Question

A sample contains 10 g of a radioactive isotope. how much radioactive isotope will remain in the sample after 3 half-lives?

Answer 1

Answer:

1.25 g of radioactive isotope will remain in the sample after 3 half-lives.

Explanation:

Formula used to calculate the number of half life elapsed :

$N=\frac{N_o}{2^n}$

where,

N = amount of radioactive sample remains after n-half lives = ?

$N_o$ = Initial amount of the radioactive sample= 10 g

n = number of half lives  = 3

$N=\frac{10 g}{2^3}=1.25 g$

1.25 g of radioactive isotope will remain in the sample after 3 half-lives.