Answer:
The change in enthalpy of helium is 4073.86kJ/kg
Step-by-step explanation:
∆H = Cp(T2 - T1)
Cp = 3.5R = 3.5×8.314 = 29.099kJ/kgmolK ÷ 2 (1kgmol of helium = 2kg of helium) = 14.5495kJ/kgK, T2 = 300°C = 300+273K = 573K, T1 = 20°C = 20+273K = 293K
∆H = 14.5495kJ/kgK(573K - 293K) = 14.5495kJ/kgK × 280K = 4073.86kJ/kg