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
Therefore:
vapour density = molar mass of gas / molar mass of H2
vapour density = molar mass of gas / 2.0016
vapour density = ~½ × molar mass
(and thus: molar mass = ~2 × vapour density)
Read more about Vapour Density: Alternative Definition
Famous quotes containing the word vapour:
“Thy great leaves enfold
The ancient beards, the helms of ruby and gold
Of the crowned Magi; and the king whose eyes
Saw the Pierced Hands and Rood of elder rise
In Druid vapour and make the torches dim....”
—William Butler Yeats (1865–1939)