Question

the half life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced by half its initial mass. starting with 125 grams of a radioactive isotope how much will be left after 6 half lives

Answer 1

Okey, we are going to use the hlaf life formula, let's do it:

$Nn=N_0(\frac{1}{2})^n$

Where:

N=6

Nn = quantity remaining after n half-lifes

No = initial quantity=125

Replacing we obtain:

$N_6=125(\frac{1}{2})^6=125(\frac{1}{64})\approx1.95$

Finally we obtain that the radioactive isotope will have 1.95 grams after 6 half lives.