Question

The half life of a radioactive element X is 5days, if there is 5g of X initially, what will be the mass of X after a.) 5 days b.) 20days c.) 40days

Answer 1

just using the definition of "half"-life,

(a) 5 * 1/2 = 5/2
(b) 5 * (1/2)^4 = 5/16
(c) 5 * (1/2)^8 = 5/256