Transcript Gas Laws

Gas Laws
Chapter 11 – Section 3 – Physical
Characteristics of Gases
Boyle’s Law
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Named after Robert Boyle
As pressure increases, volume decreases
As pressure decreases, volume increases
P1V1=P2V2
Only holds true if temperature remains constant
Pressures have to be measured in the same units
Volumes have to be measured in the same units
Practice Problem
• A balloon filled with helium gas has a volume
of 500 mL at a pressure of 1 atm. The balloon
is released and reaches an altitude of 6.5 km,
where the pressure is 0.5 atm. Assuming that
the temperature has remained the same,
what volume does the gas occupy at this
height?
• P1V1=P2V2
Your turn!
• A gas has a pressure of 1.26 atm and occupies
a volume of 7.40 L. If the gas is compressed to
a volume of 2.93 L, what will its pressure be,
assuming constant temperature?
Charles’s Law
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Named after Jacques Charles
As temperature increases, volume increases
As temperature decreases, volume decreases
V1 = V2
T1 T2
• Only holds true if pressure remains constant.
• Volumes must be in the same unit.
• Temperature must be measured in Kelvin.
A practice problem
• A helium-filled balloon has a volume of 2.75 L
at 20⁰C. The volume of the balloon decreases
to 2.46 L after it is placed outside on a cold
day. What is the outside temperature?
Your turn!
• A gas at 65⁰C occupies 4.22 L. At what Celsius
temperature will the volume be 3.87 L,
assuming the same pressure?
Gay-Lussac’s Law
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Named after Joseph Gay-Lussac
As temperature increases, pressure increases
As temperature decreases, pressure decreases
P1 = P2
T1 T2
• Only holds true if volume remains constant
• Pressures must be measured in the same units
• Temperatures must be in Kelvin
A practice problem
• Before a trip to New York to Boston, the
pressure in an automobile tire is 1.8 atm at
20.0C. At the end of the trip, the pressure
gauge reads 1.9 atm. What is the new
Celsius temperature of the air inside the
tire? (Assume tires with constant volume.)
Your turn!
• At 120.0C, the pressure of a sample of
nitrogen is 1.07 atm. What will the pressure
be at 2050C, assuming constant volume?