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Homework Help: Liquid Nitrogen

  1. Apr 7, 2005 #1
    So i have been doing thsi question for about a week now and it's about liquid nitrogen. Here it is.

    Liquid nitrogen is used in many low-temperature experiments. It is widely available, and cheaper than gasoline! How much heat must be removed from room temperature (20C) nitrogen gas to produce 1.0 L of liquid nitrogen? The density of liquid nitrogen is 810kg/m^3?

    what id id was i found the amount of moles of nitrogen and used it in the forumla Q=nCvT
    The Cv is a C subscript V which is the molar specific heat capacities of gases. well i don't know what other ways i can do this, so if someone would help that would be great!
  2. jcsd
  3. Apr 7, 2005 #2


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    What is the gaseous nitrogen's specific heat?What is gaseous nitrogen liquifying latent heat?

  4. Apr 7, 2005 #3
    First, the formula you used is accurate only for relatively small temperature changes. The actual formula for a big temp. difference is the integral from T1 to T2 of nCdT. Try doing some web searches for things like heat capacity calculation formulas. I've used one that employed a multi-term series. Do the calculation at various temperatures and sum up the heats for the intervals. There are other ways of doing it, but this one is pretty simple. Also, remember you have to include the heat of vaporization for liquid N2 to get the total heat.
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