Gases

Volume of Gases

• The Molar volume ($V_m$) of a substance is the ration of the volume occupied by a substance to the amount of substance.
  • $V_m=\frac{M}{\rho }$, where:
    • $V_m$ is the molar volume of the substance (in ${\mathrm{m}}^3/mol$)
    • $M$ is the molar mass of the substance (in $g/mol$)
    • $\rho$ is the density of the substance (in $g/{\mathrm{m}}^3$)

Ideal Gas Law

The ideal gas law is the equation of state for an ideal gas, given by

$PV=nRT$

where:

• $P$ is the pressure
• $V$ is the volume
• $n$ is the amount of substance of the gas (in moles)
• $T$ is the absolute temperature
• $R$ is the gas constant
  • $R$ must be expressed in units consistent with those chosen for pressure, volume and temperature.
  • For example, when pressure is expressed in pascals, volume in cubic meters, and absolute temperature in kelvin, the value of the gas constant is $R=8.3145\mathsf{J}\cdot {\mathsf{K}}^{-1}\cdot \mathsf{mo}{\mathsf{l}}^{-1}$.