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One kg of air is heated in a closed rigid vessel

  1. Nov 3, 2012 #1
    1. The problem statement, all variables and given/known data

    One kg of air is heated in a closed rigid vessel such its temperature changes from 27 C to 427 C . Find the heat transfered
    and change in internal energy .
    Assume : -
    R= 0.287 KJ/kg k
    Cv = 0786 KJ/Kg k


    2. Relevant equations

    Q = mXCX(T2 - T1 )

    3. The attempt at a solution

    please can any one explain to me how I can solve this question

    and is R and Cv must be in same unit

    my answer :

    heat transfer = 1 X 0.786 X 10 (700-300 )

    314.4X 10^3 KJ ( is the unit correct )

    and about second one I don't have any idea for solve it
     
  2. jcsd
  3. Nov 3, 2012 #2
    ΔU=q + w(external)
    w=work
    as you posted Cv then volume is constnt so change in pressure should be taken.so by Gay Lussacs law P=kT
    thereforeP1/P2=T1/T2
    so you can find Work by volume*change in pressure
    add Q to get work
     
  4. Nov 3, 2012 #3
    I don't understand clearly can please help ?
     
  5. Nov 3, 2012 #4
    Since the container is rigid, there is no volume change and no work is done. The heat transferred is equal to the change in internal energy.
     
  6. Nov 3, 2012 #5
    thanks so much
     
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