## Constant Pressure of Krypton (4c.3 7th Edition)

Henry Krasner 1C
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### Constant Pressure of Krypton (4c.3 7th Edition)

How are we supposed to calculate the pressure and volume constant of Krypton?
Specifically where does the (5/2) x 8.314 J.mol.K come from for the constant pressure for example?

Chem_Mod
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### Re: Constant Pressure of Krypton (4c.3 7th Edition)

Krypton is a monatomic gas, so assuming it is an ideal gas, its heat capacity at constant volume will be 3 x $\frac{1}{2}$ R.
CP = CV + R for an ideal gas, so CP = $\frac{3}{2}$ R + R = $\frac{5}{2}$ R
R = 8.3145 $\frac{J}{mol K}$

This is because each translational degree of freedom contributes $\frac{1}{2}$ R and each rotational degree of freedom contributes $\frac{1}{2}$ R to CV. Kr has three translational degrees of freedom and no rotational degrees of freedom.