Math Is Fun Forum

fusilli_jerry89

Member

Registered: 2006-06-23

Posts: 86

Carbon 14 Half-Life

Suppose that a fraction of mass, 1.00 x10^-12, of terrestrial carbon in living organisms is not carbon 12, but carbon 14, which has a half-life of 5730 years. How many counts per second would you expect from 3.35 kg of pure carbon made from wood taken from a young living Douglas fir tree when u place the material in a well-shielded beta detector?

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Carbon 14 Half-Life

Here's some info you can use to aid you in your endeavour:

  When Carbon 14 emits a beta particle, the Carbon 14 atom becomes a Nitrogen 14 Atom.

The radiation is actually quite small. There are only 13.6 disintegrations per GRAM of Carbon per minute, but just use this as a check after you are done...

one mole of carbon is 12.0107 grams, see periodic table.
In addition to errors associated with instrumentation, the average mass of a molecule is subject to variations in the isotopic abundances of its constituent elements. Natural isotopic abundances depend on the source of the material. For this reason, the average atomic weight of carbon, 12.0107±0.0008, can only be quoted with fairly limited precision.

6.022141 E23 is # of atoms in one mole.

12.0107 amu
Carbon-13    13.003355    1.1%
Carbon-12    12        98.9%

Last edited by John E. Franklin (2007-09-18 09:47:44)

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