One compartment of an insulated rigid tank contains 3 kmol of CO₂ at 20°C and 140 kPa while the other compartment contains 5 kmol of H₂ gas at 35°C and 280 kPa. Now the partition between the two gases is removed, and the two gases form a homogeneous ideal gas mixture. The temperature of the mixture is

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N_H2=5 "kmol"
T1_H2=35 "C"
P1_H2=280 "kPa"
N_CO2=3 "kmol"
T1_CO2=20 "C"
P1_CO2=140 "kPa"
Cv_H2=10.183; Cp_H2=14.307 "kJ/kg.K"
Cv_CO2=0.657; Cp_CO2=0.846 "kJ/kg.K"
MM_H2=2 "kg/kmol"
MM_CO2=44 "kg/kmol"
m_H2=N_H2*MM_H2
m_CO2=N_CO2*MM_CO2
"Applying Energy balance gives 0=DeltaU=DeltaU_H2+DeltaU_CO2"
0=m_H2*Cv_H2*(T2-T1_H2)+m_CO2*Cv_CO2*(T2-T1_CO2)
"Some Wrong Solutions with Common Mistakes:"
0=m_H2*Cp_H2*(W1_T2-T1_H2)+m_CO2*Cp_CO2*(W1_T2-T1_CO2) "Using Cp instead of Cv"
0=N_H2*Cv_H2*(W2_T2-T1_H2)+N_CO2*Cv_CO2*(W2_T2-T1_CO2) "Using N instead of mass"
W3_T2 = (T1_H2+T1_CO2)/2 "Assuming averate temperature"

One Compartment of an Insulated Rigid Tank Contains 3 Kmol