Answer:
The lectures in this unit cover gases. This lecture covers the Ideal Gas Law and partial pressures.
Ideal Gas Law
In our previous lecture we discovered a relationship between the pressure, volume, temperature,
and number of moles in gases. After scientists worked out the individual relationships between
pressure, volume, temperature, and the number of moles, it was clear that a single law could
bring all of these individual laws together. This unifying law is called the ideal gas law. An
ideal gas is one which follows the ideal gas law. Not all gases are perfectly ideal in this sense
but most of them are close enough to it that the law applies well.
I. Ideal Gas Law
The Ideal Gas Law unifies all these independent laws as follows:
PV = nRT
Where P = Pressure, V = Volume, T = Temperature, and n = number of moles.
The remaining value, R, is the constant which makes the rest of these factors work together
mathematically. Once the relationship between all individual factors was found it was trivial to
calculate R: it is the value of
PV
nT for any gas since they all act the same way!
There are several numerical values for R depending on which units you are using (atm or torr or
bars, L or mL, Joules (energy) etc). Our class uses this one:
R = .0821
L·atm
mole·K
The ideal gas law helps us calculate variables such as pressure, volume, temperature, or number
of moles without having to make a comparison.
For example, if 3.5 moles O2 has a volume of 27.0 L at a pressure of 1.6 atm, what is the
temperature of the sample?
Here we are given n = 3.5 moles, V = 27.0 L, P = 1.6 atm. We rearrange the ideal gas law to
solve for temperature as follows:
PV = nRT
PV
nR = T
(1.6 atm)(27.0 L)
(3.5 moles)(0.0821 L·atm/mol·K) = 150.3 K
Explanation:
