Answer to Question #266170 in Molecular Physics | Thermodynamics for Neilmar

Question

Assume 2 kg of hydrogen (Item B 28) are initially at 40 atm, 100 K. (a) If the hydrogen changes pressure to 1 atm without a change of temperature, find the changes of enthalpy and entropy. (b) If the hydrogen changes temperature to 35 K with no change of entropy, find the change of pressure and enthalpy.

Answer 1

a)

$H=\nu c_pT=271 \frac JK,$

$S=\frac{\nu p}{c_pT}=56~\frac JK,$

b)

$p=\frac{\nu (T_2-T_1)}{c_p}=38~Pa,$

$H=\nu pT=71~\frac JK.$