so i'm sitting in the dome watching (insert any team) prepare to score another TD on the saints and my mind wanders...what else is there to do?

so you make the superdome an absolute vacuum. now, you have a mayonnaise (ok, miracle whip) jar filled with oxygen. open the jar in the dome. according to the laws of chemistry gas conforms to its container right?
so does the oxygen expand to the area of the dome? i know it's not breathable, but would you detect oxygen down on the field and at the top at the seats that i can afford?

You couldn't, I couldn't, and possibly no instrument could. According to Wikipedia, the Superdome has an interior space of 125,000,000 cubic feet, or 3,500,000 cubic meters.

A quart (the official unit of measurement for mayo) is 946 ml, which is .000946 cubic meters. Dividing the volume (interior space) of the Superdome by .000946 gives you how many jars of oxygen would be necessary to fill the Dome.

3,500,000/.000946 = 3,699,788,582

In other words, an instrument would need to be able to detect one part of oxygen in 3.7 billion. Methos will probably be able to say if this is possible.

According to the Illinois Institute of Technology, a shark can detect blood in concentrations of 1 part per million. The instrument would need to be over 300 times as sensitive as a shark. (Compare to a bloodhound, whose nose is ten to a hundred million times more sensitive than a human's.)

The answer is two-fold. If you're asking whether oxygen would expand to fill every nook and cranny of the enclosed space, the answer is a resounding YES. The molecules would immediately wander out of the jar at supersonic velocities and randomly diffuse to fill the space in fairly short order.

They won't even be impeded by collisions with air molecules, as would normally occur if you opened a jar of gas under ordinary circumstances.

But since you asked about DETECTING the oxygen, it's a little more problematic, as DG has alluded to. You didn't specify the pressure the oxygen is under in the sealed jar before opening it, though there are limits to how much O₂ you can cram into a Miracle Whip jar before the glass bursts.

Taking DG's stadium volume figure of 3.5x10⁶ liters (seems low to me), and remembering from high school chemistry that one mole (6x10²³ molecules) occupies 22.4 liters at 1 atmosphere and 0 Deg C, and generously assuming the jar has a volume of one liter which is .001 cubic meters, then the gas is diluted to a final concentration of about 7.6x10¹² molecules/liter. If the oxygen is pressurized in the jar, there will be a correspondingly higher concentration after you let it out, though at room temperature the concentration will be some 10% lower than at the freezing point of water. This is, of course, a -- um -- ballpark figure.

I don't know just how sensitive oxygen detectors can be, but I should point out that the antennae of female gypsy moths contain chemical receptors for sexual pheromones emitted by male gypsy moths that reportedly respond to concentration gradients so low that individual molecules are detected. It's surely plausible that oxygen will be detectable at the concentrations, calculated above, by existing technology.

"This is, of course, a -- um -- ballpark figure."

And people complain about my terrible puns.

As Prof. said, yes, the oxygen atoms would spread to "fill every nook and cranny."

I suspect that's all you were really asking, but the detection question is interesting. Would an instrument be able to detect this? I don't know whether any exist, becaude this is a very odd situation, but (given the money) I think I could make one. The amount of light absorbed by a substance is proportional to the concentration and the pathlength the light travels through. Think about a powdered drink - the more you add to water, the darker the water gets, and the wider the glass, the darker it looks. Since you've got a whole stadium here, your pathlength could be very very long, allowing you to detect very low concentrations. Normally, you'd have to worry about light losses by scattering or absorbtion by other substances, but since oxygen is the only thing present here, you don't have to worry about that. If that wasn't enough, you could use something called cavity ringdown, where a pulse of light is bounced back and forth through between two mirrors (with the sample inbetween them). The pathlength, then, becomes very very large.

I dont think a shark's detection limit for blood tells us much about this situation. Humans can detect 2,4,6 trichloroanisole at about 2 parts per trillion. That's the stuff that makes wine taste corked. That might be the record for humans, but it's hardly the only thing we can taste below a part per million. We can taste sugar (sucrose) at (according to Wikipedia and a few unit conversions) 30 parts per billion. We can taste artificial sweetners at hundreds or thousands (depending on the sweetner) of times lower concentrations. Capsaicin, the stuff that makes peppers hot, can also be tasted well below one part per million. Our sense of smell is generally much more sensitive than our sense of taste. Of course, neither we nor sharks would be able to detect oxygen at these concentrations without instruments.

Now, what is a part per million? I'm afraid DG's got it wrong. Parts per million is a relative measurement of mass per mass, volume per volume, or mass per volume. The latter is often used for liquids and assumes that the liquid has a mass of about 1 kilogram per liter (in other words, it's really an approximation of mass per mass). Since it's a relative concentration, and the only thing there is oxygen, the concentration of oxygen is 1 million parts per million. It's the same sort of unit as percent (1 part per million = 0.0001%). Since all we've got is oxygen, it's 100% oxygen whether it's in a 1 liter container or in a 3,500,000 cubic meter container. This doesn't tell us much, so it's not a particularly useful measure in this situation.

This message has been edited. Last edited by: methos,

In my post above, I meant to say that the final concentration would be about 7.6x10¹² molecules per cubic meter, not per liter.

yeah, i was intrested in knowing if the amount of air in the jar would expand and spread thoughout the dome. i thought it would.

thanks for all your answers.