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Dear all, see attached picture Please, is it possible to have the gas recirculated from the gas phase to the liquid as described in the diagram assuming the gas is not soluble in the water. These are the conditions. 1. The valve remained closed, 2. The liquid level didn’t change 3. P1 increases.

Could P1 get to a level where it would force itself through the pipe and go through the liquid. If P1 increases, what happens to P2.

enter image description here

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Please provide a link to the picture and somebody will edit your post to add it in. –  Brandon Enright May 10 '13 at 18:04
I can,t add the DIagram, I keep getting, You need at least 10 reputation to post images. –  Abiodun Jegede May 10 '13 at 18:07
You need at least 10 reputation to post images. I keep getting this message, I can't add the diagram, how can I solve that. –  Abiodun Jegede May 10 '13 at 18:08
@AbiodunJegede Put the link of the picture if it's on an image hosting site. Otherwise, upload it to one, then post the link. Example of image posting site. –  Jerry May 10 '13 at 18:18
Upload it somewhere and add a link. –  septi May 10 '13 at 18:18

2 Answers 2

up vote 2 down vote accepted

Ordinarily, no. In fact, the liquid level would usually rise in the tube until it is at the same height as in the main tank, so your gas would be very far from the end of the tube. To see why, imagine the surface of the liquid directly above the the end of the tube. The pressure is P1. That pressure gets transmitted through the liquid down to the end of the tube. But there's a second source of pressure there: the weight of the water above the end of the tube. So the pressure there is always greater than the pressure P1. The pressure in the gas, however, is always just about exactly P1. So any gas at the end of the tube would get forced back into the tube. It could never bubble out.

Now, maybe if I were to break enough rules, I could get a few bubbles briefly. But for an ordinary tank, with uniform pressures, ordinary materials, no relevant capillary actions, only gravity involved, etc., the answer is no. You need some sort of pump to raise the pressure in the tube, and make it different from the pressure in the gas directly above the liquid.

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In this case, $P_2 > P_1$. Therefore, of you look at the side tube, through which gas is supposed to flow, there is a pressure gradient that will oppose the flow of the gas.

But there is one more flaw in the experiment. The liquid itself will rise through the side tube to a height that matches the level in the main vessel. In that case, there will be same pressure, say $P_1^\prime$ at the surface of the liquid in the side tube and the main jar. In absence of a pressure gradient, there will be no flow either.

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