The half-life of iodine -125 is 60 days. What fraction of iodine-125 would be left after 180 days?
my teacher didn't teach us this and expects us to know it and I don't understand!!!
could you explain it please!?
The half life of a material is the time it takes for exactly 1/2 of the material you started with to disintegrate into another material. In this case, the half life is 60 days. Therefore, 1/2 will be left after 60 days, 1/2 of the 1/2 (that is 1/4) will be left after 120 days (a second half life) and 1/2 of the 1/4 (=1/8) will be left after 120 days (the third half life).
The amount left is 1/2n where n is the number of half lives.
1/2n = 1/23 = 1/8
Sure! I'd be happy to explain it to you.
The half-life of a radioactive substance is the time it takes for half of the substance to decay. In this case, the half-life of iodine-125 is 60 days.
To find out what fraction of iodine-125 would be left after 180 days, we need to determine how many half-life periods have passed.
If the half-life is 60 days, we can calculate the number of half-life periods by dividing the total time (180 days) by the half-life:
Number of half-life periods = Total time / Half-life = 180 days / 60 days = 3
So, after 180 days (or 3 half-life periods), the fraction of iodine-125 remaining can be calculated as (1/2)^n, where n is the number of half-life periods.
In our case, n = 3, so the fraction of iodine-125 remaining after 180 days is:
Fraction remaining = (1/2)^3 = 1/8
Therefore, after 180 days, only 1/8 or 12.5% of the original amount of iodine-125 would be left.
Of course, I can explain it to you! Understanding the concept of half-life and how to calculate the remaining fraction of a substance is important in various scientific fields, including chemistry and nuclear physics.
In this case, the half-life of iodine-125 is given as 60 days. The half-life represents the time it takes for half of the original amount of a radioactive substance to decay.
To determine the fraction of iodine-125 remaining after a certain period, such as 180 days, you need to calculate the number of half-lives that have occurred.
Here's how you can do it step by step:
1. Determine the number of half-lives that have passed:
- Divide the total time elapsed (180 days) by the half-life (60 days) of iodine-125.
180 days ÷ 60 days = 3 half-lives
2. Calculate the fraction remaining:
- The fraction remaining can be found using the formula: Remaining fraction = (1/2)^(number of half-lives).
- Substitute the number of half-lives we calculated earlier into the formula:
Remaining fraction = (1/2)^(3)
Remaining fraction = 1/8
Therefore, after 180 days, only 1/8 or 0.125 (which is the decimal equivalent) of the original amount of iodine-125 would remain.
I hope this explanation helps you understand how to calculate the remaining fraction of a substance with a given half-life. If you have any further questions, feel free to ask!