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Free energy from Thorium to Radon

  1. Jun 12, 2009 #1
    228 224 4
    Th --> Ra + He
    90 88 2


    228,031015u --> 224,020186u + 4,0026033u

    228,031015u - [224,020186u + 4,0026033u]=

    0,0082257u

    0,0082257u x 931.49 MeV = 7662157,293eV

    7662157,293eV x (1.602 x 10^-19J) =

    1,2274776 x 10^-12J

    Svar: Frigjorda energin är: ~ 1.23 x 10^-12J


    Hi, people could anyone check what I've done wrong here??? My teacher says the answer value is a bit too high. It's just arithmetic and I've still done something wrong...


    I tried multiplying the (0,0082257u) with (1.66 x 10^-27) x C^2 and I still get ~ 1.23 x 10^-12J

    Thanks.
     
    Last edited: Jun 12, 2009
  2. jcsd
  3. Jun 12, 2009 #2

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    Your answer appears to be right.

    From E = mc^2:

    Just multiply the mass difference in kg. by c^2 in m/sec. to get the energy in joules

    Mass difference is 8.226x10^-3 amu. One kg = 1000 x 6.02x10^23 amu so one amu = 1.66 x 10^-27 kg. Multiply that by (3 x 10^8 m/sec)^2 to get the energy in J. per amu. (= 1.49 x 10^-10 J.). So that works out to 8.266x10^-3 x 1.49 x 10^-10 = 12.3 x 10^-13 J = 1.23x10^-12 J.

    AM
     
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