This weekend, Daylight Saving ends. I get an hour of
sleep, you get an extra hour to study for the final.
Bizarro By Dan Piraro
Read sections 5.5, 5.6, 12.3
Practice PS #5 is posted 1 2
Ideal gas law useful for ordinary conditions. See table 5.3 from Silberberg
Ideal gas law is accurate to ~1.5% for gases under 20
atm AND 50C above their boiling points.
Molar volume at STP Vm = 22.414 L
STP = standard temperature and pressure (for gases)
0C and 1 atm
See fig 5.23 Temperature effect
Compressibility factor Z = = m
Essentially, we are plotting the deviation from the
ideal gas law. 5 6
The closer a gas is to the liquid state the more it will The most famous equation is the van der Waals
deviate from the ideal gas law. equation.
(P+ V2 )(V – nb) = nRT
Corrections to describe the behavior of gases are
called equations rather than laws. These equations P + 2 adjusting measured P up to account for
are good for limited ranges but within those ranges interactions
are better than the ideal gas law.
larger a stronger attractions
V – nb adjusting V down to account for the volume
Most corrections account for the finite volume of the
molecules and for the attractive forces between the
larger b larger molecular size
a, b are parameters specific and different for each gas
See figure 5.25 Compare the pressures predicted for 0.8 L of Cl
weighing 17.5g at 273.15 K using (a) the ideal gas
equation and (b) the van der Waals equation.