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Homework Help: Thermal Expansion of ethanol

  1. May 21, 2010 #1
    1. The problem statement, all variables and given/known data
    1. You pour 108 cm^3 of ethanol, at a temperature of - 10.0 C, into a graduated cylinder initially at 20.0 C, filling it to the very top. The cylinder is made of glass with a specific heat of 840 J/kgK and a coefficient of volume expansion of 1.2 × 10^-5 K^-1; its mass is 0.110 kg. The mass of the ethanol is 0.0873 kg. The specific heat capacity of ethanol is 2428 J/kgK and the coefficient of volume expansion of ethanol is 7.5 × 10-^5 K^-1.
    (a) What will be the final temperature of the ethanol, once thermal equilibrium is reached?
    (b) How much ethanol will overflow the cylinder before thermal equilibrium is reached?

    2. Relevant equations

    m_g c_g (T_f-T_gi )+m_e c_e (T_f-T_ei )=0
    3. The attempt at a solution

    Ive solved them - i really need someone to check them for me, i got - 0.892C for a which i think is right and 0.1cm^3 for b. I am really unsure of b. To solve b i found the expansion of the glass to be -2.71*〖10〗^(-8) m^3 and therefore the final volume to be 1.0797*〖10〗^(-4)m3 then i did the same for the ethanol which i got 7.38*〖10〗^(-8)m3 and 1.0807*〖10〗^(-4)m3 respectively..... from that i found V_loss=V_fe-V_fg and then i got the answer of 0.1 cm3........... any help is appreciated
  2. jcsd
  3. May 21, 2010 #2
    The ethanol is heating up from 10 C and the glass is cooling down from 20 C so you should get a final temperature some where in between so I don't see your final temperature of .89 C. The over flow equals the volume expansion of the ethanol plus the volume contraction of the glass.
  4. May 21, 2010 #3
    sorry thats my bad typing. its heating up from minus 10 degrees and cooling down from 20 degrees and my answer is minus 0.892 degrees. all Celsius for part a.
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