Well Sam, the first thing that comes to mind is the the U-tube expirement. This is with relation to the mercury level at atmospheric pressure, which is 750Hg or 7.5mm or something like that. Please, I am not sure of this numeric/unit so . Anyhow.
The thing-to-do is *get a Utube *fill it with mercury; make sure the mercury is leveled (as in, at the same mark on both sides) *now pour some oxygen into one limb (OR push one limb into some oxygen source_ I am sure you can figure somthing out) *and........then you measure the difference in the two (upper levels) of the liquid and.......... (drum roll.......) TA DA!
quote:Originally posted by Pin~Jinx: Well Sam, the first thing that comes to mind is the the U-tube expirement. This is with relation to the mercury level at atmospheric pressure, which is 750Hg or 7.5mm or something like that. Please, I am not sure of this numeric/unit so . Anyhow.
The thing-to-do is *get a Utube *fill it with mercury; make sure the mercury is leveled (as in, at the same mark on both sides) *now pour some oxygen into one limb (OR push one limb into some oxygen source_ I am sure you can figure somthing out) *and........then you measure the difference in the two (upper levels) of the liquid and.......... (drum roll.......) TA DA!
Confused Confused Um thanks.for the answer... now i'm sure i can figure it out.. Eek
01-15-03, 08:26 AM FlyingHellfish Dalton's Law of Partial Pressures states that the total pressure of a gas mixture equals the sum of the partial pressures that make up the mixture, given that no gases undergo a chemical reaction. Basically, each of the gases behaves their own way, and each adds to the sum as if it were the only gas in the mixture. For example, if you add a .5 atm bit of Helium to a 2 atm container of Neon, then the total pressure of the mixture will be 2.5 atm (1 atm = 1 atmosphere = 14.7 psi = 760mm Hg). For simplicity, "air" is made up of approximately 80% Nitrogen and 20% Oxygen (of course, there's more in there, but in very small amounts). Our atmosphere has an approximate pressure of 760mm Hg, so 80% of that pressure comes from Nitrogen and 20% of the comes from Oxygen. 20% * 760mm Hg = 152mm Hg = 2.94 psi of gas pressure comes from Oxygen in air.
01-15-03, 10:25 AM gerry FlyingHellfish' response is excellent. I want to point out, however, that the figures apply to average atmospheric/oxygen pressure at sea level. When you go higher up into the atmosphere, these pressures drastically reduce. Atmospheric pressure at commercial jet altitudes of 35 to 40,000 feet would be in the order of only 3 psi, and the corresponding partial pressure of oxygen would only be about a half of a psi.
01-15-03, 10:25 AM samantha This is what i needed...Thanks so much! Cool
01-15-03, 10:31 AM samantha Thank you too gerry for the information on that... Big Grin
01-20-03, 07:41 PM Peteeo From Chemical Principals by Masterton & Slowinski.
Dalton's law is the one that applies.
P=nrt/v=(Na+Nb+Nc)*RT/V Na = moles of A Nb= moles of B Nc= Moles of C.
Distributin the RT/V to each..you can manipulate the equation to show that P(a)+P(b)+P(c) = P total..
Air by molar fraction is 78% Nitrogen, 21% Oxygen and 1 % Argon + traces...
Taking the current barometric pressure.
P* 0.21 (mole fraction of O2)= P(O2).
So if the pressure outside is 742 mm HG. 0.21*742= 160 mm Hg partial pressure O2
01-21-03, 06:43 AM WiteoutKing .21*742 yields 155.82, Peteeo.
01-22-03, 11:26 AM cibby Don't they teach significant figures anymore?? I hope I'm not being too preachy here but it does seem like quite a few people could benefit from a lesson about significant figures.Too many people think by recording all the numbers their calculator gives them they're being extremely accurate, when in fact what they're really doing is incorrectly claiming each number means something.
The percent oxygen in air value of 21% contains only two significant figures and the pressure of 742 mm Hg contains only three significant figures. It therefore makes no sense to claim the answer is accurate to 5 significant figures. In fact the answer can not contain more than 2 significant figures (the number with the least significant figures)... so regardless of what your calculator says 160 is a better answer than 155.82
01-22-03, 11:36 AM methos WiteoutKing - I'd have to side with Peteeo and cibby on that... on the other hand I have been 'yelled' at here for being nitpicky like that ;-)
01-22-03, 01:40 PM WiteoutKing Well, if the percentage was a longer, "exact" percentage, it would need three, and if you made the numbers more exact, your sig-figs would grow. I don't know much about psis, so I can't argue figures.
btw, I wasn't adding the number of sig-figs, I was simply multiplying your figures. I know how to do sig-fig.
01-22-03, 02:23 PM methos WiteoutKing - I think everyone realizes that you were simply multiplying the figures. What cibby was saying is you did not need to correct Peteeo's answer because, in science, 0.21*742 does indeed equal 160, so his answer was correct to begin with. My assumption is that this is for some sort of class (could be wrong), and most chemistry classes at least would have taken off points for not rounding off to 160 mm Hg, so we were just helping samantha out.
01-25-03, 11:37 PM WiteoutKing sry bout that, I think I came across as kinda rude.
01-26-03, 03:22 AM samantha thanks so much for all your help on here and your answers to my question. I really appreciate it alot.
This message has been edited. Last edited by: DorianGreyed,
