Thermodynamics: Internal Energy and Enthelpy

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SUMMARY

The discussion clarifies the relationship between enthalpy (H) and internal energy (U) in the context of thermodynamics, specifically for monoatomic ideal gases. It establishes that H is defined as H = U + pV, and for ideal gases, this can be expressed as H = U + nRT. The derivation shows that H is a function of temperature (T) alone, leading to the conclusion that H = H(T) when considering the extensive nature of enthalpy. The intensive quantity h is defined as h = H/n, simplifying the analysis of enthalpy's dependence on the number of moles.

PREREQUISITES
  • Understanding of thermodynamic concepts, specifically enthalpy and internal energy.
  • Familiarity with the ideal gas law, particularly the equation pV = nRT.
  • Knowledge of monoatomic ideal gas properties, including U = (3/2)PV.
  • Basic grasp of extensive and intensive properties in thermodynamics.
NEXT STEPS
  • Study the derivation of enthalpy for different types of gases, including diatomic and polyatomic gases.
  • Explore the implications of the first law of thermodynamics on internal energy and enthalpy.
  • Learn about the application of enthalpy in real-world thermodynamic processes, such as chemical reactions.
  • Investigate the concept of specific enthalpy and its relevance in engineering applications.
USEFUL FOR

Students of thermodynamics, chemical engineers, and anyone involved in the study of gas properties and energy transformations in physical systems.

leah3000
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H = U+ pV
pV = nRT

H= U+ nRT

H= H (T)

I don't understand the transition from U+ nRT to H (T)

Can someone explain this?

I get that H = U + pV

But how is H= U+ nR
 
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For a monoatomic ideal gas, U=(3/2) PV. Hence, H=(5/2) PV=(5/2) nRT
Which shows that H for an ideal gas is a function of T alone ,i.e, H=H(T).
Of course it is also function of n since it is extensive quantity. However, this dependence is easy to get rid of by defining h=H/n which is an intensive quantity.
 
thank you...that clears it up!
 

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