Chemistry v10

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Chemistry v10

• Chem Live
• Lesson 5.03
• Gas Laws

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Concept Review Kinetic Molecular Theory

• Kinetic Molecular Theory makes 5 assumptions that
  ideal gases follow to relate pressure, volume,
  moles and temperature.
• 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.

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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.

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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

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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
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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.

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Boyles 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 2 Plug In and Solve V2 P1V1 P2 V2
0.98 atm x 1.2 L 1.30 atm V2 0.90 L

• Step 1 List variables
• P1 0.98 atm
• V1 1.2 L
• P2 1.30 atm
• V2 ? L

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Boyles 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?

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Charles Law
A sealed helium-filled balloon has a volume of
2.50 liters at 21.5C. 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?
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Gay-Lussacs Law
An aerosol can filled with gas has a pressure of
2.95 atm at a temperature of 25C. The warning on
the can says to not allow the temperature to
exceed 50C. What would be the pressure of the
gas inside the aerosol can at a temperature of
50C, assuming volume and moles remained
constant?
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Avogadros 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?
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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.

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Ideal Gas Law Practice

• What is the volume, in liters, occupied by 0.485
  moles of oxygen gas (O2) at 23.0C and 0.980 atm?
• Step 1 List variables
• P 0.980 atm
• V?
• n0.485 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
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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?

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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?

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Chemistry v10

• Chem Live
• Lesson 5.03
• Gas Laws Lab

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Part 1 Boyles Law Lab
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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.
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Part 1 Boyles 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/nceskid
  s/createagraph/default.aspx

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Part 1 Boyles 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.

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Part 2 Charless Law
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Part 2 Charless Law Lab

• Record your data for temperature and volume
• 2) Include an observations section for any
  observations that you made during the lab.

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Part 2 Charless 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.a
  spx

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Part 2 Charless Law

• Conclusion
• 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.