Question

After decaying for 48 hours, of the original mass of a radioisotope sample remains unchanged. What is the half-life of this radioisotope? 1. 3.0 h 2. 9.6 h 3. 12 h 4. 24 h

Answer 1

The question is incomplete.


The complete question is: After decaying for 48 hours, 1/16 of the original mass of a radioisotope sample remains unchanged. What is the half-life of this radioisotope?



First, calculate how many half-lives have passed to reach 1/16 of the original mass.


Each time that one half-life time passes the mass reduces to half: =>


1 half-life time => 1/2


2 half-life time => 1/4


3 half-life time => 1/8


4 half-life time = > 1/16



Then 4 half-life time correspond to 48 hours, and 1 half-life time corresponds to x:


4 1
---- = -----
48h x


=> x = 48 h * 1 / 4 = 12 h.



Answer: 12 h.