[diablo]

Hi folks,

i've got a problem with calculating this:

1mol CO with T₁= 320K and V₁ = 80l
                   changes to T₂= 650K and V₂= 120l

Calculate dS, given the following data:

C_V,m= (31,08-0,01452T/K+3,1415*10^-5T²/K²-1,4973*10^-8T³/K³)JK^-1mol^-1

Solution is: dS = 24,42 JK^-1

Ok, this is my calculation:

dS= dS_start+C_pln(T₂/T₁)

C_p= C_V,m+n.R

dS_start= nRln(V₁/V₂)

if i integrate C_V,m over 650-320K, i get a value of 9836JK^-1mol^-1
(with C_{V,m, 650K} = 19342,23 and C_{V,m 320K}= 9506)

now im really confused, and i can't find the error

plz help

[vhpk]

Ok, I haven't tried yet, but I think the process could be as follows:
The change is in both volume and pressure, hence you applied the formula:
 :delta:S = nRln(T2/T1) + nCpln(V2/V1)
However, maybe the fault is at the back of your formla, when the volume is changed, the differential expression should be like this:
dS = CpdT/T
Then you take the integration to get the answer.
So now I think you can try it and get the answer
Btw, the "," sign means decimal or are you confused with "." sign ?