Enthalpy derivation differential equation

In summary, the derivation of the enthalpy differential equation involves exploring the relationship between enthalpy (H), internal energy (U), pressure (P), and volume (V). The equation is expressed as dH = dU + PdV + VdP, where dH represents the differential change in enthalpy. This derivation considers the first law of thermodynamics, incorporating the effects of heat transfer and work done on or by a system. The equation is essential for understanding thermodynamic processes and systems, particularly in relation to energy changes during phase transitions and chemical reactions.
  • #1
Mardonio
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Homework Statement
A state equation for a certain gas is ##(P + b)v = RT## and its internal energy is ##u = aT +bv +u_o##

show that $$(\frac {\partial H} {\partial v})_P = \frac {C_p T} {v}$$
Relevant Equations
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Good evening,
unfortunately I'm pretty lost in this problem.

I tried to use the chain rule $$(\frac {\partial H} {\partial v})_P = (\frac {\partial H} {\partial T})_P (\frac {\partial T} {\partial v})_P$$ and using some Maxwell relations but it doesn't work very well.
I know that $$T = (\frac {\partial H} {\partial S})_P$$ but I don't know how I would get to the answer.

I would be very happy if somone helped me.

Thanks.
 
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  • #2
All you need to do is to use the gas law. The Maxwell relation is unnecessary for this problem.
 

FAQ: Enthalpy derivation differential equation

What is enthalpy and how is it defined?

Enthalpy is a thermodynamic property that represents the total heat content of a system. It is defined as the sum of the internal energy of the system plus the product of its pressure and volume. Mathematically, it is expressed as H = U + PV, where H is enthalpy, U is internal energy, P is pressure, and V is volume.

What is the significance of the enthalpy differential equation?

The enthalpy differential equation is significant because it allows us to understand how enthalpy changes with respect to variables such as temperature and pressure. It provides a mathematical framework to analyze thermodynamic processes, particularly in relation to heat transfer and work done on or by the system.

How is the enthalpy differential equation derived?

The enthalpy differential equation is derived from the definition of enthalpy and the first law of thermodynamics. By taking the total differential of the enthalpy equation (H = U + PV) and applying the product rule, we can express the changes in enthalpy in terms of changes in internal energy, pressure, volume, temperature, and other state variables.

What are the common forms of the enthalpy differential equation?

The common forms of the enthalpy differential equation include the following: dH = dU + PdV + VdP. In many cases, particularly for processes at constant pressure, it simplifies to dH = dQ + VdP, where dQ is the heat added to the system, highlighting the relationship between heat transfer and enthalpy change.

How does the enthalpy differential equation apply to phase changes?

The enthalpy differential equation is particularly useful in analyzing phase changes, such as melting or boiling, where heat is added or removed at constant temperature and pressure. During these processes, the enthalpy change (ΔH) can be calculated using the heat of transformation, allowing for the prediction of energy requirements for phase transitions.

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