Chapter 5

Question 1

Physical Characteristics of Gases

Answer 1

assume the volume and shape of their
containers.
• much lower densities than liquids and
solids.
• most compressible state of matter.
• mix evenly and completely when
confined to the same container.
• differ from liquids and solids –
for a gas, the pressure, volume,
temperature and the amount are
related.

Question 2

Pressure

Answer 2

The force exerted per unit area

Question 3

Barometer

Answer 3

a device for measuring

the pressure of the atmosphere.

Question 4

Manometer

Answer 4

a device for measuring the pressure of a gas or

liquid in a vessel.

Question 5

Empirical Gas Laws

Answer 5

All gases behave quite simply
with respect to:
temperature
pressure
volume
molar amount

Question 6

At one
atmosphere
the volume of
the gas is

Answer 6

100 mL

Question 7

When pressure is doubled, the volume is halved to

Answer 7

50 mL

Question 8

When pressure
is tripled, the
volume
decreases to

Answer 8

33 mL

Question 9

As P (h) increases, V

Answer 9

decreases

Question 10

Boyle’s Law

Answer 10

The volume (V) of a sample of gas at
constant temperature varies inversely with the applied
pressure (P).

Question 11

As T increases

Answer 11

V increases (think of a cold balloon)

Question 12

absolute zero in degrees c

Answer 12

-273.15°C

Question 13

absolute zero definition

Answer 13

It is the temperature at which the volume of a gas is
hypothetically zero.
This is the basis of the absolute temperature scale, the
Kelvin scale (K)

Question 14

Charles’s Law

Answer 14

The volume of a sample of gas at
constant pressure is directly proportional to the absolute
temperature (K).

Question 15

Avogadro’s Law

Answer 15

Equal volumes of any two gases contain the same number of

molecules (at the same temperature and pressure).

Question 16

Equal volumes of any two gases at the same temperature

and pressure contain the same number of

Answer 16

molecules…

but will have different masses.

Question 17

Standard Temperature and Pressure (STP)

Answer 17

exactly 0°
C
exactly 1 atm pressure
The reference condition for gases (chosen by convention)

Question 18

At STP, 1 mole of an ideal gas occupies

Answer 18

22.414 L

Question 19

the following are the

more commonly encountered R values

Answer 19

R = 0.08206 L atm K-1 mol-1
R = 62.36 L mmHg K-1 mol-1
R = 8.315 J K-1 mol-1

Question 20

The volume of a gas varies with temperature and pressure -

therefore, the density of a gas

Answer 20

also varies with temperature and pressure.

Question 21

Dalton found that in a mixture of unreactive gases

Answer 21

each
gas acts as if it were the only gas in the mixture as far as pressure is
concerned

Question 22

Dalton’s Law of Partial Pressures

Answer 22

The sum of the partial pressures of all the different gases in a mixture is
equal to the total pressure of the mixture:
Ptotal = PA + PB + PC + . . .

Question 23

Mole fraction

Answer 23

The composition of a gas mixture is often described in

terms of the component gases.

Question 24

Kinetic-Molecular Theory (Kinetic Theory)

Answer 24

A theory, developed by physicists, that is based on the
assumption that a gas consists of molecules in constant
random motion.

Question 25

The interpretation of a gas in terms of the kinetic molecular theory leads to

Answer 25

the ideal gas law.

Question 26

Until mid nineteenth century:
The popular view at that time (developed by
Newton) was that gas pressure was due to
the

Answer 26

mutual repulsions of the gas particles

that pushed them against the walls

Question 27

Present explanation of gas pressure:
According to kinetic theory, gas pressure is
the result of the

Answer 27

bombardment of the
container walls by constantly moving
molecules (Maxwell Boltzmann)

Question 28

Kinetic Molecular Theory of Gases: The Postulates (5)

Answer 28

Gases are composed of molecules whose sizes are negligible
compared with the average distance between them.

Molecules move randomly in straight lines in all directions and at
various speeds.

4. When molecules collide with each other, the collisions are
   elastic.
5. The average kinetic energy of the molecules is proportional to
   the temperature of the gas (Kelvin).

Question 29

An elastic collision is one in which

Answer 29

no kinetic energy is

lost (newton’s craddle)

Question 30

The frequency of collision is proportional to the

Answer 30

average speed, u, and the number of molecules,

N, and inversely proportional to the volume, V.

Question 31

The average momentum (mu) depends on the

Answer 31

mass of the molecules, m, and

its average velocity, u

Question 32

Molecular Speeds:

According to kinetic theory

Answer 32

molecular speeds vary over a wide range of values.
• The distribution depends on temperature, so it increases as the
temperature increases.

Question 33

Root-Mean Square (rms) Molecular Speed, u:

Answer 33

urms is a type of average molecular speed, equal to the speed of a
molecule that has the average molecular kinetic energy.

Question 34

Gas diffusion

Answer 34

is the gradual mixing of molecules of one gas with molecules

of another by virtue of their kinetic properties.

Question 35

Effusion:

Answer 35

The process by which a gas flows through a small hole in a

container. A pinprick in a balloon is one example of effusion.

Question 36

Graham’s Law of Effusion

Answer 36

The rate of effusion of gas molecules through a particular hole is
inversely proportional to the square root of the molecular mass of
the gas (at constant temperature and pressure).

Question 37

Real Gases: Deviations from Ideal Behavior

Answer 37

At high pressure, the volume of the gas molecule (Postulate 1) is not
negligible.

At high pressure, the intermolecular forces (Postulate 3) are not negligible

Question 38

Real gases do not follow

Answer 38

PV = nRT perfectly.
The van der Waals equation corrects for the non-ideal nature of real
gases.

Question 39

Van der Waals Equation

Answer 39

An equation that is similar to the ideal
gas law, but which includes two constants, a and b, to account for
deviations from ideal behavior