Question

If 130 days have passed approximately how many grams of iodine-125 will remain?

Answer 1

Hello!

The half life (the amount of time it takes for half of an element to decay) of iodine here is 60 days. This is because we see that the original mass is 600g, and after 60 days, it drops to 300g.

Now, set up an equation. Let y = mass of iodine, and x = # of 60 days passed.

$y = 600 (.5)^{x}$

Now, we know that we are looking for 130 days. To find x, divide 130 by 60.

130 / 60 = 2.167 (approximately)

Now, set x = 2.167 and solve for y.

$y = 600 (.5)^{x}$

$y = 600 (.5)^{2.167}$

$y = 600 (.5)^{2.167}$

$y = 600 (0.222673225)$

$y = 133.603935$

Therefore, your solution is about 134 grams of iodine-125 will remain.

Hope this helps!