# Entropy and the partition function for nitrogen

• jbowers9
Anyway, thanks for the pointer.In summary, the translational entropy for nitrogen gas is 207.8 j/kgmol. The tabulated value is 150.4, but the discrepancy may involve a factor of .01 or .001.f

## Homework Statement

I'm attempting to calculate the translational entropy for N2 and I get a value of 207.8 J/Kmol. The tabulated value is given as 150.4 and I am stumped as to why the decrepancy.
T = 298.15 K and P = 0.99 atm and V = 24.8 L
R = 8.314 J/Kmol[/B]

## Homework Equations

Strans = R ln[(2ΠmkT/h2)3/2*V*e5/2/Na][/B]

## The Attempt at a Solution

I plugged in all the correct(?) values and cannot figure out what I'm doing wrong.
[/B]

Last edited:
What value did you use for the mass?

28 amu =
4.65E-26 kg

My calculated value is off by 30% which is huge. I rechecked the constants I used and the units :
h = 6.63E-34 m2kg/s
k
B = 1.38E-23 JK-1
NA
= 6.02E+23
T
= 298.15 K
V
= 24.79 L
I really am stumped. I'm using Excel to do the calculation and I've checked it several times and
ln[(2ΠmkT/h2)3/2*Ve5/2/Na] calculates to 25 when it "should" be about 18 and change.
I don't know where to go with this. All the other entropy contributions to the entropy from the total partition function were right on the mark except this one. HELP!

My calculated value is off by 30% which is huge. I rechecked the constants I used and the units :
h = 6.63E-34 m2kg/s
k
B = 1.38E-23 JK-1
NA
= 6.02E+23
T
= 298.15 K
V
= 24.79 L
I really am stumped. I'm using Excel to do the calculation and I've checked it several times and
ln[(2ΠmkT/h2)3/2*Ve5/2/Na] calculates to 25 when it "should" be about 18 and change.
I don't know where to go with this. All the other entropy contributions to the entropy from the total partition function were right on the mark except this one. HELP!

I've also found, thanks to Excel, that the descrepancy involes either a factor of .01 inside the power expression
(2ΠmkT/h2)3/2 or .001 times the expression [(2ΠmkT/h2)3/2*Ve5/2/Na] but I still don't know what it could be.

Be sure to convert liters to SI units.

• DrClaude
Wow. Thanks a pile dude(?). What an embarassing oversite on my part! (Homer Simpson Duh!) All this time, I'm in my 50's, and I'm thinking liter is, or absentmindedly thinking it is, the SI unit for volume. It's all about the units, man.