Wie rechne ich... eine isotherme Zustandsänderung?

clear all;
k_B = 1.38064852e10-23
k_B = 1.3806e+10
R = 8.3144598
R = 8.3145
pStd = 1013.25e2
pStd = 101325
TRaum = 293
TRaum = 293
V1 = 1 %l
V1 = 1
h = 2e3
h = 2000
p2 = 850e2
p2 = 85000

V2 = pStd / p2 * V1
V2 = 1.1921