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Se obtienen mediante la función partición las distintas funciones y relaciones termodinámicas.

>Model

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Helmholtz free energy with partition function

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As the derivative with respect to the volume of the free energy of Helmholtz at constant temperature is:

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Differential relation Helmholtz Free Energy

Equation

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Since the Helmholtz free energy depends on the temperature $T$ and volume $V$, the differential is obtained as:

$ F = U - T S $



where:

$ dF =- S dT - p dV $

$dF$
Differential Helmholtz Free Energy
$J$
$S$
Entropy
$J/K$
$p$
Pressure
$Pa$
$dT$
Temperature variation
$K$
$dV$
Volume Variation
$m^3$

If we differentiate the definition of Helmholtz free energy:

$ F = U - T S $



we obtain:

$dF = dU - TdS - SdT$



With the differential of internal energy:

$ dU = T dS - p dV $



we can conclude that:

$ dF =- S dT - p dV $

ID:(3474, 0)



Differential of Helmholtz Free Energy

Equation

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Given that the helmholtz free fnergy ($F$) is a function of the absolute temperature ($T$) and the volume ($V$), we can express the differential enthalpy ($dH$) as follows:

$dF=\left(\displaystyle\frac{\partial F}{\partial T}\right)_VdT+\left(\displaystyle\frac{\partial F}{\partial V}\right)_TdV$



This allows us to define the differential Helmholtz Free Energy ($dF$) in terms of the slopes the partial derivative of the Helmholtz free energy with respect to temperature at constant volume ($DF_{T,V}$) and the partial derivative of the Helmholtz free energy with respect to volume at constant temperature ($DF_{V,T}$):

$ dF = DF_{T,V} dT + DF_{V,T} dV $

$dF$
Differential Helmholtz Free Energy
$J$
$DF_{T,V}$
Partial derivative of the Helmholtz free energy with respect to temperature at constant volume
$J/K$
$DF_{V,T}$
Partial derivative of the Helmholtz free energy with respect to volume at constant temperature
$J/m^3$
$dT$
Temperature variation
$K$
$dV$
Volume Variation
$m^3$

ID:(8187, 0)



Calculo de la derivada parcial de la energía libre de Helmholtz en el volumen a temperatura constante

Equation

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La derivada de la energía interna en el volumen a entropia constante es

$ DF_{V,T} =\left(\displaystyle\frac{\partial F }{\partial V }\right)_ T $

$T$
Absolute temperature
$K$
$F$
Helmholtz free fnergy
$J$
$DF_{V,T}$
Partial derivative of the Helmholtz free energy with respect to volume at constant temperature
$J/m^3$
$V$
Volume
$m^3$

ID:(12416, 0)



Calculo de la derivada parcial de la energía libre de Helmholtz en la temperatura a volumen constante

Equation

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La derivada de la energía interna en el volumen a entropia constante es

$ DF_{T,V} =\left(\displaystyle\frac{\partial F }{\partial T }\right)_ V $

$T$
Absolute temperature
$K$
$F$
Helmholtz free fnergy
$J$
$DF_{T,V}$
Partial derivative of the Helmholtz free energy with respect to temperature at constant volume
$J/K$
$V$
Volume
$m^3$

ID:(12417, 0)



Helmholtz Free Energy and Equation of State at Constant Volume

Equation

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The differential Helmholtz Free Energy ($dF$) is a function of the variations in the absolute temperature ($T$) and the volume ($V$), as well as the slopes the partial derivative of the Helmholtz free energy with respect to temperature at constant volume ($DF_{T,V}$) and the partial derivative of the Helmholtz free energy with respect to volume at constant temperature ($DF_{V,T}$), which is expressed as:

$ dF = DF_{T,V} dT + DF_{V,T} dV $



Comparing this with the first law of thermodynamics, it turns out that the partial derivative of the Helmholtz free energy with respect to temperature at constant volume ($DF_{T,V}$) is equal to minus the entropy ($S$):

$ DF_{T,V} =- S $

$S$
Entropy
$J/K$
$DF_{T,V}$
Partial derivative of the Helmholtz free energy with respect to temperature at constant volume
$J/K$

ID:(3550, 0)



