carbon tetrachloride is
at $283^{\circ} \mathrm{C}$ and $4.5 \times 10^{3}$ kPa. The triple point is
at $-87.0^{\circ} \mathrm{C}$ and 28.9 $\mathrm{kPa}$ . The normal boiling
point is $76.7^{\circ} \mathrm{C}$ . Sketch the phase diagram.

TD
Theodore D.

Problem 43

Calculate the melting point of acetic acid at
standard pressure. The enthalpy of fusion of
acetic acid is $11.54 \mathrm{kJ} / \mathrm{mol},$ and the entropy
of fusion is 39.8 $\mathrm{J} / \mathrm{mol} \cdot \mathrm{K}$ .

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Problem 44

$\Delta H_{v a p}$ for gold is $324 \mathrm{kJ} / \mathrm{mol},$ and $\Delta S_{\text {vap}}$ is
103.5 $\mathrm{J} / \mathrm{mol} \cdot \mathrm{K}$ . Calculate the boiling point
of gold.

TD
Theodore D.

Problem 45

The critical point for HBr is at $90^{\circ} \mathrm{C}$ and
$8.56 \times 10^{3}$ kPa. The triple point is at $-87.0^{\circ} \mathrm{C}$
and 29 $\mathrm{kP}$ . The normal boiling point is
$-66.5^{\circ} \mathrm{C} .$ Sketch the phase diagram.

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Problem 46

How can water be made to evaporate rap-
idly at room temperature?

TD
Theodore D.

Problem 47

How does a pressure cooker work?

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Problem 48

Which would have the higher boiling point:
chloroform, $\mathrm{CHCl}_{3},$ or bromoform, $\mathrm{CHBr}_{3}$ ?

TD
Theodore D.

Problem 49

You know that the enthalpy change for
vaporizing water is $\Delta H_{v a p}=H_{g a s}-H_{l i q}$
What is the Gibbs energy change for this
process?

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Problem 50

Explain why steam produces much more
severe burns than the same amount of boiling water does.

TD
Theodore D.

Problem 51

Chloroethane $\left(T_{b p}=-13^{\circ} \mathrm{C}\right)$ has been used
as a local anesthetic. When the liquid is
sprayed onto the skin, it cools the skin
enough to freeze and numb the skin.
Explain the cooling effect of this liquid.

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Problem 52

Is it possible to have only liquid water present in a container at $0.00^{\circ} \mathrm{C}$ ? Explain.

TD
Theodore D.

Problem 53

Consider a system composed of water
vapor and liquid at equilibrium at $100^{\circ} \mathrm{C}$ .
Do the molecules of $\mathrm{H}_{2} \mathrm{O}$ in the vapor have
more kinetic energy than molecules in the
liquid do? Explain.

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Problem 54

Look at the phase diagram for carbon
dioxide. How can $\mathrm{CO}_{2}$ be made to boil?

TD
Theodore D.

Problem 55

Liquid crystals are substances that have
properties of both liquids and crystals.
Write a report on these substances and
their various uses.

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Problem 56

Some liquids lose all viscosity when cooled
to extremely low temperatures - a phenomenon called superfluidity. Find out more about
the properties of superfluid substances.

TD
Theodore D.

Problem 57

Many scientists think that more than 99$\%$
of the known matter in the universe is
made of a fourth state of matter called
plasma. Research plasmas, and report your
findings to the class.

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Problem 58

must be made when cooking and baking at
high elevations. Collect instructions for high-
elevation adjustments from packages of prepared food mixes. Explain why changes must
be made in recipes that will be prepared at
high elevations. Check your library for cook-books that contain information about food
preparation at high elevations.

TD
Theodore D.

Problem 59

Use the following terms to create a concept
map: boiling point, liquids, vapor pressure,
gases, melting point, states, and equilibrium.

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Problem 60

What is the normal boiling point of
water?

TD
Theodore D.

Problem 61

Give the coordinates for a point at
which only liquid water is present.

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Problem 62

Give the coordinates for a point at
which liquid water is in equilibrium
with vapor.

TD
Theodore D.

Problem 63

Give the coordinates for a point at
which only vapor is present.

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Problem 64

What is the vapor pressure of water at
point $\mathrm{E} ?$

TD
Theodore D.

Problem 65

What will happen if the vapor at
point $D$ is cooled at constant pressure?

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Problem 66

Calculating Vapor Pressure by Using a Table
The graphing calculator can run a program
that calculates a table for the vapor pressure
in atmospheres at different temperatures (K)
given the number of moles of a gas and the
volume of the gas (V). Given a 0.50 mol gas
sample with a volume of $10 \mathrm{L},$ you can calculate the pressure at 290 $\mathrm{K}$ by using a table.
Use this program to make the table. Next,
use the table to perform the calculations.
Go to Appendix C. If you are using a TI- -83
VAPOR and data and run the application as
directed. If you are using another calculator,
your teacher will provide you with key-
strokes and data sets to use. After you have
run the program, answer the questions.
a. What is the pressure for 1.3 mol of a gas
with a volume of 8.0 $\mathrm{L}$ and a temperature
of 320 $\mathrm{K} ?$
b. What is the pressure for 1.5 mol of a gas
with a volume of 10.0 $\mathrm{L}$ and a temperature of 340 $\mathrm{K} ?$
Two gases are measured at 300 $\mathrm{K}$ . One
has an amount of 1.3 $\mathrm{mol}$ and a volume of
$7.5 \mathrm{L},$ and the other has an amount of
0.5 $\mathrm{mol}$ and a volume of 10.0 $\mathrm{L} .$ Which
gas has the lesser pressure?

TD
Theodore D.