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Homework Help: Chem Question on ENERGY

  1. Nov 24, 2004 #1
    I'm really stuck on this question:

    What will be the final temperature if 50.0 g of steam at 100 degrees celsius is mixed with 600 mL of water at 10.0 degrees celsius? (Answer: 58.3 degrees celsius)

    So far I've got:

    heat lost (steam) = heat gained (water)
    nH + mc(delta)t = mc(delta)t

    Sorry I don't know how to make the delta symbol.

    (500g/18.02g/mol)(40.65 kJ/mol) + 0.500 kg(2.02 kJ/kg*C)(100-t) = 0.600 kg(4.19 kJ/kg*C)(t-10)

    When I calculated everything, I didnt' get 58.3*C, so maybe someone can tell me where I went wrong in either my formulas or calculations. Thanks.
  2. jcsd
  3. Nov 24, 2004 #2
    You used the specific heat capacity of steam, but after the phase change, it is water that is being cooled and no longer steam.
  4. Nov 25, 2004 #3
    Try to assume that all the steam became liquid water after mixing with water.
    If the value of temperature is above 100, then there are some steams left.
  5. Nov 25, 2004 #4
    I got the answer now....I forgot that after when steam goes through a phase change, it is now water, not steam. Now my answer matches in one in the book. Thank you!
  6. Nov 25, 2004 #5
    This is the question that I'm actually really having trouble cause I don't have a clue where to start. I think this is one of those really nasty questions.

    Calculate the final temperature when 100 g of ice at -10.0*C are added to 30.0 g of steam at 110*C.

    I actually sort of know where to start....but yeah, I'm very stuck on this one...
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