Ideal Gas Law Lab

1
Ideal Gas Law Lab

• PV nRT

2
Pressure Inside Bottle (P2)

• P1 (atmospheric pressure in room, in atm.)
• (divide given atmospheric pressure by
  one of the following 760 Torr, 29.92 in Hg,
  101.3 kPa,
• 1013 millibars)
• P1 V1 P2 V2 P2 P1V1 / V2
• P2 (your answer)
• P1 (atm. pressure in atm)
• V1 (10 mL)
• V2 (volume of air in syringe, in mL)

3
Mass of Air in Bottle (m)

• m (PVM) / RT
• m mass of the air in bottle (your answer, in
  grams)
• P2 atmospheric pressure in atm
• V volume of bottle (minus syringe) in L 1.03
  L
• M average molar mass of air (29.0 g/mol)
• R ideal gas constant (0.0821 Latm/Kmol)
• T room temp. in Kelvin

4
Mass of Bottle/Syringe

• Subtract the mass of air in the bottle from the
  mass of the bottle/syringe plus air for each
  trial.

5
Moles of Air in Bottle (n)

• n mass of air in bottle (g)
• ----------------------------------
• 29.0 g/mol

6
Pressure to Moles Ratio

• Calculate the ratio of pressure inside the bottle
  (P2) to the moles of air (n) in the bottle.
• Find the average of the P/n ratio.

7
Plot Pressure vs Moles

• Sketch graph the pressure inside the bottle
  (Y-axis) as a function of the number of moles of
  air (X-axis).
• Use your graphing calculator to find the slope
  (remember that L1 X-axis and L2 Y-axis).
• How does your slope compare to the P/n ratio?

8
Theoretical Pressure to Moles Ratio

• Theoretical P/n RT/V
• where R ideal gas constant
• T room temperature in Kelvin
• V volume of bottle (in
  liters)
• How does the slope of your graph compare with the
  theoretical pressure to mole ratio? Explain.
• How did the temperature change when the bottles
  was first filled with air and then, when the
  pressure was released? Account for these changes.

9
Error

• What are possible sources for error in this
  experiment?