If the half-life of iodine-131 is 8 days, how much of a 5-g sample is left after 32 days?

1 Answer

0.3125\ g

Explanation:

The half life T_{\text{1/2}} is the period of time after which the amount of radioactive element becomes half of its original amount

The amount left N after n half lives of a radioactive element with original amount N_0 is

N=N_0(1/2)^n

Given that half life of Iodine-131 is 8 days hence the amount left N after 32 days i.e. n=32/8=4 half lives taking initial amount N_0=5g

N=5(1/2)^4=5/16=0.3125\ g