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The drawing shows two thermally insulated tanks. They are connected by a valve that i

  1. Sep 19, 2010 #1
    The drawing shows two thermally insulated tanks. drawing: http://www.webassign.net/CJ/14_26.gif
    They are connected by a valve that is initially closed. Each tank contains neon gas at the pressure, temperature, and volume indicated in the drawing. When the valve is opened, the contents of the two tanks mix, and the pressure becomes constant throughout.

    (a) What is the final temperature? Ignore any change in temperature of the tanks themselves.(Hint: The heat gained by the gas in one tank is equal to that lost by the other.)
    _______K
    (b) What is the final pressure?
    _______Pa
    I have stared at this picture for like 30 minutes and read the entire chapter on thermodynamics in my physics book but I can't find a solution. Please provide one, thank you.
     
  2. jcsd
  3. Sep 19, 2010 #2

    ehild

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    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    Find quantities which are conserved during the experiment for this system of two tanks. Opening the valve will not change the overall volume. The gas does not escape. There is no exchange of energy with the surroundings...

    ehild
     
  4. Sep 19, 2010 #3
    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    do i use the formula that Q=cmdeltat
     
  5. Sep 19, 2010 #4

    ehild

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    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    If you know m and c and Q... Do you know them?

    ehild
     
  6. Sep 19, 2010 #5
    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    i think i should answer yes, however i dont know the mass of neon gas. is it going to be the molecular mass?
     
  7. Sep 19, 2010 #6

    ehild

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    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    You can not answer yes. In principle, the specific heat capacity is given either for constant volume or for constant pressure. If you look at the data, the gas in the tanks is at different pressure. When the valve is opened, some gas flows from one tank to the other, so the volume of the gas changes, and so does its pressure.

    Use the ideal gas law to find the amount of gas in both tanks.

    ehild
     
  8. Sep 19, 2010 #7
    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    well the ideal gas law is pv=(m/M)RT and R=8.31 but how do i use this equation
     
  9. Sep 19, 2010 #8

    ehild

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    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    Use the form with moles, n : pV=nRT. You know p, V and T for both tanks you can calculate the number of moles they contain.

    ehild
     
  10. Sep 19, 2010 #9
    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    okay so after i get the moles in each tank what do i do?
     
  11. Sep 19, 2010 #10

    ehild

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    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    After opening the valve you have one container with volume equal to the sum of both tanks, and the amount of gas equal to the sum of the moles initially present in both tanks. You can write the idel gas law for this container, too.

    You can do the same with the internal energy. It is the sum of the initial internal energies of both tanks.

    ehild
     
  12. Sep 19, 2010 #11
    Re: The drawing shows two thermally insulated tanks. They are connected by a valve th

    now you lost me. i don't know how to calculate the internal energy give just the moles
     
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