Chapter 1: 1.2 The Ideal Gas Law

Question 1

Avogadro’s law states that one mole of any ideal gas always…

Answer 1

Occupies the same volume at a given temperature and pressure, regardless of the gas in question

Question 2

According to Avogadro’s Law, equal volumes of different gases at the same temperature and pressure…

Answer 2

Contains the same number of moles

Question 3

Define:

Molar volume of a gas

Answer 3

Volume occupied by one mole of any gas

Question 4

Define:

STP

Give units

Answer 4

Standard temperature and pressure

= 1 atm (101.324 kPa) and 273.15 K

Question 5

Define and state the formula for:

Density

(in terms of gases)

Answer 5

Mass per unit volume
d = m/V

Question 6

Show the relation and state the formula for:

Mass, molar mass, and moles

Answer 6

m = MM * n

Question 7

What are the two forms of the ideal gas equation that can be used to derive relationship between gas density and its molar mass?

Answer 7

d = (MM)P / RT

OR

MM = dRT / P

Question 8

State the relationships between gas density/molar mass at constant temperature

Answer 8

Gas density is directly proportional to its pressure

Question 9

State the relationships between gas density/molar mass at constant temperature AND pressure

Answer 9

Density is related to molar mass of the gas

Question 10

Define and state the formula for:

Dalton’s Law of Partial Pressures

Answer 10

A mixture of gases behaves as a single gas
PV = nRT or P(total) * V(total) = n(total) * R * T

Question 11

Define:

Dalton’s Law of Partial Pressures

Answer 11

The total pressure exerted by a mixture of gases is the sum of all the partial pressures of these gases

Question 12

State the formula for:

Mole fraction of any one gas in a mixture

Answer 12

X(i) = n(i)/n(T)
[mole fraction = # of moles of individual constituent / # of total moles in mixture]

Question 13

State the proportionality in:

Mole Fractions

State constants

Answer 13

Pressure (P) is directly proportional to moles (n)

At constant temperature (T) and volume (V)

Question 14

What must the mole fraction (ratio) equal to?

Answer 14

Must equal to the pressure ratio

Question 15

What does the sum of all mole fractions equal?

Answer 15

1

Question 16

At constant temperature and pressure, what is the relation between volume and moles?

Answer 16

Directly proportional

Question 17

Define:

Vapour pressure

Answer 17

The partial pressure of water vapour

Question 18

What does the vapour pressure of water depend on?

Answer 18

Only depends on the temperature of the water

Question 19

Does higher temperature mean more or less vapour pressure?

Answer 19

More

Question 20

Define:

Boiling point

Answer 20

Temperature at which the vapour pressure equals the atmospheric pressure

(Explains why water boils at lower temperatures at higher altitudes)

Question 21

True or False:

Solvents that are more volatile (have lower boiling points) have lower vapour pressures

Answer 21

False, solvents that are more volatile have higher vapour pressures

Question 22

Define:

Average Molar Mass of a mixture of different gases

Answer 22

The weighted average of the molar masses of the different components

Question 23

State the formula for:

Average molar mass of a gas mixture

Answer 23

MM (with a line above to represent weighted average) = XaMMa + XbMMb + XcMMc …

Question 24

State the assumptions of:

Kinetic Molecular Theory of Gases

Answer 24

1. Size of particles is negligible
2. Molecules are point particles (only Ek)
3. Elastic collisions
4. No intermolecular forces
5. Kinetic energy (Ek) is proportional to temperature (Ek [line above] = 1/2mu^2 [u has line])

Question 25

What do bars/lines above values mean?

Answer 25

Average values

Question 26

What does the term u[bar]^2 mean? How is it found?

Answer 26

Mean-square speed
Found by taking an average of the squares of the speeds of the molecules

Question 27

What are the factors that determine the pressure of a gas in a container?

Answer 27

1. Mass of each molecule (m)
2. Speed of the molecules (u)
3. Frequency of collisions/the number of collisions per second

Question 28

What does the frequency of collision relate to?

Answer 28

1. The number of molecules (N)
2. The volume of the container (V)
3. The speed of the molecules (u)

Question 29

State:

The basic equation of the kinetic theory of gases

Answer 29

P = 1/3 (N/V)(mu[bar]^2)

Question 30

State the proportionalities of:

Mean-square speed of gas molecules, temperature, molar mass

Answer 30

Directly proportional to the temperature
Inversely proportional to the molar mass

Question 31

True or False:

If a gas is heated the molecules will move faster

Answer 31

True

Question 32

True or False:

If two gases are at the same temperature, the lighter gas molecules move slower, on average, then the heavier gas molecules

Answer 32

False, the lighter gas molecules move faster, on average, than the heavier gas molecules

Question 33

What does the Maxwell-Boltzmann distribution govern?

Answer 33

The distribution of the speeds of the molecules

Question 34

State the term and formula for:

The more commonly used form of the mean-square speed term

Answer 34

Root-mean-square (rms) speed
(sqrt)(3RT/MM)

Question 35

State the proportionality between:

rms speed and square root ratio of molar masses

Answer 35

The rms speed for the two gases is inversely proportional to the square root of the ratio of their molar masses

Question 36

What are the units for rms speed? In this scenario, state the units for molar mass and R

Answer 36

rms speed: metres per second
Molar mass: kilograms
R: 8.314 J/mol K OR 8.314 kg m^2/s^2 mol K

Question 37

Define:

Effusion

Answer 37

The flow of gas molecules at low pressures through tiny pores or pinholes in a container

Question 38

What is the rate of effusion defined as?

Answer 38

Number of moles of the gas escaping the container per unit of time

Question 39

State:

Graham’s Law

Answer 39

The rate of effusion of a gas is inversely proportional to the square root of its molar mass

Question 40

State the proportionality of:

Rate of effusion, Molar Mass

Answer 40

Rate of effusion is inversely proportional to the square root of its molar mass

r(effusion) proportional to 1/(sqrt)MM

Question 41

How is Graham’s Law written when two gases A and B with equal partial pressure effuse through a porous material or a small hole?

Answer 41

r(A)/r(B) = (sqrt)[ MM(B) / MM(A) ]

Question 42

True or False:

Lighter molecules effuse faster than heavier molecules

Answer 42

True

Question 43

What is the special about the gas that emerges from the container in effusion?

Answer 43

It is enriched in the lighter component

Question 44

What does the quantity f = (sqrt) [MM(B) / MM(A)] called?

Answer 44

Enrichment factor (how much of one gas is part of the effusion)