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JoVE Lab Manual
Lab: Chemistry
Education
Ideal Gas Law
 

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Learning Objectives

At the end of this lab, students should know...

What is a gas?

A gas is a fundamental state of matter that is a collection of molecules with significant distance between them. Gases are highly compressible and are the least dense state of matter.

What is the relationship between pressure, volume, number of moles, and temperature?

Pressure and volume are inversely proportional to each other, volume and temperature are proportional to each other, pressure and temperature are proportional to each other, and the number of moles and volume are proportional to each other.

What four parameters are related by the ideal gas law?

The ideal gas law relates pressure, volume, number of moles, and temperature using the ideal gas constant.

What gases are described by the van der Waals modified gas law?

The van der Waals modified gas law takes into account molecular size, intermolecular forces, and volume to define real gases that deviate from ideal behavior.

What are the assumptions of the Ideal Gas Law?

The ideal gas law assumes the following: (1) the collisions between molecules are elastic and their motion is frictionless, (2) the total volume of the gas molecules is orders of magnitudes smaller than the volume occupied by the gas, (3) there are no intermolecular forces acting between the molecules or their surroundings, and (4) the molecules are constantly in motion, and the distance between two molecules is significantly larger than the size of individual molecules.

List of Materials

  • Dumas tube
    5
  • 500-mL glass Erlenmeyer flask
    5
  • 500-mL glass filter (Büchner) flask
    5
  • 400-mL glass beaker
    5
  • 150-mL glass beaker
    5
  • 100-mL glass beaker
    5
  • Thermometer
    5
  • Neoprene single-hole rubber stopper (size 4)
    5
  • 20-mL plastic syringe
    5
  • 6" reusable, non-sterile needle
    5
  • Bunsen burner
    6
  • Test tube holder
    5
  • Fire striker
    5
  • Lab stand
    5
  • Ring fixture
    5
  • Large 3-prong clamp
    5
  • Thermometer clamp
    5
  • 18" length of latex tubing
    10
  • 18" length of silicone tubing
    5
  • Square of wire gauze
    5
  • 1,2-dichloroethane
    20 mL
  • Trichloroethylene
    20 mL
  • 2-bromopropane
    20 mL
  • Acetone
    20 mL
  • Barometer
    1
  • 50-mL brown glass bottle with cap
    3
  • 50-mL clear glass bottle with cap
    1
  • 22-G 6" non-sterile, stainless-steel needle
    4
  • 5-mL glass syringe
    4
  • 25-mL glass beaker
    4
  • Watch glass
    4
  • 20-mL volumetric pipette
    4
  • Volumetric pipetter
    4
  • Analytical balance (at least 1)
    Dependent on lab size
  • 250-mL plastic beaker
    Dependent on lab size
  • Boiling chips
    Dependent on lab size
  • Paper towels
    Dependent on lab size
  • Laboratory wipes
    Dependent on lab size

Lab Prep

Source: Smaa Koraym at Johns Hopkins University, MD, USA

  1. Preparation of the Laboratory

    Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.

    • Put on a lab coat, splash-proof safety glasses or goggles, and appropriate gloves for the chemicals you will be handling.
    • The day before the lab, place the Dumas tubes in an oven at 125 °C.
    • Two hours before the lab, remove the tubes from the oven and place them on a heat-resistant surface to cool. Distribute the tubes to each workstation once they have reached room temperature.
    • Place a barometer in an easily accessible location.
    • Set a plastic 250-mL beaker next to each analytical balance, and ensure that a box of laboratory wipes is available for each balance.
    • Set up a Bunsen burner in a fume hood, and place a striker and a test tube holder with the burner.
    • Set out the following glassware and equipment at each workstation (we suggest students work in pairs):
       1    500-mL Erlenmeyer flask
       1    500-mL Büchner flask
       1    400-mL beaker
       1    100-mL beaker
       1    Lab stand
       1    3-prong clamp
       1    Ring fixture with square of wire gauze
       1    Bunsen burner and fire striker
       2    18-in length of latex tubing
       1    18-in length of silicone tubing
       1    Thermometer and thermometer clamp
       1    Single-hole #4 rubber stopper
  2. Preparation and Dispensing of Unknown Liquids
    • Label one 50-mL glass bottle and one 20-mL glass syringe as 'deionized water'.
    • Label three 50-mL brown glass bottles, three 5-mL glass syringes, and three 25-mL glass beakers as ‘1’ through ‘3’, and set them in a reserved fume hood.
    • Place a watch glass and 20-mL volumetric pipette next to each numbered bottle along with a pipetter. Set four 22-gauge, 6-in needles next to each syringe.
    • Group the glassware by label in a reserved fume hood according to their chemical compound: 1,2-dichloroethane, trichloroethylene, and 2-bromopropane.
    • Transfer at least 20 mL of each organohalide into its assigned bottle using a volumetric pipette: 1,2-dichloroethane in bottle 1, trichloroethylene in bottle 2, and 2-bromopropane in bottle 3. Cap each bottle once the liquid has been added.
    • Label a fifth 50-mL bottle, 5-mL glass syringe, and 25-mL beaker as 'acetone', and set a 22-gauge, 6-in needle next to the syringe.
    • Add about 20 mL of acetone in the appropriately labeled bottle and cap it.
    • When it is time to dispense the unknown liquids during the laboratory, pour at least 5 mL of an unknown into the matching beaker. Submerge the tip of the matching syringe in the unknown and slowly withdraw the plunger to fill the syringe to the 5-mL mark. Connect the needle and set down the syringe on a weight paper. Cover the beaker with a watch glass after filling.
    • Repeat this process for each organohalide.
    • Call up each student group one by one. Insert the needle of the syringe with their assigned unknown liquid into the long neck of the Dumas tube and dispense 0.5 mL. Withdraw the needle, taking care to avoid letting the liquid drip on the outside of the tube. The student group can now begin their trial.
    • Dispense the unknowns for the rest of the lab in this way, refilling the syringes as needed. At the end of the lab, follow the same procedure to dispense 0.5 to 1 mL of acetone into each tube for cleaning by students. The amount of acetone will depend on the amount of water left over in the tube.
    • If students need to re-weigh their empty Dumas tube in the middle of the experiment, you will flame dry the tube so that they can obtain an accurate measurement.
    • Light a Bunsen burner and hold the Dumas tube with a test tube holder, and pass the tube through the flame until it appears dry. Note: Three of the organohalides are flammable, so keep the opening of the tube away from the flame.
    • Then, hold the tube away from the flame for 1 min to allow any remaining vapor to condense. If you see liquid at the bottom of the tube after that, pass the tube through the flame again until it appears dry. Once no liquid condenses in the tube after one minute out of the flame, return the tube to the student group so that they can measure the mass.

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