the half - life of a radioactive kind of nitrogen is 10 minutes. if you start with 120 grams of it, how much…
the half - life of a radioactive kind of nitrogen is 10 minutes. if you start with 120 grams of it, how much will be left after 20 minutes? grams
Answer
Explanation:
Step1: Determine number of half - lives
The half - life is 10 minutes and the time elapsed is 20 minutes. So the number of half - lives $n=\frac{20}{10}=2$.
Step2: Use the half - life formula
The formula for radioactive decay is $A = A_0\times(\frac{1}{2})^n$, where $A_0$ is the initial amount and $n$ is the number of half - lives. Here, $A_0 = 120$ grams and $n = 2$. So $A=120\times(\frac{1}{2})^2$. $A = 120\times\frac{1}{4}=30$ grams.
Answer:
30