My non-scientific opinion…
Yes, you could submerge it with enough weight attached.
No, you would not see the bubbles, unless there was an obvious hole in the balloon. If you are thinking in terms of the small amount of helium that passes through the wall of the balloon, I would think it would be dissolved or absorbed into the water. However, if you added a really big weight and sank the balloon to a really great depth, the water pressure might squeeze the helium out fast enough to see bubbles. In that case, my answer is maybe.
The helium would leak out of the balloon.
The constriction caused by the balloon creates higher pressure inside the balloon than outside the balloon. The helium would leak out until the pressure inside the balloon is equal to the pressure outside the balloon. At which point the balloon would be pretty much flat.
The air tight container has no effect unless you are using it to somehow artificially manipulate the air pressure around the balloon.
Wheelrider is correct in his assessment given what you have asked. If you put the He baloon in an airtight container that has the same pressure as that inside the baloon, the Helium would still diffuse through the baloon and mix with the air outside. In fact, if you waited long enough, the gas mixtures inside and outside the baloon would be the same. This is because the He atoms and air molecules act independently, and since there is an initial gradient (caused by the membrane of the baloon) there is a flux across that gradient.
Repeat after me; Every gradient demands a flux
This is of course a mystery. My mother’s womb would be an accurate, although flippant, response
A Coker tire contains about 6 liters of gas at STP. They are usually filled to about 3 atmospheres which would be equivalent to about 18 liters of gas. There are 22 some liters of gas in one mole. We can say 18 is about 22 or we put a bit more pressure in our tire so let’s say that a full Coker tire has a mole of gas in it. A mole of helium, a monatomic gas of mass 4, is 4 grams. A mole of nitrogen, a diatomic molecular gas of mass 28, is 28 grams. The bouyant forces are of course identical. The nitrogen filled tire has 24 grams more mass than the helium filled tire. This is a little less than an ounce. Is this enough to warrant further discussion? If you want to get rid of an ounce, take the change out of your pocket.
Ah, here we have our Engineer. Close enough Mr. Harper, you pass.
However the biggest weight-weenies are trials riders, and they use much smaller tyres and lower pressures. Anyone any idea of the volume of one?
I want to guess…
2.5 Litres of gas.
Maybe someone could try hydogen. Watch out for naked flames though. Oh the humanity!
Unless you had some huge knobby tire (a huge knobby COKER tire… I don’t think I will see the day), there would not be enough He in the tire to make a difference. Even in Harper’s example, it was a little less than one ounce, which would not make a huge difference in a trials unicycle, it is only 1/16 of a pound. Making a trials unicycle’s weight go from say… 14 pounds to 13.9375 is not going to make the slightest difference in hop height.
Someone correct me on my math if it is incorrect.