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Homework Help: Physics H.W.

  1. May 31, 2004 #1
    Problem 2. Liquid nitrogen, which has a boiling point of
    77 K, is commonly used to cool substances to
    low temperatures.
    How much energy must be removed from
    1.4 kg of gaseous nitrogen at 77 K for it to
    completely liquefy? Assume the latent heat
    of liquid nitrogen is 2.01 *10^5 J/kg Answer
    in units of J.

    Problem 4.
    You have collected exactly 2200 aluminum
    cans for recycling, each with a mass of 14.1 g.
    How much energy is needed to melt them if
    their initial temperature is 26.8 degrees C? Assume
    the specific heat, the latent heat and the
    melting point of aluminum are 899 J/kg * degrees C,
    3.97*10^5 J/kg and 660.4degreesC respectively. An-
    swer in units of J.
  2. jcsd
  3. May 31, 2004 #2


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    Staff Emeritus
    Science Advisor
    Gold Member


    You've been here long enough to know you should post what you've tried when asking for help.
  4. Jun 2, 2004 #3
    how much homework have you done...
  5. Jun 2, 2004 #4
    1600J and 3200J

    The answers reflect how much effort you put into trying to solving your homework :tongue2:
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