Question

How many mg (to 3 decimal places) of I-131 with half life of 8.07 days remain from a 5.0 mg sample after 15.6 days?

Answer 1

Amount of substance remains after n half-lives = a/2^n

a = intial amount

n = number of half-lives.

n = total time/half-life time

   = 15.6/8.07

   = 1.933

Amount of substance remains after n half-lives = 5.0/2^1.933

                                                                          = 1.309 mg