A 2500 sample of np-239 decays for 30 days. what mass will remain radioactive?

half-life problems

1 Answer
Mar 2, 2018

The mass that will remain is #=0.367u#

Explanation:

The equation for the radioactive decay is

#A(t)=A_0e^(-lambdat)#

#lambda# is the radioactive constant

#lambda=(ln2)/t_(1/2)#

The half life of #"Neptunium-239"# is #t_(1/2)=2.356d#

The initial mass is #A_0=2500u#

The time is #t=30d#

Therefore,

#A(t)=2500e^((-(ln2)/2.356)*30)#

#A(t)=2500e^(-8.826)=0.367u#