CHEE2325 Thermodynamics Lecture 9 Summary

CHEE2325 – Lecture 9


Gas mixtures:
- Properties of nonreacting gas mixtures depends on the properties of the
individual gases (components, denoted by i ), as well as the amount of each
gas in the mixture.
- Tables of properties exist for common mixtures, such as air, however, it is
impractical to prepare property tables for every conceivable mixture
composition, as the number of possible compositions is infinite.
- To determine the properties of a mixture, the:
o composition of the mixture,
o properties of the individual components,
must be known.
- When working with gas mixtures, there are two types of analysis:
o Molar analysis: by specifying the number of moles of each component.
o Gravimetric analysis: by specifying the mass of each component.



Mass and mole fraction:
- Consider a gas mixture of k components.
- The mass of the mixture, mm, is the sum of the individual components.
- The mass fraction of a component is given by:
mi
m f i=
mm

- The mole number of the mixture, N m , is the sum of the mole numbers of the
individual components.
- The mole fraction of a component is given by:
Ni
y i=
Nm



Gas mixtures average:
- The mass of a component is given by:
mi=N i M i

- The apparent, or average, molar mass, is given by: