On Mon, 27 Jan 2003 19:39:03 -0500 (EST), Henry Spencer <[EMAIL PROTECTED]> wrote:
>> 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.) 15* C is correct. >> 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. So I did it right (for a BOTE) the first time...I'll cheerfully accept a 0.56% percent on a BOTE, and that 's probably the argon. >> 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. 1.225 kg/m^3 for air = 1.225 g/dm^3 22.4 dm^3/mol Multiply: result is 27.44 g/mol for air Molecular weight of air =~ 28.8 Molecular weight of H2 =~ 2 Factor is 14.4 Molar weight of H2 = (27.44 / 14.4) = 1.906. I get a density of 0.085, BTW. So at least I'm consistent. Oh bother. Never mind. Boy, air temperature is more important than I realized. I've been using ICAO 76, which is not I say again not STP. As Henry speculated, ICAO temp is 15* C. The difference is 5.5%, almost exactly my error in the H2 density. -R -- "We've all heard that a million monkeys banging on a million typewriters will eventually reproduce the entire works of Shakespeare. Now, thanks to the Internet, we know this is not true." -- Robert Wilensky, UC Berkeley _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
