Half-Life

We can use this formula:

A = A₀ * 2 ^-t/h      where A  is the amount left after t hours   A0 is the original amount    and h is the half-life in hrs.  ....so we have....

A = 18 * 2 ^-60/15    

A = 18 * 2^-4       

A = 18/ 16   =   9/8  grams 

Sodium-24 has a half-life of 15 hours. How much sodium-24 will remain in an 18.0 g sample after 60 hours?

60/15=4 half-lives,

2^-4 X18=1.125 grams of Sodium-24 left after 60 hours.