Physics Help Forum Problem on ratio of mass of gas

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 Jun 15th 2008, 07:52 PM #1 Senior Member   Join Date: Apr 2008 Location: HK Posts: 886 Problem on ratio of mass of gas There are flasks X and Y which are connected by a thin tube. T. Volume of X is twice that of Y.Both flasks are filled with an ideal gas and a steady state is established with the flask X and Y held with the flasks X and Y held at 200K and 400K respectively. What is the ratio of the mass of gas in X to that in Y? I guess it is to consider the volume ration regarding mass of gas. However, I don't know how to deal with the statement " steady state is established with the flask X and Y held with the flasks X and Y held at 200K and 400K respectively". Why is the answer 4:1 ?
Jun 16th 2008, 05:29 AM   #2

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 Originally Posted by werehk There are flasks X and Y which are connected by a thin tube. T. Volume of X is twice that of Y.Both flasks are filled with an ideal gas and a steady state is established with the flask X and Y held with the flasks X and Y held at 200K and 400K respectively. What is the ratio of the mass of gas in X to that in Y? I guess it is to consider the volume ration regarding mass of gas. However, I don't know how to deal with the statement " steady state is established with the flask X and Y held with the flasks X and Y held at 200K and 400K respectively". Why is the answer 4:1 ?
There's something about this problem that doesn't seem to make sense. If the connecting tube is not open, we don't require any specific temperature for equilibrium. If the connecting tube is open then the gases mix and the difference in temperature between the two flasks means that we cannot have equilibrium.

Where did this problem come from? Perhaps "steady state" in this case is not what I am thinking it should be.

-Dan
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 Jun 17th 2008, 08:29 PM #3 Senior Member   Join Date: Apr 2008 Location: HK Posts: 886 The question comes from Hong Kong AL which is of many years ago. There may be some error. But regarding the answer, would the equation relating temperature, volume and pressure help?
Jun 18th 2008, 04:18 AM   #4

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 Originally Posted by werehk The question comes from Hong Kong AL which is of many years ago. There may be some error. But regarding the answer, would the equation relating temperature, volume and pressure help?
The problem I am having is that there can be no static equilibrium state due to the difference in temperature, so any "steady state" solution would need to be a dynamic equilibrium. But the pressure and volume of an ideal gas does not depend on the mass of the gas so this should not be a factor in the problem. I cannot see how to proceed.

However Thermodynamics was never one of my specialties...

-Dan
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