Vapour density

Vapour density is the density of a vapour in relation to that of hydrogen. It 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 gas .
vapour density = molar mass of gas / molar mass of H2
vapour density = molar mass of gas / 2.01568
vapour density = 1⁄2 × molar mass

(and thus: molar mass = ~2 × vapour density) For example, vapour density of mixture of NO2 and N2O4 is 38.3. Vapour density is a dimensionless quantity.


Vapour density = density of gas / density of hydrogen (H2)

Alternative definition

In many web sources, particularly in relation to safety considerations at commercial and industrial facilities in the U.S., vapour density is defined with respect to air, not hydrogen.[1] Air is given a vapour density of one. For this use, air has a molecular weight of 28.97 atomic mass units, and all other gas and vapour molecular weights are divided by this number to derive their vapour density.[2] For example, acetone has a vapour density of 2[3] in relation to air. That means acetone vapour is twice as heavy as air. This can be seen by dividing the molecular weight of Acetone, 58.1[4] by that of air, 28.97, which equals 2.

With this definition, the vapour density would indicate whether a gas is denser (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, possibly presenting an asphyxiation hazard to individuals entering the lower part of that space.

See also

References

  1. ^ MSDS Glossary of Terms – Vapour Density. Msdsonline.com. Retrieved on 2012-02-09.
  2. ^ HazMat Math: Calculating Vapor Density Archived 2011-07-11 at the Wayback Machine. Firenuggets.com. Retrieved on 2012-02-09.
  3. ^ "MSDS: Acetone". hazard.com. 1998-04-21. Archived from the original on 2021-09-23. Retrieved 2012-02-09.
  4. ^ NIOSH Pocket Guide: Acetone. Cdc.gov. Retrieved on 2012-02-09.


Stub icon

This fluid dynamics–related article is a stub. You can help Wikipedia by adding missing information.

Content Disclaimer

Informasi ini disarikan dari Wikipedia dan disajikan kembali untuk tujuan edukasi. Konten tersedia di bawah lisensi CC BY-SA 3.0. Kami tidak bertanggung jawab atas ketidakakuratan data yang bersumber dari kontribusi publik tersebut.

  1. The information displayed on this website is sourced in part or in whole from Wikipedia and has been adapted for the purpose of restating it. We strive to provide accurate and relevant information, however:
  2. There is no guarantee of absolute accuracy. Wikipedia is an open, collaborative project that can be edited by anyone, so information is subject to change.
  3. It is not intended to constitute professional advice. The content displayed is for informational and educational purposes only. For important decisions (e.g., medical, legal, or financial), please consult a professional.
  4. Content copyright. Wikipedia is licensed under the Creative Commons Attribution-ShareAlike License (CC BY-SA). This means that content may be reused with appropriate attribution and shared under a similar license.
  5. Responsible use. Any risk arising from the use of information from this website is entirely the responsibility of the user.