Posted by Mima on Friday, April 27, 2012 at 9:00pm.
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 - DrBob222, Friday, April 27, 2012 at 9:35pm
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 - Mima, Saturday, April 28, 2012 at 12:34am
I thought about that, but didn't know the initial and remaining N. Why initial N is 100?
Chemistry - DrBob222, Saturday, April 28, 2012 at 12:53am
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 - Mima, Saturday, April 28, 2012 at 9:55am
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 - DrBob222, Saturday, April 28, 2012 at 3:39pm
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 - Mima, Saturday, April 28, 2012 at 5:01pm
Thanks, I got it right.
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