Vapor Density of Gas

on . Posted in Classical Mechanics

Vapor density is a measure of the density of a gas or vapor compared to the density of a reference gas.  The reference gas is typically air, which is assigned a vapor density of 1.  The vapor density of a gas is useful for various purposes, including determining whether a gas will rise or sink in air.  Gases with a vapor density less than 1 are lighter than air and will tend to rise, while gases with a vapor density greater than 1 are heavier than air and will tend to sink.

Vapor density example

  • Hydrogen gas (H2) has a molar mass of approximately 2 grams per mole, so its vapor density is 1 (2/2).
  • Carbon dioxide gas (CO2) has a molar mass of approximately 44 grams per mole, so its vapor density is 22 (44/2), indicating that it is much heavier than air.

 

Vapor Density of Gas formula

\( G_{vd} =  G \;/\; H \)     (Vapor Density of Gas)

\( G = G_{vd} \; H \)

\( H =  G \;/\; G_{vd} \)

Symbol English Metric
\(\large{ G_{vd} }\) = vapor density of gas \(lbm \;/\; ft^3\)  \(kg \;/\; m^3\) 
\(\large{ G }\) = gas density \(lbm \;/\; ft^3\)  \(kg \;/\; m^3\) 
\(\large{ H }\) = hydrogen density \(lbm \;/\; ft^3\)  \(kg \;/\; m^3\) 


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Tags: Gas Density Vapor