Physlet Illustration: Ideal Gas Law at Constant Volume

 

 

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A piston is clamped in place at the top of a cylinder filled with an ideal gas, fixing the volume at 960 cm3. The cylinder is surrounded by a constant temperature bath. A digital temperature probe, which reads the gas temperature in °C, is attached to the cylinder. A digital pressure sensor, which reads the pressure in kPa, is also attached. Play the animation to heat the temperature bath, and see how the pressure changes. The graph shows pressure (in kPa) vs. temperature (in Kelvins). Can you verify the Ideal Gas Law? How many moles of gas are in the cylinder?

Hints:

  1. What happens to the pressure as the temperature of gas increases?
  2. Pause the animation and determine P and T (in Kelvins) at some instant. Find the ratio P/T.
  3. Pause the animation again and determine P/T. Does this ratio remain constant?
  4. Convert P into Pa (i.e. N/m2), V into m3 and T into Kelvins.
  5. Using PV = nRT, then, can you calculate the number of moles of gas?

Reference

See Walker, Section 17-1

Illustration written by Steve Mellema