Chemistry v10
Chem Live
Lesson 5.03
Gas Laws
Concept Review: Kinetic Molecular
Theory
Kinetic Molecular Theory makes 5 assumptions that
ideal gases follow to relate pressure, volume, moles
and temperature.
1. Gas particles have kinetic energy.
-The greater the kinetic energy, the faster the movement.
They travel in straight lines, change direction after each
collision.
2. Gas particles occupy a volume 1,000 times greater
than a solid or liquid.
So, there is a lot of empty space between them.
Concept Review: Kinetic Molecular
Theory
3. Gases have elastic collisions - no net gain or loss of
kinetic energy
A sample of gas will have constant average kinetic energy at
constant temperature and volume.
4. Gas particles move so quickly the attractive forces
between them are negligible so it can be ignored
5.The higher the temperature (measured in Kelvin) of a
gas, the greater the average kinetic energy of the
sample.
Concept Review: Physical
Characteristics of Gases
• Gases exert pressure due to the collision of
the particles with the surfaces, such as the
walls of the container
• There are several different units of
pressure:
–
–
–
–
Atmospheres (atm)
Millimeters Mercury (mmHg)
kiloPascals (kPa)
Torr
Concept Review: Pressure
Conversions Practice
785 mm Hg = ? Atm
Step 1: Identify the conversion
Factor that relates the units.
1 atm = 760 mm Hg
Step 2:
785 mmHg 1 atm
=1.03 atm
1
760 mm Hg
You try one!
111 kPa = ? atm
Concept Review: Gas Laws
• To fully describe a gas
we must describe the
Volume, temperature,
Pressure, # of particles.
The relationships between the variables are
simple. If we know 3 of the 4 we can
calculate the other.
Boyle’s Law Practice
Ex. A sample of gas has a volume
of 1.2 liters when its pressure is
0.98 atm. What would be the
resulting volume if the pressure
increased to 1.30 atm while
temperature and moles remained
constant?
Step 1: List variables
P1 = 0.98 atm
V1 = 1.2 L
P2 = 1.30 atm
V2 = ? L
Step 2: Plug In and Solve
V2 = P1V1
P2
V2 = 0.98 atm x 1.2 L
1.30 atm
V2 = 0.90 L
Boyle’s Law Practice
• A gas in a 4.0 L container has a pressure of 3.2 atm. What is the
resulting pressure if the gas is allowed to expand to a volume of
5.8L L?
Charles’ Law
A sealed helium-filled balloon has a
volume of 2.50 liters at 21.5°C. The
volume of the balloon decreases to
2.32 liters after being placed in a
freezer overnight. Based on this
change in volume, what is the
temperature in the freezer?
Gay-Lussac’s Law
An aerosol can filled with gas has a
pressure of 2.95 atm at a
temperature of 25°C. The warning
on the can says to not allow the
temperature to exceed 50°C. What
would be the pressure of the gas
inside the aerosol can at a
temperature of 50°C, assuming
volume and moles remained
constant?
Avogadro’s Law
A balloon containing 0.85 moles of
gas occupies a volume of 2.3 liters. If
0.50 moles of gas are added to the
balloon, giving a total of 1.35 moles of
gas, at a constant temperature and
pressure, what is the resulting volume
of the balloon?
Ideal Gas Law
• A single gas law developed to combine all 4
variables into one equation
PV = nRT
R, represents a constant known as the ideal gas
constant. Its value depends on the units used
for pressure, volume, moles, and temperature.
Ideal Gas Law Practice
• What is the volume, in liters, occupied by 0.485 moles of
oxygen gas (O2) at 23.0°C and 0.980 atm?
Step 1: List variables
P= 0.980 atm
V=?
n=0.485 moles
R = 0.0821 L atm/mol K
T = 23.0 C + 273 = 296 K
Step 2: Solve Equation for
desired variable.
V = nRT/ P
Step 3: Plug in & Solve
V = 0.485 x 0.0821 x 296
0.980
V = 12.0 L
Ideal Gas Law Practice
• How many moles of chlorine gas (Cl2) are contained in an
8.5 liter tank at 298 K and 3.20 atm?
Ideal Gas Law Practice
• What would be the pressure, in atmospheres, of 4.3
moles of gas in a 1.43 liter tank at 285 K?
Chemistry v10
Chem Live
Lesson 5.03
Gas Laws Lab
Part 1: Boyle’s Law Lab
Data and Observations:
1) Record your data for volume and pressure below.
2) Include an observations section for any observations that
you made during the lab.
Part 1: Boyle’s Law
Graph:
Create a graph of your data for this part of the lab. You may use any graphing tool to create
the graph, but be sure to follow common guidelines for creating a graph. (5 points)
1) Pressure should be in Kilo pascals( KPa) and volume in Milliliters (mL).
2) Place Pressure on the Y-axis and volume on the X-axis.
3) Use the link below to create and paste your graph in your worksheet:
http://nces.ed.gov/nceskids/createagraph/default.aspx
Part 1: Boyle’s Law
Conclusion:
Answer the following questions after completing the lab.
1. Describe the relationship that you observed between pressure and volume in
this lab. Refer to your data and/or graph to help support your answer. (3
points) Is the relationship on this graph direct or is it inverse?
As ________________increases, ___________________ decreases.
2. Do you think there is a point at which volume cannot be decreased anymore
for this sealed container of gas? Explain your answer in terms of what you
know about the properties and characteristics of gases. (3 points)
Think about the motion and volume of the particles at the given temperature.
Part 2: Charles’s Law
Part 2: Charles’s Law Lab
1)
Record your data for temperature and volume
2) Include an observations section for any observations that you made during the
lab.
Part 2: Charles’s Law
Graph:
Create a graph of your data for this part of the lab. You may use any graphing tool to create the
graph, but be sure to follow common guidelines for creating a graph. Be sure to graph
temperature in the unit Kelvin and volume in the unit Liters. (5 points)
1) Temperature should be in Degrees Celsius( C ) and volume in Milliliters (mL).
2) Place Temperature on the Y-axis and volume on the X-axis.
3) Use the link below to create and paste your graph in your worksheet:
http://nces.ed.gov/nceskids/createagraph/default.aspx
Part 2: Charles’s Law
Conclusion:
1. Describe the relationship between volume and temperature,
referring to your data and/or graph to support your answer. (3
points) Volume and temperature are_______________(
inversely/directly) related, as one ___________the other
_____________________.
2. Do you think there is a point at which volume cannot be decreased
any further for this sealed container of gas? Explain your answer in
terms of what you know about the properties and characteristics of
gases.