March 15, 2012
Quiz

1. According to Boyle’s Law, at constant temperature,
pressure and volume are inversely related. As
volume decreases the pressure increases. Explain
WHY this is the case.
2. According to Charles’s Law, at constant pressure,
temperature and volume are directly related. As
temperature increases the volume increases as well.
Explain WHY they are directly related.
3. According to Gay-Lussac’s Law, at constant volume,
pressure and temperature are directly related. As
temperature increases the pressure increases.
Explain WHY.
Today’s Objective

Analyze and solve problems involving
the Combined Gas Law and Dalton’s
Law of Partial Pressures
Combined Gas Law

Combination of each of the three basic
gas laws: Boyle’s, Charles’s and GayLussac’s.
Combined Gas Law Equation:
 P1V1 = P2V2
T1
T2
Combined Gas Law

Example 1
A 2.30 L balloon is taken from the base
of a mountain (15°C and 570mm Hg) to
halfway up the mountain (-15°C and
425mm Hg) How big is the balloon?
Combined Gas Law

Example 2
A sealed metal container (250.0 mL, 1.0
atm, 25°C) is placed in a furnace that is
at 500°C. What will be the final
pressure?
Combined Gas Law

Example 3
A gas at 110 kPa and 30.0°C fills a
flexible container with an initial volume
of 2.00 L. If the temperature is raised to
80.0°C and pressure increased to 440
kPa, what is the new volume?
Dalton’s Law of Partial Pressures

Developed by John Dalton in 1805.
States that the total pressure of a
mixture of gases is equal to the sum of
the partial pressures of the gases.
Partial Pressure: Pressure of each gas
in a mixture.
Dalton’s Law of Partial Pressures

Equation:
Ptotal = PA + PB + PC …
Dalton’s Law of Partial Pressures

Example 1
A sealed container contains Hydrogen
gas with a partial pressure of 80.0 kPa
and Nitrogen with a partial pressure of
30.0 kPa. What is the total pressure in
the container?
Dalton’s Law of Partial Pressures

Example 2
A cylinder contains Helium and Argon.
The total pressure is 5.00 atm. The
partial pressure of Helium is 3.50 atm.
What is the partial pressure of the
Argon?
Dalton’s Law of Partial Pressures

Example 3
A planet is discovered that contains
30.0% CO2 and 70.0% CH4 and has a
total pressure of 60.0 kPa. What is the
partial pressure of each gas in the
atmosphere?
Homework

Combined Gas Law Worksheet
Dalton’s Partial Pressure Worksheet
Both are on the website!