Chapter 10 Concepts

Question 1

Boyle’s Law (description)

Answer 1

As constant mass and temperature, the pressure and volume are inversely proportional (as pressure increases, volume decreases).

Question 2

Boyle’s Law (equation)

Answer 2

PiVi = PfVf

Question 3

Charles’ Law (description)

Answer 3

The volume of a fixed mass of gas at constant pressure is directly proportional to its Kelvin temperature (as temperature increases, volume increases).

Question 4

Charles’ Law (equation)

Answer 4

Vi/Ti = Vf/Tf

Question 5

Gay-Lussac’s Law (description)

Answer 5

The pressure of a fixed amount of gas, at constant volume, is directly proportional to its Kelvin temperature.

Question 6

Gay-Lussac’s Law (equation)

Answer 6

Pi/Ti = Pf/Tf

Question 7

Combined gas law (equation)

Answer 7

PiVi/Ti = PfVf/Tfu

Question 8

Avogadro’s Law (description)

Answer 8

Equal volumes of all ideal gases at the same temperature and pressure contain the same number of moles/molecules (as number of moles increases, the volume increases).

Question 9

Avogadro’s Law (equation)

Answer 9

ni/Vi = nf/Vf

Question 10

Molar volume

Answer 10

Mv = V/n (volume/number of moles: L/mol)

Question 11

Molar volume of ideal gas as STP

Answer 11

22.4 L/mol

Question 12

Kinetic-Molecular Theory

Answer 12

1) Gases consist of large numbers of molecule in continuous, random motion.
2) Gas molecules have insignificant volume of their own (compared to the total volume of the container they are in)
3) Molecules have no significant forces between each other or the container they are in
4) Collisions are completely elastic and thus do not use up energy
5) The average kinetic energy of the molecules is proportional to the absolute temperature.

Question 13

Effect of a volume increase at constant temperature

Answer 13

• Average kinetic energy of molecules remains unchanged
• Average speed/rms speed is unchanged
• Greater distance between molecules/fewer collisions, so pressure decreases

Question 14

Effect of a temperature increase at constant volume

Answer 14

• Average kinetic energy/rms speed increases

* More collisions with walls of container means increased pressure.

Question 15

Effect of molar mass on molecular speeds

Answer 15

Molecules with lower molecular masses have higher rms/average speeds.

Question 16

Effusion

Answer 16

The escape of gas molecules from a container through a hole into an evacuated space (only happens when they happen to hit the hole).

• So rate of effusion is directly proportional to the rms/average speed of the molecules.
• Size of molar mass also affects rate of effusion - lower molecular weight molecules escape faster than higher molecular weight molecules.

Question 17

Diffusion

Answer 17

The spread of one substance throughout a space or throughout a second substance. (such as the scent of perfume throughout a room)

• Slower than molecular speeds due to collisions.
• Faster for lower mass molecules than for higher mass ones.

Question 18

van der Waals equation (purpose of it)

Answer 18

As real gases compress with lower temperatures, there will be attractive forces between them, resulting in gases liquefying. Gases at high pressures cannot use ideal gas equation to predict pressure-volume properties either. Equation helps to predict behavior of real gases. Accounts for attractive forces between gas molecules and molecular volumes.

Question 19

van der Waals equation corrections

Answer 19

• Constant a - measure of how strongly the gas molecules attract each other. (because attractive forces between molecules tend to reduce the pressure)
• Constant b - measure of small but finite volume occupied by the gas molecules themselves. (because molecules don’t have the whole volume to move in, but only the space not already occupied by the other molecules)

Question 20

Density

Answer 20

D = m/V (mass per volume: g/L)

Question 21

Molar mass

Answer 21

Mm = m/n (mass per number of moles: g/mol)

Question 22

STP

Answer 22

273.15 K, 1.00 atm

Question 23

Dalton’s Law of Partial Pressure

Answer 23

Ptotal = P1 + P2 + P3 + … + Pn

Question 24

1 atm = ? mm Hg

Answer 24

760

Question 25

1 atm = ? torr

Answer 25

760

Question 26

1 atm = ? psi

Answer 26

14.7

Question 27

1 mm Hg = ? torr

Answer 27

1

Question 28

Density (d)-Molar mass (M) Equation

Answer 28

PM = dRT
d = m/V = PM/RT

Question 29

Gas constant (R)

Answer 29

0.08206 L-atm/mol-K

Question 30

Ideal Gas Equation

Answer 30

PV=nRT

Question 31

Molar mass (M)-Density (d) Equation

Answer 31

M = dRT/P

Question 32

To find only the pressure of a desired gas collected over water…

Answer 32

…one must subtract the vapor pressure of water from the total pressure

Question 33

Average kinetic energy relates to rms (root mean square speed) how?

Answer 33

Equal to the square of the rms. As temperature increases, the average kinetic energy increases, and the rms increases by its square.