Unit 6- The Gaseous State Flashcards
solid
has fixed shape and volume
units: g/cm^3 or g/mL
liquid
has fixed volume but no definite shape
unit: g/mL
gas
has no fixed volume or def shape
unit: g/L
pressure
force per unit area exerted on a surface
unit: 1Pa = 1kg/ ms^2
barometer
used to measure pressure of atmos
- height(h) = 760mm at normal atmos pressure
manometers
both open and closed end manometers measure pressure diffs
- pg>pa (h=pg-pa)
- pg<pa (h=pa-pg)
- h=pg
Boyle’s Law
V = k x 1/p
PV = K (if T and n are same)
*P1V1 = P2V2
Charles’ Law
V = k2 x T
0K = -273.15C
T in kelvin
*V1/T1 = V2/T2
Avogadro’s Law
V= k3 x n(mol)
*V1/n1 = V2/n2 (const T and P)
Ideal Gas Law
PV=nRT
R= 0.08206 Latm/molK
- vol of 1 mol at STP (T=0C P=1atm) = 22.4L
MM
(mass x R x T) / (P xV)
Density
(MM x P) / (R x T)
coeff
= L w/ const temp and pressure
Dalton’s Law of Partial Pressures
Pt=Pa+Pb
mole fraction (x, chi)
the # of mol of 1 component of a mix divided by the total # of mols of all substances present in the mix
Xa= na/ na + nb +nc…
Partial Pressure
Pa = Xa x Pt
Collecting gas over water
Pg = Pt - Ph2o
Kinetic Molec Theory of Gases
1) No forces of attraction or repulsion between gas particles
2) size of gas particles can be negligible
3) No loss in KE occurs when gas particles collide
4) KE changes only if T changes
Avg speed
- called the root mean square (rms) speed, Urms
- the square root of the avg squared speed
Urms =
sqaure root of (3RT/ MM)
*R= 8.314 kgm^2/s^2molK
- MM= kg/mol
Effusion
the passage of gas through a small hole into an evacuated space
* gases with low MM effuse more rapidly
diffusion
the mixing of particles due to motion
Graham’s Law of Effusion
relative rates of effusion can be used to determine MM (M)
rate of effusion A/ rate of effusion B = square root of (Mb/Ma)
Graham’s law when equal vol or pressure of gas A and B are used
effusion time (t)
tb/ ta = square root of (Mb/ Ma)
deviations from Ideal Behavior
at high pressures:
- ideal gas law fails
- kinetic molec theory fails (forces of attraction)
- assumption gas particles are small compared to distances between them fails
Van der Waals Equation
corrects for attractive forces and vol occupied by gas molec
(P + an^2/v^2)(V-nb) = nRT
- a = const relat to strenght of attraction forces
- b = const that depends on the size of the gas particles
