HONORS CHEMISTRY
May 6, 2014
Brain Teaser
• Rationalize the following observations.
– A thin-walled can will collapse when the air inside is
removed by a vacuum pump.
– Aerosol cans will explode if heated
Agenda
• Brain Teaser
• Notes: Combined Gas law, Avogadro’s Law
and Ideal Gas Law
• Homework
– Combined Gas Law Worksheet
• Questions 2,4,6,8
– Ideal Gas Law Worksheet
• Questions 1,2,4,6
Combined Gas Law
Boyle’s Law
Charles’s
Combined
P1V1  P2V2
V1 V2

T1 T2
P1V1 P2V2

T1
T2
Avogadro’s Law
• How can we change the volume of a gas in a
balloon?
Avogadro’s Law
• Why did the blimp deflate?
Avogadro’s Law
• If the pressure and temperature are held constant,
the
V volume
 m(n)of
 ba gas is directly proportional to the
number of moles (n).
b0
V
m
n
V1 V2

n1 n2
V
n
Gas Laws Part 2: Work on Gas Notes Sheet
instead of Brain Teaser
Avogadro’s Law
O2  O 3
Suppose we have a 12.2 L sample containing 0.50 mol
oxygen gas at a pressure of 1 atm and a temperature of
25 ºC.
1) Balance the equation
2) If all this oxygen is converted to ozone at the same
temperature and pressure, what would be the volume
of the ozone?
• The total
pressure is the
sum of the
partial pressures.
• Ptotal = P1 + P2 +
P3 + …..
Dalton’s Law Practice
• A mixture of oxygen, carbon dioxide, and
nitrogen has a total pressure of 0.97atm.
What is the partial pressure of Oxygen, if the
partial pressure of carbon dioxide is 0.70atm
and the partial pressure of nitrogen is
0.12atm?
The Gas Laws
• Variables: V, P, T, n (or m and MM or d)
• Ideal Gas: properties are independent of the
identity of the gas
• What is the relationship between the variables for
an ideal gas?
Basketball
Bike Tire
5.3 Ideal Gas Law
•
•
•
•
•
PV = nRT
P= pressure (atm)
V = volume (L)
n = number of moles
R = ideal gas constant
– 0.08206 L·atm/mol·K
• T = temperature (K)
STP
• Standard Temperature and Pressure
– 0ºC and 1 atm
• Use the Ideal Gas Law to calculate the volume
of 1.00 mol of gas at STP
Molar Volume at STP
• We can show that 22.414 L of any gas at
0C and 1 atm contain 6.02  1023 gas
molecules.
Example
• A sample of Hydrogen gas has a volume of
8.56 L at 0ºC and a pressure of 1.5 atm.
Calculate the moles H2 molecules present
in this gas sample.
Practice Problem
• The volume of an oxygen cylinder is 1.85 L.
What mass of oxygen gas remains in the
cylinder when it is “empty” if the pressure
is 755 torr and the temperature is 18.1oC?
• Answer: 2.46 g