Question

If you had a 100-gram sample of plutonium, how much would still remain in 43 years?

Answer 1

`m_r~=11.9 \ grams`

Explanation:

What is missing from the question is the identity of the specific isotope present in the 100-gram sample - I would assume it is plutonium - 241 that has an average half-life of 14 years, the shortest among the plutonium isotopes family.

`n " is the number of periods "`

`n=(time)/("half-life")`

`n= (43 \ "years")/ (14 \ "years")~=3.07`

`m_i=m_rxx2^n`

`m_i=" is the initial mass"`

`m_r=" is the remaining mass after n periods"`

`m_r=m_i/2^n`

`m_r=100/2^(3.07)`

`m_r~=11.9 \ grams`