The isotope phosphorus 30 has a half-life of 2.5 minutes you need a 4 g scale of this isotope for an experiment which will take you approximately 15 minutes to prepare in order to have 4 g with experiment begins how much phosphorus 30 should you start with

256g oh phosphorus 30

Explanation: since the half life is 2.4 min, that mean the mass of phosphorus 30 reduced by half every 2.5 min from a certain amount. That is,

T1/2 = 2.5 min

Amount of time the phosphorus disintegrated into two is nT1/2,

30/2.5 = 6 half lives

Amount left after 6 half lives n = 4g

Inittial amount started with = N =?

Using N = n x 2^nT1/2

N = 4 x 2^6 = 4 x 64

N = 256g