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March 25, 2017

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A fossil is found to have a C-14 level of 86% compared to living organisms. How old is the fossil?, (the half life of C14 is 5730 years).

  • Chemistry - ,

    k = 0.693/t1/2
    ln(No/N) = kt
    I would use 100 for No
    and N = 86
    k from above
    solve for t in years.

  • Chemistry - ,

    I thought about that, but didn't know the initial and remaining N. Why initial N is 100?

  • Chemistry - ,

    It's a convenient number to pick. You can start with any number you wish as long as you make N = 0.86*No. So it's easy to pick 100% for No which makes N = 86.

  • Chemistry - ,

    The hint they gave us now is that this is a first intigrated order reaction, I do not get it, what the order of the reaction has to do with nuclear chemistry and decay?

  • Chemistry - ,

    The first is the fact that all nuclear decay reactions are first order. That tells you that you can use the ln(No/N) = kt equation and that k = 0.693/t1/2.
    Other orders have different equations for t1/2 and for time for x amount to decay. In kinetics it makes little difference if we are talking about decay of a radionuclide or decay of N2 and O2 is a reaction of N2 + O2 ==> 2NO except that radionuclide decay is always first order and other reactions may be second order or third order.

  • Chemistry - ,

    Thanks, I got it right.

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