Vapour density

From Wikipedia, the free encyclopedia

Vapour density is the density of a vapour in relation to that of hydrogen.May be defined as mass of a certain volume of a substance divided by mass of same volume of hydrogen.

vapour density= mass of n molecules of gas/ mass of n molecules of hydrogen

by definition molar mass of a gas is the ratio of the mass of one molecule of gas to that of an hydrogen atom under similar conditions

so, vapour density = 1/2 molar mass

[edit] See also

In many web sources, the vapour density is defined with respect to air, not hydrogen. With this definition, the vapour density would indicate whether a gas is more dense (greater than one) or less dense (less than one) than air. The density has implications for container storage and personnel safety--if a container can release a dense gas, its vapour could sink and, if flammable, collect until it is at a concentration sufficient for ignition. Even if not flammable, it could collect in the lower floor or level of a confined space and displace air, to present a smothering hazard to individuals entering the lower part of that space.

It is recommended that individuals confirm the definition of vapour density being used in their specific context.