Real Gas Law

Storyboard

In the case of an ideal gas, it is assumed that the molecules do not interact. If one wishes to model the behavior of a real gas in which there is interaction, one must consider the attraction between the molecules and the repulsion that prevent them from overlapping. The first has an effect above all on the edges of the system as it slows particles that move towards the edge. The attraction effectively reduces the pressure that the gas makes on the walls. On the other hand the repulsion acts as a reduction of the volume available to the particles creating a stiffness to compress it.

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Mechanisms

Definition


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Model

Image


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Real Gas Law

Storyboard

In the case of an ideal gas, it is assumed that the molecules do not interact. If one wishes to model the behavior of a real gas in which there is interaction, one must consider the attraction between the molecules and the repulsion that prevent them from overlapping. The first has an effect above all on the edges of the system as it slows particles that move towards the edge. The attraction effectively reduces the pressure that the gas makes on the walls. On the other hand the repulsion acts as a reduction of the volume available to the particles creating a stiffness to compress it.

Variables

Symbol
Text
Variable
Value
Units
Calculate
MKS Value
MKS Units
$T$
T
Absolute temperature
K
$C_a$
C_a
Constant of Avogadro's principle
mol/m^3
$\rho_z$
rho_z
Densidad en la Altura $z$
kg/m^3
$\rho$
rho
Density
kg/m^3
$M$
M
Mass
kg
$c_m$
c_m
Molar concentration
mol/m^3
$M_m$
M_m
Molar Mass
kg/mol
$n$
n
Número de Moles
mol
$p$
p
Pressure
Pa
$R_s$
R_s
Specific gas constant
J/kg K
$V$
V
Volume
m^3
$V_a$
V_a
Volumen
m^3

Calculations


First, select the equation:   to ,  then, select the variable:   to 

Symbol
Equation
Solved
Translated

Calculations

Symbol
Equation
Solved
Translated

 Variable   Given   Calculate   Target :   Equation   To be used



Equations

The pressure ($p$), the volume ($V$), the absolute temperature ($T$), and the number of moles ($n$) are related through the following physical laws:

• Boyle's law
equation=582

• Charles's law
equation=583

• Gay-Lussac's law
equation=581

• Avogadro's law
equation=580

These laws can be expressed in a more general form as:

$\displaystyle\frac{pV}{nT}=cte$



This general relationship states that the product of pressure and volume divided by the number of moles and temperature remains constant:

equation

When the pressure ($p$) behaves as an ideal gas, satisfying the volume ($V$), the number of moles ($n$), the absolute temperature ($T$), and the universal gas constant ($R_C$), the ideal gas equation:

equation=3183

and the definition of the molar concentration ($c_m$):

equation=4878

lead to the following relationship:

equation

The number of moles ($n$) corresponds to the number of particles ($N$) divided by the avogadro's number ($N_A$):

equation=3748

If we multiply both the numerator and the denominator by the particle mass ($m$), we obtain:

$n=\displaystyle\frac{N}{N_A}=\displaystyle\frac{Nm}{N_Am}=\displaystyle\frac{M}{M_m}$



So it is:

equation

The pressure ($p$) is associated with the volume ($V$), ERROR:6679, the absolute temperature ($T$), and the universal gas constant ($R_C$) through the equation:

equation=3183

Since ERROR:6679 can be calculated with the mass ($M$) and the molar Mass ($M_m$) using:

equation=4854

and obtained with the definition of the specific gas constant ($R_s$) using:

equation=8832

we conclude that:

equation


Examples


mechanisms


model

Avogadro's Law states that the volume ($V$) and the number of moles ($n$) are directly proportional when the pressure ($p$) and the absolute temperature ($T$) are held constant.

This relationship can be expressed as follows, using the constant of Avogadro's principle ($C_a$):

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The molar concentration ($c_m$) corresponds to ERROR:9339,0 divided by the volume ($V$) of a gas and is calculated as follows:

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The molar concentration ($c_m$) can be calculated from the density ($\rho$) and the molar Mass ($M_m$) as follows:

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The density ($\rho$) is a measure of the amount of the mass ($M$) contained in a the volume ($V$) and is defined as:

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The number of moles ($n$) is determined by dividing the mass ($M$) of a substance by its the molar Mass ($M_m$), which corresponds to the weight of one mole of the substance.

Therefore, the following relationship can be established:

kyon

The molar mass is expressed in grams per mole (g/mol).

The pressure ($p$), the volume ($V$), the absolute temperature ($T$), and the number of moles ($n$) are related by the following equation:

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where the universal gas constant ($R_C$) has a value of 8.314 J/K mol.

The pressure ($p$) can be calculated from the molar concentration ($c_m$) using the absolute temperature ($T$), and the universal gas constant ($R_C$) as follows:

kyon

The pressure ($p$) is related to the mass ($M$) with the volume ($V$), the specific gas constant ($R_s$), and the absolute temperature ($T$) through:

kyon


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