To do these problems you start by taking the amount you start with in this case 38 grams and divide it by the time. I'll show you how to do one and hopefully you can do the rest
38grams/8 days = 2grams/day
(1/2)^2gams/day = .25
38 grams x .25 = 9.5g remaining after 8 days
If the half-life of iodine-131 is 8 day, how much would remain undecayed after 8 day if we started with 38 grams?
How much at 16 days?
24 days?
32 days?
2 answers
amount = 38 (1/2)^(t/8)
clearly after 8 days , we would have 38(1/2)^1 = 19 g
after 16 days:
amount = 38(1/2)^(16/8
= 38(1/2)^2
= 38/4 or 9.5 g
repeat for the other two cases
clearly after 8 days , we would have 38(1/2)^1 = 19 g
after 16 days:
amount = 38(1/2)^(16/8
= 38(1/2)^2
= 38/4 or 9.5 g
repeat for the other two cases
4 answers