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Thermodynamics question

  1. Mar 5, 2010 #1
    1. The problem statement, all variables and given/known data
    A well insulated piston-cylinder device contains 4kg of liquid water and 1kg of water vapour at 120C and is maintained at constant pressure. Now a 5kg copper block at 30C is dropped into the cylinder. Determine the equilibrium tempurature once equilibrium is established.

    The answer should be 120C apparently

    2. Relevant equations
    H = U + W
    dE = Q - w

    3. The attempt at a solution
    I attempted:
    dE=dU + KE + PE
    dE = dU
    dU = dH - W
    dH - W = Q-W+mihi
    dH = mihi
    But I don't see how what I have done helps......
    Maybe I should deduce the tempurature using just theory
  2. jcsd
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