Question

What percentage of a radioactive substance remains after 7.00 half-lives have elapsed?0.391%1.56%3.12%0.78%

Answer 1

Answer:

Percentage of a radioactive substance remains after 7.00 half-lives have elapsed is 0.78%.

Explanation:

Formula used :

$A=\frac{A_o}{2^n}$

where,

A = amount of reactant left after n-half lives

$A_o$ = Initial amount of the reactant

n = number of half lives

We have:

n = 7.00

$A=\frac{A_o}{2^7}$

$\frac{A}{A_o}=\frac{1}{128}$

Percentage of a radioactive substance remains after 7.00 half-lives have elapsed:

= $\frac{1}{128}\times 100=0.78%$