On Mon, 27 Jan 2003, Randall Clague wrote:
> N atomic weight: 14
> O atomic weight: 16
Neither is spot-on, but as it happens both are very close.
> H2 molecular weight: 2
A touch low, as noted, but not much.
> ICAO sea level density of air: 1.225 kg/m^3
> liters per mole at STP: 22.4
What temperature is the ICAO number at? STP is 0degC 760torr, and air
at that temperature is 1.2928kg/m^3, it says here. (Hmm, the accompanying
table for near-STP conditions would give 1.225 at 15degC 760torr.)
> Oh bother. 14.4 is 20% N 80% O.
Nope, 14.4 is 80%N, 20%O. Note, however, that the atmosphere is just over
78%N, just under 21%O, and just under 1%Ar (atomic weight = molecular
weight = about 40). The molecular weight of air is about 28.96.
> With 15.6 I get...2.06 g/mol. Still a 3% error.
I'm a little unsure how you're computing this. Density of hydrogen at STP
is 0.0899kg/m^3, which would make 22.4 liters of it 2.01376g, just about
right.
Henry Spencer
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