Chapter 6 Flashcards
SI unit for pressure
Pascal(PA) N/m^2 or j/m^3
bar and Pa conversion
1 bar=1•10^5 Pa
atm to bars and Pa
1atm=101,325 Pa=1.01325 bar
atm to mm Hg and torr
1atm=760 mm Hg=760 torr
Forces that affect barometers
gravity and atmospheric pressure
Manometer
used to measure pressure of a gas by opening and closing a valve separating the sample gas and mercury pushed down by the Patm. closed end measures gases less than Patm and open end measures gases more than Patm
Boyle’s law
P=1\V, P1V1=P2V2
Charle’s law
V1/T1=V2\T2, density decreases as temp increases
Avogadro’s law
V1/n1=V2/n2
Amonton’s\Gay-Lussac’s law
P1\T1=P2\T2
Change of state when amount of gas changes equation
P1V1/(n1T1)=P2V2/(n2T2)
Change of state with fixed amount of gas equation
P1V1/T1=P2V2/T2
Molar volume
volume occupied by one mole of a gas at STP
Density of a gas
d=m/v=PM/RT with p in atm and d in g/L
what does buoyancy depend on
molar masses and temperature
Density formula
d=(molar mass)p/RT
Concentration formula
c=n/v=p/RT
Molar mass formuls
molar mass=mRT/PV=dRT/P
mole fraction
xi=ni/ntotal
add up to 1
Kinetic molecular theory
Assumed that gas molecules
- Have tiny volumes compared with the collective volume they occupy
- Move constantly and randomly
- Have average kinetic energy proportional to absolute temp.
- Engage in elastic collisions with walls of container and other gas molecules
- Act independently of other gas molecules
Root mean square speed of molecules
u=_/(3RT/M)
Effusion
the process by which a gas escapes from a container through a tiny hole into a region of lower pressure
Graham’s law of effusion
rate of effusion=1/square root of molar mass, applicable when the diameter of the hole is substantially smaller than the average distance that a gaseous particle travels between collisions
Diffusion
spread of one substance through another
How do gas particles act at higher pressures vs STP?
At high P and low V, Vgas is not negligible, and attractive forces between gas molecules are significant
Van der Waals equation
P=nRt/(V-nb) - an^2/V^2
What is the purpose of a and b in van der Waal’s equation?
a: corrects for attractive forces that affect pressure
b: corrects for volume occupied by molecules
