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The mole fraction of this component n i of gas mixture is called the relation of moles
of this component N i to moles of gas mixture N and equals a by volume partial:
N 
n i  i  i  r i (1.14)
N V
The sum of mole fraction of components of the gas mixture also equals unit.
The relation between mass fraction and volume fraction of gas mixture
 g 
 i 
m  r   i 


r
g  i  i i , or i  (1.15)
i
M    q  
сум i i
Molecular mass of gas mixture which set by volume fraction is determined as a
 сум    i r , (1.16)
i
where  - molar mass of i a components of gas mixture;
i
r
i - a volume fraction of components of gas mixture.

For finding of specific gas constant it is possible to take advantage of formulas
R 8314 1
R сум   , або R  (1.17)
   r сум  r 
сум i i  i
 
 R 
 i 
Partial pressure of the mixed gas components we can a find, when it is known
absolute pressure

P  Pr (1.18)
i
i

Below given different equations for gas mixture

n 1 1 n n n
v   q v      r  8314 1 g i
с i i n r ; c n  i i ; R c  n  n   q i R i  8314 
   i  r  i  i i
 i 1 i g i 1 r 1 1 
 i 1 v i  i 1  i 1  i 1 R
i

g
i
 g n r  r  R 
r  i  i  1 q  i i  i i r P  q i P  q c
r
i n g  c ;  с   i i  n q ; i n  ; P  i i R i  P ;
i
 i i  i 1  i  r  i c c i
i
1  i  i 1  i i1

1.5 Caloric variables of state
Caloric variables of state are internal energy U, entropy S and enthalpy H.
1.6.1 Internal energy U
Suppose the position of the piston in fig.1 is kept fixed at one place so that volume
of the gas remains constant, equal to V. If we heat the inside gas, its temperature and
pressure will increase. Where does the heat energy go?
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