9. Assume you began with 10 g of a radioactive parent isotope. How many grams of parent isotope will be present in the same sample after 2 half-lives?
A. 5.0 g
B. 2.5 g
C. 1.25 g
D. 0.63 g
Is it A???
no, 5 is 1/2 of 10, so that is what's left after one half-life
You want half of that.
Okay, thank you.
To find the amount of parent isotope remaining after 2 half-lives, we need to halve it for each half-life.
Given that you started with 10 g of the parent isotope, after the first half-life, you would have 5 g remaining. After the second half-life, you would have half of that amount, which is 2.5 g.
So, the correct answer is B. 2.5 g.
To determine the answer, we need to understand the concept of half-life. The half-life of a radioactive isotope is the time it takes for half of the parent isotope to decay into its daughter isotope.
In this case, we are given that the initial amount of the parent isotope is 10 grams, and we want to find out how much will be present after 2 half-lives.
After one half-life, half of the parent isotope will decay, leaving behind 5 grams of the parent isotope.
After the second half-life, half of the remaining 5 grams will decay, leaving behind 2.5 grams of the parent isotope.
Therefore, the correct answer is B. 2.5 g