Chemistry
Ms. Boon
Unit 5: Gas Laws: The combined Gas Law and Avogadro’s Law
Name: ____________________________
Period: ______ Date: _______________
Gas Laws Mini-Review
Gay-Lussac’s Law: At constant volume, pressure and temperature are _________________ proportional.
For example, as pressure increases, temperature __________________.
Charles’s Law: At constant pressure, volume and temperature are ________________ proportional. For example, as
volume increases, temperature ____________________.
Boyle’s Law: At constant temperature, volume and pressure are _______________ proportional. For
example, as volume increases, pressure ___________________.
The Combined Gas Law

The combined gas law combines ________________________, _____________________, and ____________________
into one. If you are given any five of the variables, you can solve for the sixth.
Think Box: Why do we need the combined law? What new situation does it address?
Example 1: P1=300 torr, P2=900 torr,
V1=40 L, V2= 10 L, T1=250 K
T2=???
Example 2: A cheetohs bag is sitting in a
car at STP and has a volume of .5 L.
Then, the car is heated to 27 °C. The
pressure increases to 1.2 atm. What is the
bag’s new volume?
Example 3: If a gas at 6 L and 30 torr is
compressed to a pressure of 600 torr, what
is the new volume of gas?
1. P1=500 torr, P2=1000 torr, V1=?? L, V2=
20 L, T1=200 K
T2=100 K
4. A balloon at 200 K is filled with 4 L of
He gas at 2 atmospheres. As the balloon
is flown through colder air at 100 K, it is
compressed to a volume of 1 L. What is
the final pressure?
7. A piston filled with 3 liters of gas at 27
degrees Celsius is compressed down to 1
L. What is the final temperature in
Celsius? What is the final temperature in
Kelvin?
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Chemistry
Ms. Boon
Name: ____________________________
Period: ______ Date: _______________
2. P1=2.0 atm, P2=??, V1=3 L, V2= 30 L,
T1=200 K T2=100 K
5. 2 Liters of a gas at STP is expanded to
4 Liters and 273 K. What is the final
pressure?
8. A balloon at 546 K, 4L, and 2 atm is
cooled down to STP. Find the final
volume.
2. P1=4.0 atm, P2=16.0 atm, V1=3 L, V2=
30 L, T1=100 K T2=??
6. 30 mL of gas at STP is heated to 50
degrees Celcius and the pressure is
changed to 0.5 atm. Now, what is the
volume of the gas?
9. A syringe is filled with 8 L of a gas at
STP. The temperature is maintained at
273 K and volume is compressed to 4 L.
What is the final pressure?
Avogadro’s Law: The relationship between number of molecules and volume



In 1811, Italian scientist Amadeo Avogadro found that equal volumes of all
gases, under the same conditions, have the
_______________________________________________.
Specifically, at standard temperature and pressure,
___________________________________ has a volume of 22.4 L.
Avogadro’s law means that gas volume is ______________________________
to the number of moles of gas at the same temperature and pressure.
Example 1: V1 = 22.4 L, n1 = 1 mol, V2 =
___ , n2 = 5 mol
Example 2: What is the volume of 10 mol
of nitrogen gas at STP?
Example 3: 6 mol of ammonia gas has a
volume of 120 L. At the same temperature
and pressure, what is the volume of 18 mol
of ammonia?
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Chemistry
Ms. Boon
Name: ____________________________
Period: ______ Date: _______________
1. V1 = 30 L, n1 = 2 mol, V2 = ___ , n2 =
6 mol
3. What volume of carbon dioxide contains
the same number of molecules as 20.0 mL
of oxygen at the same conditions?
5. 15 mol of hydrogen gas has a volume
of 300 L. If temperature and pressure are
held constant, how many moles are in 900
L of hydrogen?
2. V1 = 10 L, n1 = 5 mol, V2 = 100 L , n2
= ___ mol
4. A very large balloon holds 224 L of
helium gas at STP. If 5 moles of helium
are released from the balloon, how many
moles of helium remain? What is the new
volume of helium?
6. A 140 mL sample of fluorine gas
contains 0.7 mol fluorine. At constant
temperature and pressure, what is the
volume of 4.9 mol fluorine?
1. Why is it easy to compress a gas?
Mixed Practice
4. If the volume of a gas decreases by a factor of 10,
what will happen to the gas pressure? (Assume
temperature is held constant.)
2. What causes atmospheric pressure?
5. A student blows up a balloon in class. Then, the
balloon is dipped into a container of liquid nitrogen.
Liquid nitrogen has an extremely low temperature.
What happened to the gas particles in the balloon?
3. The atmospheric pressure on top of Mount Everest is
58 kPa. What is this pressure in atmospheres?
6. The volume of air in a tire is 2 L at 1.00 atm and 30
°C. If the temperature decreases to standard
temperature and the pressure remains constant, what
is the new volume?
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