Calculating Heat Capacity of Krypton at 90K

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The discussion centers on calculating the heat capacity of krypton atoms adsorbed on a surface at 90K, treating them as a two-dimensional gas due to their confinement. Participants clarify that the surface density and area can be used to determine the number of moles of krypton by multiplying the surface area by the surface density. The degrees of freedom for this 2D gas is two, impacting the calculation of internal energy and specific heat. The specific heat at constant volume for this system simplifies to the gas constant R, as derived from the internal energy equations. The conversation emphasizes the distinction between 2D and 3D gas behavior, particularly in terms of energy distribution and specific heat calculations.
  • #31
davedavidson said:
Sorry if I’ve missed something but why are you using specific heat at constant volume? The volume isn't constant; the question states that the gas is free to move along the surface. Wouldn’t it be c at constant pressure?

Well, the surface area is of a fixed size. The atoms are constrained to that fixed-size surface. It's the 2D equivalent to the 3D constant volume case.

I suppose that, notationally, the constant should be CA, for constant area!
 
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  • #32
davedavidson said:
Sorry if I’ve missed something but why are you using specific heat at constant volume? The volume isn't constant; the question states that the gas is free to move along the surface. Wouldn’t it be c at constant pressure?

The problem states that the atoms of the 2D gas are free to move on the surface.

The particles of a normal gas in 3 dimension move freely inside the container. The volume of the gas is defined as the volume of the container.

The particles of the 2D gas move freely on a certain surface. The area of the surface plays the role of volume.


ehild
 

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