Gas Mixtures

Composition of Gas Mixtures

Gravimetric Analysis

Total mass of a mixture is equal to the sum of the mass of each component

Mass fraction — ratio of mass of component to the total mass of mixture: ${\text{mf}}_i=\frac{m_i}{m_m}$

Molar Analysis

Total number of moles in a non-reacting mixture is equal to the sum of the number of moles of each component

Mole fraction — ratio of mole number of a component to the total mole number of the mixture: $y_i=\frac{N_i}{N_m}$

Molar mass calculation

Mass of substance m is equal to the product of mole number N and molar mass M: $m=NM$

The molar mass can then be expressed in the following ways: $M_m=\frac{m_m}{N_m}=\frac{\sum m_i}{N_m}=\frac{\sum N_i{M}_i}{N_m}={\sum }_i^k{y}_i{M}_i$

$\text{OR:}$

$M_m=\frac{m_m}{N_m}=\frac{m_m}{\sum m_i/M_i}=\frac{m_m}{\sum m_i/(m_m{M}_i)}=\frac{1}{{\sum }_i^k\frac{{\text{mf}}_i}{M_i}}$

Gas Constant for mixture

$R_m=\frac{R_u}{M_m}{R}_u=8.314\text{ kJ/kmol}\cdot \text{K}$