HELP NEEDED.

Question

The half-life of iodine-131 is 8 days. If a sample originally contains 0.96 g of the isotope, how much will remain after 24 days?
A. 0.24 g

B. 0.12 g

C. 0.06 g

D. 0.48 g

Answer 1

Half-life is the time required for the amount of something to fall to half its initial value.

 

In your example, you are told that the half-life is 8 days.  This means every 8 days you lose half of its initial value.

 

Thus, after 8 days your .96 g is halved to .48 g and you have used 8 of your 24 days leaving you 16 more days to account for.

 

After a second 8 days, you will have half of the remaining .48 g leaving you with .24 grams.

 

After the final 8 days, you will have half of that remaining .24 g leaving you with .12 grams and the answer.

 

b) .12 grams.