Gas Laws

Pressure vs. Temperature Lab and Pressure vs. Volume Lab and Finding R Lab

  1. Pressure vs. Temperature Lab
    1. Introduction/Background: What is pressure? What is temperature (both Kelvin and celsius scales)? How are pressure and temperature related and why? State Gay-Lussac's law and the purpose of this lab. Anything else of relevance that comes to mind would also fit here.
    2. Hypothesis: Sketch what you think a graph of P vs. T would look like and give your reasoning.
    3. Procedure: Measure various pressures of a sealed container with a pressure gauge at various temperatures.
    4. Data:
       Temperature (°C)  Pressure (psi)
      10.5 26.1
      21.0 26.5
      28.2 26.7
      33.8 27.0
      36.7 27.2
      40.1 27.5
      46.2 27.8
      55.4 28.5
      62.6 29.8
      66.9 30.3
    5. Data Analysis: Graph P (y-axis) vs. T(x-axis). Sketch in your lab book. Do a linear regression. A P-T graph should go through 0,0 (why?) but yours doesn't (because . . ). Find the x-intercept and state its significance.
    6. Evaluation: None
    7. Conclusion: State your x-intercept and the conversion between Kelvin and celsius, in equation form.
  2. Pressure vs. Volume Lab
    1. Introduction/Background: See Pressure vs. Temperature lab above. Apply similar ideas, but to pressure and volume.
    2. Hypothesis: Sketch a graph of what you think P vs. V should look like. Explain.
    3. Procedure:
      1. Obtain a syringe and a 2-liter bottle.
      2. Mass empty bottle. Record.
      3. Measure and record the diameter of the syringe.
      4. Zero syringe with copper wire.
      5. Add 600.0 mL water to the bottle. Balance this on the syringe, record the volume of the syringe. At this point, you are only filling in the first two columns in the data table. The remaining columns are calculations.
      6. Add 100.0 mL more to the bottle. Balance again on the syringe, record the volume of the syringe.
      7. Repeat step 6 until a total of 2000.0 mL are in the bottle.
    4. Data: (remember to add appropriate units, if not given.)

      Mass of Bottle = ________ Diameter of the syringe = ________

      Volume of syringe (mL) Volume of water (mL) Total mass (kg) Weight (N) Pressure (Pascals) Pressure (kPa)
        600.0        
        700.0        

      Continue the data table until 2000.0 mL have been used.

      Calculations:
      Show one sample of each equation, with the original equation clearly shown and one set of numbers only.
      Total mass = mass of bottle + mass of water. (Convert to kg)
      Weight (N) = mass x gravity => W=mg=(total mass in kg)(9.8067 m/s2)
      Pressure (Pa) = Force/area = Weight/(area of syringe, in m2)

    5. Data Analysis:
      1. Graph Volume of syringe (in mL) (y-axis) vs. Pressure (in kPa) (x-axis). Sketch. (No linear regression.) Explain the shape of the curve. Relate to your hypothesis.
      2. To obtain a straight line, 1/V can be graphed vs. Pressure. Do this and find the linear regression of the points. Sketch graph.
      3. The graph should be going through (0,0) (why?). Find the x-intercept, explain why it is not going through the origin, and what the value represents.
    6. Evaluation and Conclusion: as usual, according to the lab format handout.
  3. Finding R
    1. Introduction/Background: As usual, according to the lab format handout. The purpose of this lab is to find the value of R using experimental values.
    2. Hypothesis: Give the value of R with the three different pressure units.
    3. Procedure:
      1. Record the temperature and pressure of the room.
      2. Record the mass of a clean, dry, empty container with the lid.
      3. Fill the container with CO2 gas. Mass and record.
      4. Fill the container completely with water. Put on the lid. Make sure there are no air bubbles in the container. Dry off the outside, mass and record.
      5. Empty and dry the container.
    4. Data: Make up the table as needed to record all the information.
    5. Data Analysis: Remember to show all equations used.
      1. Find the volume of the container by using the mass of the empty container and the mass of the container with water.
      2. The container is not truly empty, it contains air, which affects the mass. The next calculation will find the mass of air. This is done by knowing the volume (found in calculation a), then using the density of air. Unfortunately, the reference value for the density of air is only known at STP and it is 1.29 g/L. Two steps are needed to find the mass of the air.
        1. You know the volume of the air (container), the temperature of the room, and the pressure of the room. Find the volume at STP.
        2. Knowing the volume at STP, use the density at STP to find the mass of the air.
      3. Find the mass of the truly empty container.
      4. Find the mass of just the CO2.
      5. Find R using the original volume, pressure, and temperature. Remember to check units.
    6. Evaluation and Conclusion: as usual, according to the lab format handout.

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