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Find the mass of ethyl alcohol

  1. Jun 22, 2009 #1
    1. The problem statement, all variables and given/known data

    What is the initial temperature of copper if, 11 g aluminum at 200 C and 21 g of copper are dropped into 46 cm^3 of ethyl alcohol at 15 C. The final temperature of the system is 22 C.




    2. Relevant equations

    Q=McT

    3. The attempt at a solution

    My work : Qal+Qcu+Qea=0, and solved for the intial temperature. I got -130 C which was wrong. To find the mass of ethyl alcohol, i used volume and density. Volume is 790 kg/m^3
     
  2. jcsd
  3. Jun 22, 2009 #2

    mgb_phys

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    Re: Calorimetery

    Try converting everything into the same units (eg kg)
     
  4. Jun 22, 2009 #3
    Re: Calorimetery

    i converted everything and got this forumla

    m1 * s1 * t1 + m2 * s2 * t2 + = m1 * s1 * tf + m2 * s2 * tf + m3 * s3 * tf

    m1= aluminum
    m2=coppper
    m3=ethtyl alcohol,

    i just cant get the write answer.
     
  5. Jun 22, 2009 #4

    mgb_phys

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    Re: Calorimetery

    In Q=mcT , 'T' is the change in temperature
     
  6. Jun 22, 2009 #5
    Re: Calorimetery

    yea, i took that into account, so i did heat loss=heat gained, and the heat lost was by the aluminum, and i know the ethyl alcohol gained heat, but im not sure what side the copper would go on
     
  7. Jun 22, 2009 #6

    mgb_phys

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    Re: Calorimetery

    Al goes from 200 to 22
    Cu goes from T to 22
    Ethyl goes from 15 to 22

    So
    m_al * c_al * (200-22) + m_cu * c_cu * ( T-22) + m_eth * c_eth * (15-22) = 0
     
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