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29 Cards in this Set

  • Front
  • Back

-ideal gas law




-two prostulates of the ideal gas law

-predicts the relationship between pressure volume and temperature and amount of gas




1)gas molecules have zero volume




2)there are zero intermolecular forces between bass molecules



gas constant (R)

measure of thermal energy in a gas

STP






SATP

STP


T=273.15K (0 degrees)


P=1 bar




SATP


T= 298.15k (25 degrees)


P= 1 bar



getting concentration from ideal gas law

n/v - concentration (moles over volume)




therefore: P/RT =concenteration

density using ideal gas law

(mass over volume)




P/RT = (n.M)/v





daltons law of partial pressure

states that we can consider each gas in a mixture independently.




total pressure is just the sum of all partial pressures

partial pressure is proportional to

concentration

partial pressure when collisions are reactive and non reactive

when collisions are non reactive it does not matter what two molecules collide. gas mixtures behave the same as pure gas.




when collisions are reactive, the partial pressure of the entities is important .





as altitude increases temperature

first decreases... then starts to increase (most likely due to the ozone) then decreases again and starts to increase again ( this time most likely reaching the end of the atmosphere)

as altitude increases pressure

decreases

relative humidity (RH)

is a measure of the amount of water vapour in the air




Pressure increases as temperature increases

Ptotal =

Pdry air+ ph20




(important in solving questions)

acid rain

produced because of nitrogen and sulfur combustion

energy:




E*=


Erms=

all entities have energy by virtue of their temperature




E= 2.45 kj/mol




Erms=3.72kj/mol

Kinetic molecular theory (KM)




three points

the KM theory explains the gas laws




points: 1) gas consists of molecules with a mass "m" and a diameter "d" in constant random motion


2) molecular diameter is negligible in comparison to the distance between molecules.


3) all collisions are elastic there is no loss of kinetic energy and no reaction









maxwell Boltzmann distribution

energy collisions redistribute the thermal energy between colliding entites

drawing the maxwell boatsman distribution for velocity, order from highest peak to lowest

o2, n2 h2o, he , h2

temperature thermodynamics perspective

measure of rms energy in a substance (thermal energy)

pressure caused by




increases with

caused by molecules colliding with the walls of the container




pressure increases with more gas: collisions are more frequent




higher temperature- gasses hit the wall with more energy

diffusion

passage of gas through another substance along a concentration gradient




in hot water is faster---> more energy

effusion

passage of a gas through a small orifice (hole) into a vacuum

real gasses


recall the two postulates of the ideal gas law




not true anymore

real molecules have finite volume.


zero volume postulate fails at high pressure






have attractive intermolecular forces


zero intermolecular postulate fails at low temperature ( low temperature gas condenses

compressibility Z

is a measure of the non ideal behaviour of gas




Z= PV / nRT




look at compressibility chart

van der waals equation




Parameter "b"




b gets bigger as the

approximately corrects for the failings of the ideal gas law




finite volume: assume each mole of gas molecules occupy volume "b"




Vactual = Vcontainer - nb




as the molecule gets bigger

parameter "a" in van der waals equation

intermolecular forces: the parameter "a" accounts for the intermolecular interactions




Pobserved = Pideal - a(n/v)^2




n/v -----> concenteration

van der walls equation

formula sheet gasses section third equation left side

entities at the wall experience

net attractive forces towards the other entities

how does "a" and "b" effect pressure

rearrange van der walls equation to se this clearly.




"a" causes pressure to go down

when doing van der walls questions

pay attention to the units -----> use the right value for R everything should cancel.