Enthalpy change in solids and gases Calculate the change in

Enthalpy change in solids and gases: Calculate the change in enthalpy of 50 kg of aluminum as it is heated from 300 K to 600 K. What mass of air, heated from 300 K to 600 K does it take to reach that same change in enthalpy?

Solution

m_Al = 50 kg,

C_Al= 0.91 kJ/kg K

T_Al1= 300 K

T_Al2=600 K

T_a1 = 300 K

T_a2 = 600 K

C_a =1.005 kJ/kg K assumed.

Change in Enthalpy of Aluminium, H₂ - H₁ = m_Al*CAl* (T_Al2-T_Al1)

50*0.91*(600-300) = 13,650 kJ.

Let m_a = mass of air required

m_a*C_a* (T_a2-T_a1) =13,650 kJ

m_a = 13,650/1.005*(600-300) = 45.27 kg