In this problem, we are being asked to determine the mass of Strontium-90 remaining when after three half-lives have passed the 50.0 g of sample.
Recall that radioactive/nuclear decay of isotopes follows first-order kinetics, and the integrated rate law for first-order reactions is:
[N]t = concentration at time t
k = decay constant
t = time
[N]0 = initial concentration.
Also, recall that half-life is the time needed for the amount of a reactant to decrease by 50% or one-half.
The half-life of a first-order reaction is given by:
Decay of a 10.0-g sample of strontium-90 (t1/2 = 28.8 yr).The 10 x 10 grids show how much of the radioactive isotope remains aftervarious amounts of time.
If we start with a 50.0-g sample, how much of it remains after three half-lives have passed?