Problem: Expansion of a gas into an evacuated space is a spontaneous process. The reverse process-gas molecules initially distributed evenly in two flasks all moving into one flask-is not spontaneous.If flask B were smaller than flask A, would the final pressure after the stopcock is opened be greater than, equal to, or less than 0.5 atm?

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We are given the following figure:

A diagram shows two flasks, connected by a closed stopcock.  Flask A on the left has gas at 1 atmosphere, while flask B on the right is an evacuated flask at 0 atmospheres. When the stopcock opens, the gas expands to occupy both flasks.  Both flasks A and B now have 0.5 atmospheres of pressure; this process is spontaneous. A third diagram shows the stopcock still open, but all gas molecules have moved back into flask A. This process is not spontaneous.


We are asked if flask B were smaller than flask A, would the final pressure after the stopcock is opened be greater than, equal to, or less than 0.5 atm.

Recall that the ideal gas law is:


PV=nRT


The pressure and volume of a gas are related to the number of moles, gas constant and temperatureThe value nRT is constant


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Problem Details

A diagram shows two flasks, connected by a closed stopcock.  Flask A on the left has gas at 1 atmosphere, while flask B on the right is an evacuated flask at 0 atmospheres. When the stopcock opens, the gas expands to occupy both flasks.  Both flasks A and B now have 0.5 atmospheres of pressure; this process is spontaneous. A third diagram shows the stopcock still open, but all gas molecules have moved back into flask A. This process is not spontaneous.
Expansion of a gas into an evacuated space is a spontaneous process. The reverse process-gas molecules initially distributed evenly in two flasks all moving into one flask-is not spontaneous.

If flask B were smaller than flask A, would the final pressure after the stopcock is opened be greater than, equal to, or less than 0.5 atm?

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Our tutors have indicated that to solve this problem you will need to apply the Chemistry Gas Laws concept. You can view video lessons to learn Chemistry Gas Laws. Or if you need more Chemistry Gas Laws practice, you can also practice Chemistry Gas Laws practice problems.

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Based on our data, we think this problem is relevant for Professor Rhandir's class at GCU.