[viet]

Given a half-life of an element, Pu (hf = 24,119 yrs) and a value of disintegration per second per liter. How would I find the molarity of Pu in a solution?

I'm not sure what equation to use or how to proceed...
.
after some googling, I use the equation ln(N/N_o) = -kt , k = 0.693/t₂ = 2.87E-5.
say the dpspl was 50, and t = 1 sec
N/50 = e^-2.87E-5(1)
so N = 50*e^-2.87E-5(1) = 49.998 atoms ?
(i dont think it matters if your solving for N or N_o bcuz the half-live is long compare to the dps)
then divide by 6.02×10²³ to get the molarity.
plz correct me if this is wrong.

[Borek]

If anything, 50 is N₀-N.

You need to find the dependence between activity and amount and half life.