chemistry help!!!!!?

Question

ok, so im sort of stuck on the last question. please help!!!

the carbon-14 isotope is radioactive and undergoes beta decay. the half life of the carbon-14 isotope is about 5700 years.

a) give the atomic number and the mass number of the species formed when carbon-14 undergoes beta decay.

b) how much of a 20g sample of carbon-14 would remain after 17190 years? please show how you get your answer.

c) the presence of the carbon-14 isotope is used to date old materials such as wooden boats and fabrics such as the "turin shroud" explain why the carbon-14 isotope is very suitable choice for dating such materials.

thanks :)

Answer 1

a) C-14 --> ß + N-14

b) t1/2 = ln(2)/l l = ln(2)/5700 = 1.2 *10^-4

N(t) = Ne-lt

N(t) = 20g e(-1.2*10-4*17190) = 2.5 g

c) The current maximum radiocarbon age limit lies in the range between 58,000 and 62,000 years (approximately 10 half-lives). This limit is encountered when the radioactivity of the residual 14C in a sample is too low to be distinguished from the background radiation.

It is my understanding that C14 dating is accurate in these artifacts only because they are relatively new to the current background radiation detection limits. C-14 has a relatively short 1/2 life, and with mans atomic testing and other solar events, the population C-14 will and may have changed in time to some effect, making the dating unreliable.

I think that is why it is used with some degree of latitude when giving exact dates; there is more about it in the wiki reference..

ref: http://en.wikipedia.org/wiki/Carbon_dating

Answer 2

Carbon-14 is a radioactive isotope, which decays with a given half-life.
The decay rate of the half-life will be known.
From the decay rate and the current level of radioactivity, an age can be estimated.

Answer 3

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Answer 4

a) Nitrogen 14 (Atomic No 7)
b) Do you mean 17100 years? If so 17100 is 3 x half life, so 0.5 * 0.5 * 0.5 *20g would remain = 2.5g
c)See the wikipedia for more about carbon dating