How to Find Specific Gas Constant For Any Gas? & What is Real Gas Equation?

There are some important terms like pressure, volume, temperature, enthalpy, entropy, internal energy in thermodynamics. These are properties and point functions.

Among these all properties Pressure, Volume an Temperature are basic, all other properties of thermodynamics are derived by using these three basics one. Relationship between these basic properties can be give as “PV=NR’T” . 

                        ( where,  R’= Universal Gas Constant=8.314j/mol.k

                                                                

                           P,V&T= Pressur, volume and temperature of gas

           n = no. of moles=total mass of gas/ molecular weight= m/M)

so, we can write above equation as  PV = (m/M)R’T

now apply this equation for air. Now as u all know molecular mass for air is M =28.96 kg/mol. Now u can fine specific gas constant R for air by this formula

R=     R’/M    =  8.314/28.96     =   0.287   kj / kg k

NOTE : now here, this thing should be noted that value of specific gas constant is 0.287 kj/mol.k is only for air, if gas changes show as this constant R. for example for NITROGEN value of ideal gas constant will be R_n2 = R’/molecular mass of nitrogen

So our equation will be  ”. like       “PV= mRT ( This is and ideal gas equation and m is mass of gas).

Here we have taken two assumption to assume any gas as an ideal gas. These assumption are as follow:

        I.            Volume occupied by molecules of gas is negligible.

      II.            There is no attraction between molecular of gas.

Þ    Now if someone wants to use above ideal gas equation for all real gases then he can do so but first of all he needs to add some parameters to eliminated assumption taken above.difference between real gas and ideal gas

·        a = this parameter eliminates our first assumption

·        b= this parameter eliminates out second assumption

Now if u add this parameters in ideal gas energy equation then your equation can also be used for REAL GAS  and it can be written as :

(P + a/V^2) (V-b)= RT  ( here m = unity )

 For more information about real gas click here