chapter 8: Gases Flashcards
what are the percentages of gases in the air
N2 = 78 O2 = 21
the air we breathe is a…
mixture of gases
what are some characteristics of gases
- Spontaneously expand to fill their containers (no outside energy)
- highly compressible
- homogenous mixture
- low density
what happens when the gas particles collide with each other
creates pressure
what is pressure
force that results from the collisions
of gas particles divided by the area of the surface
with which they collide
what is the formula for pressure
P = F/A force = m x a
what does pressure depend on
of gas particles
fewer gas particles =
lower pressue
how does altitude affect pressure
pressure decreases above 30 k
- keep cabins pressurized
how does gravity affect the atomosphere
causes the atmosphere as a whole to press down on earth
what is atmospheric pressure
weight of air per unit of area
what is the si unit for force
newton (N)
what is the SI unit of pressure
N/m^2 or pascal (Pa)
who was pascal named after
Blaise Pascal
what is bar
used to report pressure; 10^5 Pa
who discovered atm,torr, mmhg
evangelista torricelli ( Galileo’s student)
who invented the mercury barometer
torricellu
what is standard atomospheric pressure
pressure @ sea lvl
what is the standard atms. press.
101325 Pa or 101.325 kPa
what non si units are w/ the atmospheric pressure
atm, mmhg m torr
what is a mamometer
measure pressure of enclosed gases
what did robert boyle do
investigated the relationship between the pressure
of a gas and its volume.
what was boyle’s law
volume and pressure are inverse @ constant temp
boyle’s law formula
P1V1 = P2V2
what did jacques charles do
discovered relationship between volume and temp
what was charles law
volume and temp are proportional @ maintained pressure
charles law formula
V1/T1 = V2/T2
what did gay lussac do and who was he
discovered relationship between gas and volume
law of combining volumes
what is the law of combining volumes
given P and T, the Vs of gases that react with
one another are in the ratios of small whole numbers
example: wo volumes of H2 gas react with one volume
of O2 gas to form two volumes of water vapor.
avogadro’s hypothesis
equal volumes of gases at the same temp and pressure have equal # of molecules
what are stp conditions
22.4 L
0 degrees celcius
1 atm
22.4 L =
6.022 x 10^23 molecules = 1 mol
avogadro’s law
volume is directly proportional to # of moles
(temp, pressure = constant_
what is the ideal gas equation
pv = nrt
what is an ideal gas
hypothetical gas whose pressure,
volume, and temperature behavior is completely
described by the ideal-gas equation.
what does R = in pvnrt
0.08206 L-atm/mol K
avogadro’s law formula
V1/n1 = V2/n2
pressure volume and temp formula
P1V1/T1 = P2V2/T2
what is the formula for density
d = m/V
moles per unit of volume =
P /RT
what is the formula for partial pressure
P = n1RT/V
what does p total =
RT/V
mole fraction x
n1/ntotal
P1 = (n1/ntotal)Ptotal = X1Ptotal
how is gas collected
through water displacement
what does vapor pressure depend on
temp
what does the ideal gas law show and what does it lack
how gases behave but doesn’t explain why they behave like that
kinetic molecular theory describes…
model to help us picture what
happens to gas particles as
experimental conditions change.
what is the kinetic molecular theory
- ) volume = zero
- ) particles in constant motion
- ) particles have no force
gases in the same container have the same temp….
have the same average kinetic enegy
lighter particles =
faster average velocity
as temp increases
average velocity increases
what is diffusion
spread of a substance throuhout a space or second substance
what direction do gas molecules travel in
straight line
mean free path
avg distance a molecule travels between collisions
mean free path decreases as
pressure increases
Black Friday = Crowded = high pressure = short distance
before bumping into someone = short mean free path
‒ Mall after closing = low pressure = long distance before
bumping into someone = long mean free path
effusion
escape of gas molecule through tiny hole
characteristics of ideal gas law
- no attraction between has molecules
- gas molecules do not take up space
what conditions are ideal gas laws valid in
high temp low pressure
what is van de waals equation
n^2a/ V2
