Unit 9: Gases
Ideal Gas Law
After today you will be able to…
• Explain what an ideal gas is
• Calculate an unknown pressure,
temperature, volume, or amount
of gas using the ideal gas law
equation
Ideal Gases
•Ideal gases are gases that are
said to follow all assumptions
of kinetic molecular theory.
•An ideal gas is also considered
to conform to all gas laws.
Ideal Gases
•Up until now we have only changed
variables such as pressure, volume, and
temperature of a gas.
•In each of these cases the amount of
gas was assumed constant.
•The combined gas law can be modified
to include the amount of gas by
including the variable, n.
Ideal Gas Law
This gas law relates the
amount of gas (in moles) to
the volume it would occupy
at a particular temperature
and pressure.
Ideal Gas Law
STOP!
It
is
PV=nRT
Where,
often
called
P= pressure
(atm)
V= volume (L)
the “picky” law!
n= moles (mol)
The
units must be
R= 0.0821
L·atm/mol·K
T= temperature
(K) see here!
what you
R is called the Ideal Gas Constant
(it has multiple values, but for our
purposes we will only use this one).
Ideal Gas Law Example
At what pressure would 0.212 mol of a gas occupy
6.84L at 89°C?
PV=nRT
P= ?
(P)(6.84L)=(0.212mol)(0.0821)(362K)
V= 6.84L
P = 0.92atm
n= 0.212mol
R= 0.0821L·atm/mol·K
T= 89°C + 273= 362K
Ideal Gas Law Example
At what temperature would 52.3g of methane
(CH4) gas occupy 65.7L at 184kPa?
PV=nRT
P= 184kPa x 1 atm =1.82 atm
101.3kPa
V= 65.7L
1 mol CH4
52.3gCH
x
n=
= 3.26 mol CH4
4
16.05gCH4
R=0.0821L·atm/mol·K
(1.82atm)(65.7L)= (3.26mol)(0.0821) (T)
T= ?
T = 447K