Question

Strontium-90, a radioactive isotope with applications in medicine, has a half-life of approximately 30 years. Out of a 100-gram sample, approximately how much remains after 170 years? 2 grams 8 grams 17 grams 81 grams

Answer 1

There are 2 grams remain

Further explanation

Given

t1/2 = 30 years

t = 170 years

No = 100 g

Required

Remaining sample

Solution

General formulas used in decay:  

$\large{\boxed{\bold{N_t=N_0(\dfrac{1}{2})^{t/t\frac{1}{2} }}}$

Input the value :

$\tt Nt=100.\dfrac{1}{2}^{170/30}\\\\Nt=1.969\approx 2~grams$