Question

Half life questions. I know what it means but I'm stuck starting off on it.

2. A 2.5 gram sample of a radioactive element was formed in a 1960 explosion of an atomic bomb at Johnson lsland in the Pacific test site. The half life of the element is 28 years. How much of the element will remain after 112 years?

3. An element has a half life of 29 hours. If 100 mg of the element decays over a period of 58 hours how many mg will remain?

Answer 1

ok so for 2, would it be 4 half lives. so the first half life would be 1.25. the 2nd half life would be 0.625. the third half life would be 0.3125. and the fourth half life would be 0.15625. so after 112 years, only 0.15625 grams of the element will remain. Am I doing this right?

Answer 2

How did you get those numbers ? @taylorvengam

Answer 3

I multiplied 2.5 by .5 and then each number after that @Shay17

Answer 4

I think this will help you
I can't give you the answer but this will seem to be the correct way to do it @taylorvengam
https://www.youtube.com/watch?v=ekoQTOI_9js

Answer 5

It's not that simple I don't think you're following the right steps

Answer 6

@aaronq can you help ?

Answer 7

#1 is good. you can also use this formula \(A_o(1/2)^n\)

where \(A_o\) is the initial amount, and n is the amount of half-lives passed.

#2 is pretty much the same thing

Answer 8

I agree with @aaronq
You just have to know what the formula is but that video can help you for future reference

Answer 9

Good luck

Answer 10

thank you both! @Shay17 @aaronq