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PV  MRT (1.8)
,
or for 1 kg gas Pv  R T (1.9)
 ,

where v =V/M - specific volume

A gram mole (kilogram mole) of a substance is that amount of the substance whose
mass in grams (kg) is equal to the molecular weight of the substance. A mole of any
substance is that mass which contains a specified number of molecules, namely, 6.023
23
·10 , called the Avogadro’s number. Although the mole (kilogram mole) is a unit of
mass, we can not translate it into, say, grams, until we know the chemical composition
of the substance.
PV = NmRT, (1.10)
where N is the number of moles of the gas and m is the molar mass.

1.4 Gas mixtures
In practice we usually have to deal not with clean gases, but with their mixtures.
Such mixtures for example are products of combustion of fuel and natural gases. The
conduct of gas mixtures describes by Dalton’s law. Accordingly these law, pressure of
mixture of gases are equals the sum of partial pressures its component

P  P 1  P 2  P .....  P n   P (1.11)
n
3
where P - pressure of gas mixture, P 1, P 2… - partial pressures its components of gas
mixture.

A partial pressure of component of the gas mixture we call a pressure which could
create this component at the temperature of the gas mixture, when it occupied that
volume which occupies the gas mixture.
A partials volume of component of the gas mixture we call a volume which could
occupy this component at a temperature and pressure of the gas mixture.
The gas mixture can be set by mass fraction, volume fraction and mole fraction.

The mass fraction of this component of gas mixture g i, is called the relation of mass
of this component m i to mass of gas mixture M
m
g  i (1.12)
i
M

The sum of mass fraction of components of the gas mixture are equals unit -  g i  1
The volume partial of this component r i of the gas mixture is called relation of extent
of this component v i to the full volume V:

r  i
i (1.13)
V
The sum of volume fraction of components of the gas mixture equals unit -  i  1
r

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