An ideal gas is heated from 500 to 1500 K. Find the change in enthalpy using constant specific heat from Table A.5 (room temperature value) and discuss the accuracy of the result if the gas is
a. Argon
b. Oxygen
c. Carbon dioxide
TABLE A.5
Properties of Various Ideal Gases at 25°C, 100 kPa* (SI Units)
Gas 
ChemicalFormula 
Molecular Mass(kg/kmol) 
R(kJ/kgK) 
ρ (kg/m3) 
Cp0(kJ/kgK) 
Cv0(kJ/kgK) 

Steam 
H2O 
18.015 
0.4615 
0.0231 
1.872 
1.410 
1.327 
Acetylene 
C2H2 
26.038 
0.3193 
1.05 
1.699 
1.380 
1.231 
Air 
— 
28.97 
0.287 
1.169 
1.004 
0.717 
1.400 
Ammonia 
NH3 
17.031 
0.4882 
0.694 
2.130 
1.642 
1.297 
Argon 
Ar 
39.948 
0.2081 
1.613 
0.520 
0.312 
1.667 
Butane 
C4H10 
58.124 
0.1430 
2.407 
1.716 
1.573 
1.091 
Carton dioxide 
CO2 
44.01 
0.1889 
1.775 
0.842 
0.653 
1.289 
Carton monoxide 
CO 
28.01 
0.2968 
1.13 
1.041 
0.744 
1.399 
Ethane 
C2H6 
30.07 
0.2765 
1.222 
1.766 
1.490 
1.186 
Ethanol 
C2H5OH 
46.069 
Solution 127HP
Part (a)
Step 1 of 7:
Our aim is to find the change in enthalpy of the Argon (ideal gas condition) and to discuss the accuracy of the change in enthalpy.
The initial temperature T1 = 500 K
The final temperature T2 = 1500 K
The heat capacity of Argon Cp0 = 0.52 kJ/kg.K
The change in temperature ΔT = T2  T1 = 1000 K
Step 2 of 7:
The change in enthalpy is expressed as
Putting the Values
The change in the enthalpy of Argon is 520 kJ/kg.
The equation for specific heat is given by (Table A.6)
Where C0 = 0.52 kJ/kg.K and rest of the values (C0  C3) are zero for argon. The change in enthalpy matches with the standard value as the equation given in the table A.6 does not affect the specific heat value.
Part (b)
Step 3 of 7:
Our aim is to find the change in enthalpy of the Oxygen and to discuss the accuracy of the change in enthalpy.
The initial temperature T1 = 500 K
The final temperature T2 = 1500 K
The heat capacity of Oxygen Cp0 = 0.992 kJ/kg.K
The change in temperature ΔT = T2  T1 = 1000 K
Step 4 of 7:
The change in enthalpy is expressed as
Putting the Values
The change in the enthalpy of Oxygen is 992 kJ/kg.