Question

What fraction of radioactive atoms remains in a sample after six half-lives?

Answer 1

Answer :  $\frac{1}{64}$ of radioactive atoms remains in a sample after six half-lives.

Solution:

Formula used :

$a=\frac{a_o}{2^n}$

where,

a = amount of reactant left after n-half lives = ?

$a_o$ = let Initial amount of the reactant = x g

n = number of half lives= 6

Putting values in above equation, we get:

$a=\frac{x}{2^6}$

$a=\farc{x}{64}$

Therefore, $\frac{1}{64}$ of radioactive atoms remains in a sample after six half-lives.