unit 5

Question 1

gas properties

Answer 1

expand
low density
changes dramatically with a change in pressure/temp
volume, pressure, temperature are interrelated

Question 2

pressure

Answer 2

force exerted per unit area as gas molecules strike the surfaces around them

Question 3

unit equalities

Answer 3

760. mm Hg = 760. torr = 1 atm = 101.3 kPa = 14.7 psi

Question 4

mm Hg (millimeters of mercury)/torr

Answer 4

atmospheric pressure that can support a column of mercury that is 760. mm high in a barometer

Question 5

atmospheres (atm)

Answer 5

avg. pressure at sea level

Question 6

pascal (Pa)

Answer 6

SI unit of pressure
also expressed as kPa

Question 7

psi (lbs per square inch)

Answer 7

measure of force per unit area

Question 8

boyle’s law

Answer 8

p1v1=p2v2
volume increases = pressure decreases

Question 9

Charles law

Answer 9

v1/t1 = v2/t2
volume increases = temperature increases
always positive

Question 10

avogadro’s law

Answer 10

v1/n1 = v2/n2
volume increases = moles increase

Question 11

Gay-Lussac’s law

Answer 11

p1/t1 = p2/t2
pressure increases = temperature increases

Question 12

combined gas law

Answer 12

p1v1/t1 = p2v2/t2

Question 13

ideal gas law

Answer 13

PV = nRT

P: pressure in atm
V: volume in L
n: moles in mol
R: ideal gas constant (0.08206 when Latm/molK)
T: temperature in K

Question 14

molar volume

Answer 14

volume occupied by 1 mol of a substance

Question 15

standard temperature and pressure (STP)

Answer 15

for gases, molar volume is usually STP (1.00 atm)

Question 16

density =

Answer 16

molar mass / molar volume
molar mass increases = density increases

Question 17

1 mol of an ideal gas occupies:

Answer 17

22.4 L at STP

Question 18

density of a gas equation

Answer 18

d = PM / RT
d: density in g/L
P: pressure in atm
M: molar mass in g/mol
R: ideal gas constant (0.08206 when Latm/molK)
T: temperature in K

Question 19

to find molar mass of a gas:

Answer 19

measure mass and volume under known conditions of T and P
use ideal gas law to determine amount of gas in mol
divide mass by moles to get molar mass

Question 20

partial pressure

Answer 20

pressure due to an individual component of a gas
Pn = Nn RT/V

Question 21

Dalton’s Law of Partial Pressures

Answer 21

sum of partial pressures in a gas mixture = total pressure
P(total) = P(a) + P(b) + P(c)

Question 22

mole fraction (X(a))

Answer 22

X(a) = N(a)/N(total)

or

P(a) = X(a)P(total)

Question 23

gas mole fraction

Answer 23

percent by volume / 100

Question 24

Vapor pressure

Answer 24

gas mixture with partial pressures
temp increases = Vapor pressure increases

Question 25

kinetic molecular theory

Answer 25

simplest model for the behavior of gases

Question 26

KMT postulates

Answer 26

-negligibly small
-avg. kinetic energy is proportional to Kelvin temp
-collision of one particle with another is elastic

Question 27

pressure =

Answer 27

force / area

Question 28

Boyle’s law: proportion

Answer 28

volume is inversely proportional to pressure

Question 29

Charles law: proportion

Answer 29

volume is proportional to temperature

Question 30

Avogadro’s law: proportion

Answer 30

volume is proportional to moles

Question 31

particles of different masses have the (same/different) average kinetic energy

Answer 31

same

Question 32

kinetic energy =

Answer 32

(1/2)mv^2

Question 33

do lighter particles travel faster than heavier particles?

Answer 33

yes

Question 34

temperature and velocity distribution proportion

Answer 34

temp increases = higher velocity

Question 35

diffusion

Answer 35

gas molecules spread out due to a concentration gradient

-heavier molecules diffuse more slowly

Question 36

effusion

Answer 36

gas escapes from a container into a vacuum through a small hole

-heavier molecules effuse more slowly

Question 37

rate is inversely proportional to

Answer 37

1 / square root of the molar mass

Question 38

effusion rate a / effusion rate b =

Answer 38

square root of molar mass b / square root of molar mass a

Question 39

gases behave ideally when:

Answer 39

-volume of gas particles is small compared to the volume between them

-attractions between particles are insignificant

Question 40

finite volume

Answer 40

actual size

Question 41

when is finite volume important?

Answer 41

high pressure because then the particles occupy a significant portion of the total gas volume

Question 42

when are intermolecular forces important?

Answer 42

low temps: collisions occur with less kinetic energy and weak attractions decrease collisions, also causes a decrease in pressure

Question 43

Which postulate of the kinetic molecular theory breaks down under conditions of high pressure?

Answer 43

the volume of a gas particle is small when compared to the space between the particles