Question 657390: Hi,
I am so stuck on half lives of Radioactive isotope in science. I thought I had the correct answer to these questions, but they are not. Please help me.
I need to know if you have 2 grams of Carbon-14, after 5760 years there would be how many grams left?
If you how 2 grams of Carbon-14, after 11520 years there would be how many grams left?
If you have 2 grams of Carbon-14, after 23040 years there would be how many grams left?
Please break this down to me. I am SO comfused. Thanks
Found 2 solutions by ewatrrr, htmentor:
Answer by ewatrrr(24785)   (Show Source):
Answer by htmentor(1343)  (Show Source):
You can put this solution on YOUR website! The half-life of a radioactive element is the amount of time it takes for half of the atoms to decay.
This means that if we start with 1 gram of an element, after one half-life there will be 0.5 grams left.
Assuming the half-life of Carbon-14 is 5760 years, if we start with 2 grams then
after t=5760 years (one half-life), there will be 1 gram left.
Since with each half-life we lose half of the remaining amount, if t=11520 years this is equal to two half-lives, so there will be 0.5 grams left.
In general, we can write N = N0(1/2)^n where N0 is the initial amount and n is the number of half-lives
N0 = 2 grams in this case
t=23040 years is four half-lives, so the amount remaining is 2(1/2)^4 = 0.125 grams.
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