Calculating the Decay Constant of Carbon 14

In summary: It seems like you are on the right track with your calculations, but remember to use the correct formula for decay constant: λ = 0.693/T1/2. This means that the decay constant for Carbon 14 is approximately 0.000121 s^-1. In summary, the conversation discusses the half life and decay constant of Carbon 14, with the goal of calculating the decay constant using the Avogadro constant and a given formula.
  • #1
EIRE2003
108
0
Carbon14 has a half life of 5730 yrs. This is the only information i am given.

Caluculate the decay constant of Carbon 14.

This is what I have done.

dN/dt = -lambda(N)

I know the Avogadro Constant is equal to 6x10^23

So i am using 1kg in my formula.

14C = 6 x 10^23 x 1000/14

where do i go from here??
 
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  • #2
Half life and decay constant are just two ways of expressing the rate of radioactive decay. Half life (T) uses a base of 2:
[tex]X = X_0 2^{-\frac{t}{T_{half}}}[/tex]

Decay constant (λ) uses a base of "e":
[tex]X = X_0 e^{-\lambda t}[/tex]

You can convert from one to the other. Hint: [tex]2 = e^?[/tex]
 
  • #3
ok i used dN/dt

which is 0.693 x 6 x 10^23/5730x 360 x 24 x 3600 x 14
which is equal to 3 x 10^28 s^-1

Is that right??
 
  • #4
Remeber that 1/λ is going to be equal to the mean lifetime of a C-14 particle, your figure gives a mean lifetime of about 3 x 10^-29 seconds, the mean lifetime is always longer than the half-life so the anbswer MUST be wrong.

Use Dr. Al's hints.
 
  • #5
Avogadro's number is irrelevant.
[tex]2 = e^{0.693}[/tex]
so... [itex]\lambda = \frac{0.693}{T_{half}}[/itex]
 
  • #6
Ah i don't understand it.
Im looking at an example in a book and it has the second formula he gives,

ie N=No e^-lambda t

therefore dN/dt=-No Lambda e ^-lambda t = - lambda N

When N =12, dN/dt = -lambda 10^12

Now lambda = 0.693 / T1/2
 
  • #7
decay rate vs. decay constant?

Perhaps you are confusing decay rate (which is dN/dt) with decay constant (which is λ)?
 

FAQ: Calculating the Decay Constant of Carbon 14

1. How is the decay constant of carbon 14 calculated?

The decay constant of carbon 14 is calculated using the equation λ = ln(2)/t1/2, where λ is the decay constant, ln is the natural logarithm, and t1/2 is the half-life of carbon 14.

2. What is the half-life of carbon 14?

The half-life of carbon 14 is approximately 5,730 years. This means that after 5,730 years, half of the original amount of carbon 14 in a sample will have decayed into stable carbon 12.

3. Why is the decay constant of carbon 14 important?

The decay constant of carbon 14 is important because it allows us to determine the age of organic materials through radiocarbon dating. By measuring the amount of carbon 14 remaining in a sample and using the decay constant, we can calculate how long ago the organism died.

4. How accurate is the calculated decay constant of carbon 14?

The calculated decay constant of carbon 14 is highly accurate, with a margin of error of only 1-2%. This is because the half-life of carbon 14 has been extensively studied and measured, leading to a precise understanding of its decay rate.

5. What factors can affect the calculated decay constant of carbon 14?

The calculated decay constant of carbon 14 can be affected by external factors such as changes in the Earth's magnetic field, fluctuations in cosmic radiation, and contamination of the sample. It is important to consider these factors when using radiocarbon dating to determine the age of a sample.

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