pressure and volume...

[mak10]

flask X contains 1 dm3 of helium at 2 kPa pressure and flask Y contains 2 dm3 of neon at 1 kPa pressure. if the flasks are connected at constant temperature, what is the final pressure?

 

any ideas on how to solve this??

 

-mak10

[swansont]

At constant T, PV is also constant. In a mixture, partial pressures add to be the total pressure.

[mak10]

partial pressures added gives 3 kPa... but the correct answer is different.

 

-mak10

[jdurg]

Correct. That's because the overall volume has changed. So if you use P1V1 = P2V2 you can calculate the pressure of each gas at the new volume. Then you add up the partial pressures and you have your answer. (I got 4/3 kPa.)

[mak10]

i still dont get it. whats the new volume? how did you get it? your answer is correct.... it is 4/3 kPa... but can you show me, briefly, the exact steps you took to get this answer? am confused... thanks jdurg!

 

-mak10

[jdurg]

i still dont get it. whats the new volume? how did you get it? your answer is correct.... it is 4/3 kPa... but can you show me' date=' briefly, the exact steps you took to get this answer? am confused... thanks jdurg!

 

-mak10[/quote']

 

 

Sure. According to your initial post, the total volume will be 3 dm^3. This is what you get by adding the volume of gas 1 to the volume of gas 2. Since the flasks are connected, the overall volume will be the sum of the volume of the two flasks. To get the pressures, I just used P1V1 = P2V2 and figured out the new pressure of each gas.

 

Gas X; (2kPa)(1 dm^3) = P2(3 dm^3). P2 = 2/3 kPa.

 

Gas Y; (1kPa)(2 dm^3) = P2(3 dm^3). P2 = 2/3 kPa.

 

So the partial pressure of each gas is 2/3 kPa. The total pressure is the sum of the partial pressures, so you just add the two partial pressures and get 4/3 kPa.

[mak10]

ingenious... thanks a lot jdurg!

 

-mak10