Carbon-14 Decay: Dose We Receive from Natural Radiation

[stephaniek]

The radiocarbon in our bodies is one of the naturally occurring sources of radiation. Let's see how large a dose we receive. ¹⁴C decays via B^- emission, and 18.0% of our body's mass is carbon.

a) Write out the decay scheme of carbon-14 and show the end product. (A neutrino is also produced.)
answer: ¹⁴₆C ------> e^- + ¹⁴₇N + v_e

b) Neglecting the effects of the neutrino, how much kinetic energy (in MeV ) is released per decay? The atomic mass of C-14 is 14.003242 u.
No idea where to begin tried using E = mc² did not get the right answer.

c) How many grams of carbon are there in a 76.0 kg person?
no idea how to do this.

d) How many decays per second does this carbon produce? (Hint: Assume activity of C-14 is about 0.255 Bq per gram of carbon.)
No idea about this one either.

Any help would be greatly appreciated.

 

[hamster143]

How many grams of carbon are there in a 76.0 kg person?
no idea how to do this.

Carbon is 18.0% of body mass. 76.0 times 18.0%.

How many decays per second does this carbon produce? (Hint: Assume activity of C-14 is about 0.255 Bq per gram of carbon.)
No idea about this one either.

Look up the definition of Bq (Becquerel) in Wikipedia.

 

[arivero]

It seems that it is a problem allowing you to use tables. Obviously to use E=mc2 (how do you pretend use it, anyway?) you need the mass difference between carbon and nitrogen. The data of the atomic mass of C-14 is in part a need and in part a red herring (so naive people will try to apply E=mc2 to it, instead asking the tables for the atomic mass of N-14 too).

The radiocarbon in our bodies is one of the naturally occurring sources of radiation. Let's see how large a dose we receive. ¹⁴C decays via B^- emission, and 18.0% of our body's mass is carbon.

a) Write out the decay scheme of carbon-14 and show the end product. (A neutrino is also produced.)
answer: ¹⁴₆C ------> e^- + ¹⁴₇N + v_e

b) Neglecting the effects of the neutrino, how much kinetic energy (in MeV ) is released per decay? The atomic mass of C-14 is 14.003242 u.
No idea where to begin tried using E = mc² did not get the right answer.