Helmholtz Free Energy and Equation of State at Constant Temperature

Equation

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The differential Helmholtz Free Energy ($dF$) is a function of the variations in the absolute temperature ($T$) and the volume ($V$), as well as the slopes the partial derivative of the Helmholtz free energy with respect to temperature at constant volume ($DF_{T,V}$) and the partial derivative of the Helmholtz free energy with respect to volume at constant temperature ($DF_{V,T}$), which is expressed as:

$ dF = DF_{T,V} dT + DF_{V,T} dV $



Comparing this with the first law of thermodynamics, it turns out that the partial derivative of the Helmholtz free energy with respect to volume at constant temperature ($DF_{V,T}$) is equal to minus the pressure ($p$):

$ DF_{V,T} =- p $

$DF_{V,T}$
Partial derivative of the Helmholtz free energy with respect to volume at constant temperature
$J/m^3$
$p$
Pressure
$Pa$

ID:(3551, 0)



Helmholtz free energy with partition function

Equation

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Como la derivada respecto del volumen de la energía libre de Helmholtz a temperatura constante es con partial derivative of the Helmholtz free energy with respect to volume at constant temperature $J/m^3$ and pressure $Pa$

$ DF_{V,T} =- p $



y la presión es con igual a

$\bar{p}=\displaystyle\frac{1}{\beta}\displaystyle\frac{\partial\ln Z}{\partial V}$



se tiene que la energía libre de Helmholtz es con

$ F =-\displaystyle\frac{1}{ \beta }\ln Z $

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Helmholtz Free Energy and its Relation of Maxwell

Equation

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Since the helmholtz free fnergy ($F$) is an exact differential, it means that you can first vary the absolute temperature ($T$) and then the volume ($V$), or in the reverse order, and the result will be the same. This can be expressed by taking derivatives of slopes in different orders, and there will be no difference:

$D(DF_{T,V})_{V,T}=D(DF_{V,T})_{T,V}$



If you replace the differential with the corresponding variable, you obtain the relationship involving the entropy ($S$) and the pressure ($p$):

$ DS_{V,T} = Dp_{T,V} $

$DS_{V,T}$
Partial derivative of entropy with respect to volume at constant temperature
$J/m^3$
$Dp_{T,V}$
Partial derivative of pressure with respect to temperature at constant volume
$Pa/K$

Since the differential Helmholtz Free Energy ($dF$) is an exact differential, we should note that the helmholtz free fnergy ($F$) with respect to the absolute temperature ($T$) and the volume ($V$) must be independent of the order in which the function is derived:

$D(DF_{T,V})_{V,T}=D(DF{V,T})_{T,V}$



Using the relationship between the slope the partial derivative of the Helmholtz free energy with respect to temperature at constant volume ($DF_{T,V}$) and the entropy ($S$)

$ DF_{T,V} =- S $

,

and the relationship between the slope the partial derivative of the Helmholtz free energy with respect to volume at constant temperature ($DF_{V,T}$) and the pressure ($p$)

$ DF_{V,T} =- p $

,

we can conclude that:

$ DS_{V,T} = Dp_{T,V} $

ID:(3554, 0)



Calculo de la derivada parcial de la entropía en el volumen a temperatura constante

Equation

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La derivada de la entropía en el volumen a temperatura constante es

$ DS_{V,T} =\left(\displaystyle\frac{\partial S }{\partial V }\right)_ T $

$T$
Absolute temperature
$K$
$S$
Entropy
$J/K$
$DS_{V,T}$
Partial derivative of entropy with respect to volume at constant temperature
$J/m^3$
$V$
Volume
$m^3$

ID:(12422, 0)



Calculo de la derivada parcial de la presión en la temperatura a volumen constante

Equation

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La derivada de la presión en la temperatura a volumen constante es

$ Dp_{T,V} =\left(\displaystyle\frac{\partial p }{\partial T }\right)_ V $

$T$
Absolute temperature
$K$
$Dp_{T,V}$
Partial derivative of pressure with respect to temperature at constant volume
$Pa/K$
$p$
Pressure
$Pa$
$V$
Volume
$m^3$

ID:(12420, 0)



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Video

Video: Helmholtz Free Energy